Framebuilders - powdercoat vs. auto paint durability?

Ok, so I want to strip down one of my frames and get it painted.

I can get it powder coated, or I can get it sprayed up at an autobody shop.

Which is going to be more durable? This is for an every day/bad weather commuter bike, so it's gotta be a pretty tough finish. Esthetics come far secondary to durability.

So what say you?
Which is more durable? Auto paint, or powdercoat?

Powder coating will be more durable than paint. Powder coating is especially suitable for every day/bad weather commuting bikes.

a well done wet paint job with a clear coat is pretty durable. Most people that specialize in that kind of paint assert that it is just as durable as powdercoating. However, for no good reason, I suspect a local autobody shop would not do this particularly well

for both powder and paint, the quality of prep work is everything. No matter what, the shop that does a better job stripping and cleaning the frame will give you the best finish. Find a good shop that you trust and woks on bikes regularly and give them you business.

Allan

Powder coat is a tougher material, but it can lift right off parts unless properly applied, and it has a reputation for porosity and not excluding the weather all that well. Rust can actually grow under it.

I agree about quality being the key, but you probably don't want to budget what quality costs. If you can find a nice local powder guy, they will often do a far better job for the bucks than a painter will do. This assumes you are not getting a person with experience in bikes. I think in that case powder has an advantage.

But possibly what you should be considering is which finish is the most repairable. There aren't bulletproof, cheap, finishes for carbon steel bikes. If you want to lean it up against nasty surfaces copy your local bike courier, cheap paint that can be repaired, and lots of tape. I touch up powdercoat with crazy glue, so far it seems to work.

On one of the first frames that I made I had it powdercoated clear, I liked the look at first mostly because the four hundred and some degrees that they pre heat and then bake it at turns the raw metal the color of straw. The bike was a cross bike so it took some abuse , the interesting thing was that every where there was even the smallest nick in the coat , rust would develop underneath the coating and since it was clear, you could see it, I did'nt ride the bike very long but I kept it around to keep an eye on it and after a year or so there was more spider veins and out right rust than I was comfortable with, the coater that I use does mostly medical equipment so I dont know if they did something wrong or not but I imagine that the same thing would be going on with colored coating. My guess with paint is that a coat of metal etch and then a good primer under the paint goes a long way towards keeping the bike healthy.

I have had both methods done on bikes since that bike and every time I see a new nick in powdercoating I think back to the clear bike.

I would second what Allan and Peter have said. Being a painter too, proper prep for either paint or powder is about 90% of the work, shooting the coating is a fraction of the time. Like paint, there are a lot of different kinds of powder and some work better for inside applications, and some better for outdoors. I've seen rust grow under powder too, but in those cases, it's generally been because the powder was put on in too thin of a coat. Economics obviously come into play, but when the powder is put ojn thin, especially in only one coat, apparently microscopic holes between the grains allow easy ingress of moisture straight to the base metal. For chips and scratches right to the metal, any coating will allow rust to start forming. I do like the powder coats for their improved toughness, but the coating has to be applied properly.

Wow. Thank you for all your advice guys. Now I'm not really sure what to do. I think I'll cover up the nicks in the original paint and keep the original for as long as possible.

Ok, so I want to strip down one of my frames and get it painted.

I can get it powder coated, or I can get it sprayed up at an autobody shop.

Which is going to be more durable? This is for an every day/bad weather commuter bike, so it's gotta be a pretty tough finish. Esthetics come far secondary to durability.

So what say you?
Which is more durable? Auto paint, or powdercoat?

Neither. Use a two part resin paint. Car restorers use them to chip proof underbodies - they're that tough. The most rust proof is probably Epoxy Mastic, a Norwegian product developed for the oil industry. You don't get much of a colour choice, but it is tough! (It's what I've decided to use on my bike come the autumn.)

See http://www.rust.co.uk/epoxy-mastic.cfm

Oh - and you can put it on with a brush and won't get marks.

I've lost the URL for this - it's from the CTC website - but it's superb. It's for really rusty frames but still useful in general, if a little OTT:

by MikewsMITH2 » Sat Jul 25, 2009 9:25 am

I'm afraid paint won't stop rust coming through, to prevent this the rust needs to be neutralised first. This is what you need to do:

1. Strip back to bare metal using Nitromors paint stripper.
2. Sand down until all surface rust is removed.
3. There will still be rust in the pits - sometimes so small you can't see it. To neutralise this you need to use phosphoric acid. This is available in gel form from Halfords and the like as "Hammerite rust remover". This is a very weak form and will work but you may need several 2-3 hour application cycles before all the rust turns to a blueish colour. The best stuff to use is "Jenolite" from jenolite.com or "Milkscale remover" from an agricultural merchant. This is stronger and cheap.
When the rust is neutralised use "Hammerite Number 1 rust beater". This is a zinc phosphate rust proof primer.
4. Then prime and paint as normal.

This process has been used in classic car restoration trade for many years and done properly this will definitely kill the rust. I have done two rusty 1960's frames (one very rusty) and used one all last winter with no recurrence of the rust. If there is much rust on the frame it's probably best to get it media blasted, but still use the jenolite/milkscale remover as the blasting process will not remove all the rust in any pitting there may be.

Another tip is to use plenty of paint to make sure moisture cannot get through. A 2 pot epoxy paint is best as this is totally waterproof whereas convential enamles aren't. I also clearcoat the the whole frame after the transfers have been fitted. Plasticote is the correct stuff for this as it won't damage the transfers. I also wax mine with car wax after the paint has hardened. The only problem with professional re-enamelling is to make sure they are using the correct process of blasting/dipping to remove and neutralise any rust. Obviously if your frame isn't rusty then stripping, priming and painting is sufficient.

Just by the by, I don't know of any epoxies that are completely waterproof. They will all (?) eventually pass water through in tests that are designed to see how long an equilibrium of moisture takes to establish itself. Of course that may not mater in this application, since steel is not a block of wood in a vapour environment.

I have been told the same positive things about 2 part epoxies, as mentioned above, from various sources, my only concern is whether they are UV strong. Some frames will be stored indoors and see few days of sunlight per year. A bike that sees a lot of light needs to be UV resistant. Epoxies in my experience chalk up and need a top coat of LPU or some such. This is why the epoxy primer and LPU topcoats formula is popular.

Now if anyone know a product that will prime metal for high gloss latex house paint...

You won't find a waterproof epoxy paint at all, and for two good reasons;

1.) There's no such thing as a waterproof plastic. End of.

2.) Epoxy system paints were originally developed to be the primer body for high-durability, extreme service applications, such as aerospace and marine, and by peopel who understood and accepted that all polymers no matter their thickness or chemistry allow water and gas transfer. Almost all aeospace calibre paints are epoxy primer based and that primer is not only porous, but the porosity is intentional. Strontium chromate and zinc-potassium chromate bearing films are laid down on top of aluminium, steels, magnesium and titanium alloys to cathodically protect the substrate but they cannot do that without being electically connected to both the substrate and the interface with the next paint layer.

The intention here is to put a hopefully, mostly waterproof, ish, barrier coat down on the top of this epoxy and once, eventually water has managed to get through it, then the primer/protection can do its job.

This said, epoxy undercoat primers are remarkably durable when properly topcoated. I can recommend Indestructible Paints for any of their systems. They sell mostly to industry, but you can deal with them in small quantities as a private purchasor if you don't mind paying for the best.

Just by the by, I don't know of any epoxies that are completely waterproof. They will all (?) eventually pass water through in tests that are designed to see how long an equilibrium of moisture takes to establish itself. Of course that may not mater in this application, since steel is not a block of wood in a vapour environment.


That's very interesting and very useful - thanks! I shall ask questions of manufacturers etc.



I have been told the same positive things about 2 part epoxies, as mentioned above, from various sources, my only concern is whether they are UV strong.

Por 15 Hardnose is claimed to be extremely UV strong... Now I've checked to Epxoy Mastic that detail seems to have been skipped. Suspicious!

You won't find a waterproof epoxy paint at all, and for two good reasons;

1.) There's no such thing as a waterproof plastic. End of.


Really??? I didn't know that - that's fascinating.



2.) Epoxy system paints were originally developed to be the primer body for high-durability, extreme service applications, such as aerospace and marine, and by peopel who understood and accepted that all polymers no matter their thickness or chemistry allow water and gas transfer. Almost all aeospace calibre paints are epoxy primer based and that primer is not only porous, but the porosity is intentional. Strontium chromate and zinc-potassium chromate bearing films are laid down on top of aluminium, steels, magnesium and titanium alloys to cathodically protect the substrate but they cannot do that without being electically connected to both the substrate and the interface with the next paint layer.


Porosity is a side effect of this? Or is porosity itself the electrical connector, via the flow of ions through it?




The intention here is to put a hopefully, mostly waterproof, ish, barrier coat down on the top of this epoxy and once, eventually water has managed to get through it, then the primer/protection can do its job.


So that would be a zinc(?) primer, epoxy, top coat sandwich???



This said, epoxy undercoat primers are remarkably durable when properly topcoated. I can recommend Indestructible Paints for any of their systems. They sell mostly to industry, but you can deal with them in small quantities as a private purchasor if you don't mind paying for the best.

That's interesting too.

Ok - if someone was painting at home and wanted maximum toughness and ease of use, are there any reasonable options? What about Hammerite? Or Por 15 Hardnose over something like zinc oxide primer? Assuming the Hardnose is UV resistant would the combination be a good one?

I have some bikes I painted in 1980-ish that have been badly abused and have some chips off of the paint. The primer is still holding up. It's amazing.

Really??? I didn't know that - that's fascinating.

Essentially, it's a fundamental of polymer chemistry. Even the most rigid, cross-linked, three-dimensional polymer structure effectively terminates in lots of places rather quickly, so what's left holding these ten-thousand molecular weight monsters together is dipole interactions and Van der Waals forces. Essentially, static. Gas molecules, and tiny liquid molecules can elbow their way through with enough head of pressure. That's why beverage bottles have a shelf life.


Porosity is a side effect of this? Or is porosity itself the electrical connector, via the flow of ions through it?

More... the porosity is capitalised on. The pores allow ion transport and therefore maintain the continuity. The paints are designed to go down in a film thickness range x-y and in that range there can be assumed a surface-connecting porosity range usefull but not excessive.


So that would be a zinc(?) primer, epoxy, top coat sandwich???

That would be.. (etch primer if it needs it), strontium/potassium-zinc epoxy primer, topcoat. Yep.


That's interesting too.

Ok - if someone was painting at home and wanted maximum toughness and ease of use, are there any reasonable options? What about Hammerite? Or Por 15 Hardnose over something like zinc oxide primer? Assuming the Hardnose is UV resistant would the combination be a good one?

You want maximum toughness, I'd say polyurethane topcoat and a good sacrificial epoxy primer. I had to get a Mil Spec PU paint off once. It took a oxy-propane torch and glass bead blasting. No joke. Two HOURS. But it's once again, all down to the prep. You make sure the subsrate is clean and keyed, you take your time with the primer and then you key it again, unless you're handy with putting down a final powder layer on the primer. Be aware that the two are partially mutually exclusive. A wet-coat car paint is real easy to use, but not particularly hardwearing by comparison. A PU paint is a bit of a pig to clean up and strip out of spray tools, but it won't come off, and the chemically resistant nature as a paint is reflected in its behaviour as a film coating.

Essentially, [porosity of epoxy and other plastic paints] is a fundamental of polymer chemistry. Even the most rigid, cross-linked, three-dimensional polymer structure effectively terminates in lots of places rather quickly, so what's left holding these ten-thousand molecular weight monsters together is dipole interactions and Van der Waals forces. Essentially, static. Gas molecules, and tiny liquid molecules can elbow their way through with enough head of pressure. That's why beverage bottles have a shelf life.


Except the last sentence about about beverage bottles, it's easy to imagine Tom Baker giving the above as an explanation of why the Tardis isn't working! But yes, that makes perfect sense.

If you get a moment I'd be interested to know what you think of the info for the site for KBS Rust Stop. They claim that:



http://www.kbs-coatings.com/Rust-Sealer_c_2.html
RustSeal completely seals metal surfaces, blocking all the pores and preventing penetration of moisture, oxygen, and water vapor.


And it's a "Polymeric Isocyanate" according to

http://www.kbs-coatings.com/RustSeal-Technical-Data_ep_45-1.html

I noticed that one of the magazine articles archived on their site claimed that an angle grinder was required to remove this stuff, and even that had problems. It's designed to be used as the middle layer layer of a 3 layer sandwich, btw.



[The best combination would be] would be.. (etch primer if it needs it), strontium/potassium-zinc epoxy primer, topcoat. Yep.

You want maximum toughness, I'd say polyurethane topcoat and a good sacrificial epoxy primer. I had to get a Mil Spec PU paint off once. It took a oxy-propane torch and glass bead blasting. No joke. Two HOURS. But it's once again, all down to the prep. You make sure the subsrate is clean and keyed, you take your time with the primer and then you key it again, unless you're handy with putting down a final powder layer on the primer. Be aware that the two are partially mutually exclusive. A wet-coat car paint is real easy to use, but not particularly hardwearing by comparison. A PU paint is a bit of a pig to clean up and strip out of spray tools, but it won't come off, and the chemically resistant nature as a paint is reflected in its behaviour as a film coating.

Thanks!

If you get a moment I'd be interested to know what you think of the info for the site for KBS Rust Stop. They claim that:

http://www.kbs-coatings.com/Rust-Sealer_c_2.html
RustSeal completely seals metal surfaces, blocking all the pores and preventing penetration of moisture, oxygen, and water vapor.

And it's a "Polymeric Isocyanate" according to

http://www.kbs-coatings.com/RustSeal-Technical-Data_ep_45-1.html

Uh-huh. That means polyurethane. And it's BS. 9 dollars for the protection that RustBullet over here charge 43 quid for? The salesmen are talking. The tech department probably threw a sh*tfit when they saw that.

I'm sure in most cases that their PU coating does block the majority of moisture. But oxygen and water vapour it won't stop, or they'd have tested it in water vapour and listed the results on the page. For reference, just because things like sulphuric acid are listed on there, it doesn't mean very much. All of those materials the coating has been tested in shouldn't affect a protective coating that claims to meet ASTM-B117. All aerospace quality and marine quality coatings must pass ASTM B-117 with flying colours. It's just a normal 5% salt fog test. Hell, we test everything in that, even aluminium.

As for the blocking pores - that's technically true, if you accept 'pores' can mean anything. I think that's the angle they're working.




I noticed that one of the magazine articles archived on their site claimed that an angle grinder was required to remove this stuff, and even that had problems. It's designed to be used as the middle layer layer of a 3 layer sandwich, btw.



That sounds like PU. It just clogs the damned tool.

Uh-huh. That means polyurethane.

I wondered. I checked on wikipedia, but it didn't say anything useful.



All aerospace quality and marine quality coatings must pass ASTM B-117 with flying colours. It's just a normal 5% salt fog test. Hell, we test everything in that, even aluminium.


It it isn't impolite, can I ask who "we" are?



As for the blocking pores - that's technically true, if you accept 'pores' can mean anything. I think that's the angle they're working.

Yes - I wondered what you'd say about that and whether "pores" in steel had some sort of technical meaning I was unaware of or was sheer bs.

This might interest you:



http://www.tfhrc.gov/hnr20/bridge/mastic.htm

On a steel bridge in Central New Jersey used for testing 47 various coating systems, only 3 of the 12 epoxymastic type systems tested graded at 8 or above according to ASTM D610 after eight years of exposure. In the same test, 10 of the 14 systems tested with zinc-rich primers scored 8 or better, and 13 of 14 scored 7 or better.4 (ASTM D610 “8" = 0.1% rust; “7" = 0.3% rust)

In marine exposure testing, epoxymastic coatings from various vendors showed significant underfilm corrosion from intentional defects after as little as 18-months. Similar underfilm corrosion results were found on SSPC SP-5 test panels exposed to laboratory accelerated tests.5, 6

In the FHWA-sponsored “PACE” study, the epoxy primer coating systems tested showed poor performance compared to other generic types of coatings evaluated under similar conditions. This study showed epoxy primer systems failing due to underfilm corrosion.


One thing still puzzles me - why a PU coat on top of the epoxy? My belief is that the zinc is for rust inhibition, the epoxy for toughness, and the PU for UV resistance - but aren't there some epoxies UV resistant now, eg Por 15 Hardnose? Would a layer of this directly over zinc primer work well, do you think?

I wondered. I checked on wikipedia, but it didn't say anything useful.

It it isn't impolite, can I ask who "we" are?

I'm aorry, but I can't tell you, I don't think. The company I work for has military and commercially sensitive clients. It's one of the bigger third-party aerospace companies, though, if you want to do the guesswork ;-)



Yes - I wondered what you'd say about that and whether "pores" in steel had some sort of technical meaning I was unaware of or was sheer bs.

This might interest you:

http://www.tfhrc.gov/hnr20/bridge/mastic.htm

On a steel bridge in Central New Jersey used for testing 47 various coating systems, only 3 of the 12 epoxymastic type systems tested graded at 8 or above according to ASTM D610 after eight years of exposure. In the same test, 10 of the 14 systems tested with zinc-rich primers scored 8 or better, and 13 of 14 scored 7 or better.4 (ASTM D610 “8" = 0.1% rust; “7" = 0.3% rust)

In marine exposure testing, epoxymastic coatings from various vendors showed significant underfilm corrosion from intentional defects after as little as 18-months. Similar underfilm corrosion results were found on SSPC SP-5 test panels exposed to laboratory accelerated tests.

In the FHWA-sponsored “PACE” study, the epoxy primer coating systems tested showed poor performance compared to other generic types of coatings evaluated under similar conditions. This study showed epoxy primer systems failing due to underfilm corrosion.

One thing still puzzles me - why a PU coat on top of the epoxy? My belief is that the zinc is for rust inhibition, the epoxy for toughness, and the PU for UV resistance - but aren't there some epoxies UV resistant now, eg Por 15 Hardnose? Would a layer of this directly over zinc primer work well, do you think?

Nope, nope. Not like that.

The zinc's for the galvanic protection of the underlying steel, yes.

The Epoxy isn't for toughness at all. it's there because it's easy to apply and is porous, so that he zinc can electrically contact the steel, otherwise it'd be worthless. Epoxy isn't particularly tough at all. It's rather brittle, no matter its formulation. What it is is *rigid*.

The PU is for the toughness. Neither PU or epoxy systems without the correct additives are particularly UV resisting. PU especially yellows horrendously (electronics conformal coatings which are essentially pure PUs demsontrate this well) as it crosslinks to terminal brittleness. The additives are what make both UV resistant, but naturally PU starts off tougher and more impermeable. I say *more*, and remind you of that. Neither *are*. So it takes less additive to keep it more tough, if you see what I mean.

Yes, there are a number of UV resistant epoxies, but the aerospace sector tends to throw PU down on top because it's tougher, not more UV resistant.

And yes, you can put an epoxy topcoat down on top of the zinc epoxy primer, although it won't be as damage tolerant as PU.

Hope that helps :-)

The zinc's for the galvanic protection of the underlying steel, yes.

The Epoxy isn't for toughness at all. it's there because it's easy to apply and is porous, so that he zinc can electrically contact the steel, otherwise it'd be worthless. Epoxy isn't particularly tough at all. It's rather brittle, no matter its formulation. What it is is *rigid*.


You've been awfully good - but can I ask you to disambiguate one more thing? In this case are you talking about an epoxy that contains zinc, or epoxy as a second layer over a zinc primer? If as a second layer, surely the zinc is already in contact... so you're talking about an epoxy with zinc in, yes?



The PU is for the toughness. Neither PU or epoxy systems without the correct additives are particularly UV resisting. PU especially yellows horrendously (electronics conformal coatings which are essentially pure PUs demsontrate this well) as it crosslinks to terminal brittleness. The additives are what make both UV resistant, but naturally PU starts off tougher and more impermeable. I say *more*, and remind you of that. Neither *are*. So it takes less additive to keep it more tough, if you see what I mean.


Very clear.



Yes, there are a number of UV resistant epoxies, but the aerospace sector tends to throw PU down on top because it's tougher, not more UV resistant.

And yes, you can put an epoxy topcoat down on top of the zinc epoxy primer, although it won't be as damage tolerant as PU.

Hope that helps :-)

Very clear. Thanks!

In this case are you talking about an epoxy that contains zinc, or epoxy as a second layer over a zinc primer? If as a second layer, surely the zinc is already in contact... so you're talking about an epoxy with zinc in, yes?


The zinc is applied in these cases as a particulate suspended in the primer. In the case of galvanizing or sheradizing, where the zinc is in intimate contact with the iron, a primer can be applied over the top, but that primer only needs to help the paint stick.

In a zinc primer, only a very small amount of the primer is in direct contact with the substrate, and so to make an effective sacrificial coating for years of service, that zinc needs to remain in electrical contact by ion flow, but also..
Whoops, I knew I'd forgotten to mention something...

As the zinc corrodes preferentially to the substrate, it reacts with oxygen and carbon dioxide to form zinc oxide and carbonate, which takes up more space than the zinc itself, filling those pores gradually, making the coating self-healing. The pores only seal shut once all the zinc in that interlinked pore space has reacted, so there's a minor second advantage/use of the porosity of paints

Anyways, yes. I'm on about zinc in primers :-)

Holy crap a lot of stuff happened in this thread while I was away!!!

Ok, so powdercoat is porous. But here's a question for you. I have a fair amount of experience with firearms. Several of the finishes used on firearms are porous, such as parkerizing. Now I know that people recommend that you take a parkerized gun, and wipe it down with oil on a silicone rag because the oil is absorbed into the pours of the finish and makes the gun more impervious to the elements. Is that possible, practical, or helpful on something like powdercoating to help protect the metal underneath?

Ok, so powdercoat is porous.

My 2 cents is to spray automotive type clear over the powdercoating.

All you have to do is wipe the frame with DX330 Wax & Grease Remover and spray!

Shiny, like paint; durable, like powdercoating! :thumb:

"Is that possible, practical, or helpful on something like powdercoating to help protect the metal underneath? "

Don't know, the stuff in parkering almost soaks up the oil. It's not that powdercoating sucks, it's just that if a person is specifically looking for something to waterproof their tubes, I am not sure powdercoat is the super star. And all these finishes scratch up easily enough. I Like PC because a local guy will do a frame for 50-60 dollars, and it is pretty eyecatching when he is done. I don't get that from the paint guys. So it is cheap and cheerful, I just don't have any illusions about it being perfect.

Well, it costs me about £45, and I have to assume over the pond the pound sign equates to a dollar one, 'cause that's usually how it is for costs, to strip and respray a frame top to bottom, including two coats of primer, three of colour and three of clearcoat. It's a two day job and the ones I've done so far look awesome...

Holy crap a lot of stuff happened in this thread while I was away!!!

Yes!



Ok, so powdercoat is porous.


I think the real truth is that almost(?) everything is *somewhat* porous. Different quality powdercoats provide different degrees of protection:





http://www.pfonline.com/articles/clinics/1202cl_pwd5.html

Answer: Rusting on steel can be tested in the laboratory using a salt spray test (ASTM B117). This accelerated test is used to determine corrosion limits (rusting) of a particular substrate (steel) using a specific pretreatment and coating. Normally, the test product is scribed (scratched to the base metal) before it is put into the salt spray test chamber. Periodically the test part is removed from the chamber and the coating adjacent to the scribe is examined for "creep" (corrosion under the coating)...

· Mild corrosion resistance 250 salt spray hours; requires good cleaning and a single powder coating.
· Good corrosion resistance = 250 to 500 salt spray hours; requires 70 mg/sq ft of iron phosphate and a single powder coating.
· Better corrosion resistance = 500 to 750 salt spray hours; requires 70 mg/sq ft of zinc phosphate and a single powder coating.
· Superior corrosion resistance = 750 to 1,000 salt spray hours; requires 70 mg/sq ft of iron or zinc phosphate and a zinc-rich powder primer or e-coat epoxy primer and a powder topcoat (two coats in total).



Windridge in the UK provide quite a lot of detail on what they do and use a primer (they don't say if it is a zinc one - but I can't see why it would be anything else):

http://www.windridge.co.uk/content.php/410

The research (with associated money and durability testing) has already been done for you; what did the manufacturer put on it at the factory?

Oh - and a nice surprise for me: the bike I just bought is an '88 Kona. At this period Kona were painting with... Imron, an aerospace and military PU paint - exactly what Falanx recommended! This stuff is very nasty to put on (you *must* use a forced air respirator, etc) but it really is as tough as Falanx says. This bike had been used for mountain biking for almost two decades and not cleaned much. Bearings had gone, anodizing and chrome had failed and corrosion of the components started - but the only missing paint was on the chainstay. It has taken on a slight grey tint, but I suspect that's the lacquer rather than the paint. Yellow isn't my favourite colour, but under the circumstances I think I'll keep this paint job intact.

(So if anyone has any ideas how I can de-grey the bike and make the yellow more intense again, please give me a shout.)

However, for no good reason, I suspect a local autobody shop would not do this particularly well

That's the element that always seems to get left out of these discussions.

A bicycle isn't the easiest thing to spray paint because it's made of round tubes that have to be sprayed on all four sides and it has akward places to paint at the seat stay and chain stay joints. It's really easy to either miss places like the chainstay bridge or to initiate runs.

A skillful applicator, of course, won't do that. A guy whose very good at painting cars, however, might not be so great if yours happens to be his first bicycle frame.

The research (with associated money and durability testing) has already been done for you; what did the manufacturer put on it at the factory?


I think that's rather naive. A manufacturer's priority for a paint job is that it sells the bike, doesn't cause warranty problems, and doesn't cost much. Plus in the case of steel (I don't know anything about alu) it will be going on top of galvanization, which changes everything. Your priorities might be quite different - you might be happy paying an extra $50 for a paint job that will last 5 years longer and be unchippable.

Parkerising is nothing more than iron phosphate, the same stuff that you have on the body of an automobile before it's dip galvanized. It doesn't' so much soak up the oil, rather the film thickness is dependant on the final treatment of the steel, because the phosphate grows epitaxially, so the orientation of the metal grains affects the perceived 'length' of the phosphate crystal columns, and so the 'height' of the crystals in the layer, and the irregularities hold the oil.

My only experience with powdercoat was on my recumbent frame I'm doing and the guy ( a powdercoating shop) put 2 coats on and it is THICK and really covered up a lot of hard work and detailing of the lugs and braze joints I spent tons of hours on. As it's a "development" frame I wasn't too concerned...but for the "production" frame I'll have to decide if I want to do powdercoating again.

It would be interesting to get a TIG welded MTB frame parkerized. Might even be sorta fashionable looking.

Hello guys, new to the forum, my name is Jason Langhoff and i am the owner of Deluxe Powder Coating. I think that Powder Coating is far superior to Automotive Paint for this particular application. As long as the Powder Coater knows what he is doing and has a good prep procedure you will have a great finish that is strong, durable, chip resistant and also has UV protection so it will not fade in the sun. Remember that there are also clear coats in a powder coating finish that are stronger than liquid paint; also all powder coats come in different gloss levels, anywhere from 5-150%. I saw in the thread that someone said powder coating is pourus, which it is not at all, it will actually not absorb oils at all, after cured it creates a skin over the metal, a plastic skin, because all powder really is is finely ground plastic. All you have to do to clean something powder coated is a little windex or some soap and water and it will wipe right off. Also someone said epoxy coatings are weak, they are actually the strongest of all powders, they are extremely hard and will withstand the test of time, the only problem with these coatings compared to hybrids and poly's is that they do not have any UV protection so when exposed to the sun they will chalk and discolor, which is why they are usually only used for indoor applications. Please feel free to ask any questions!

My only experience with powdercoat was on my recumbent frame I'm doing and the guy ( a powdercoating shop) put 2 coats on and it is THICK and really covered up a lot of hard work and detailing of the lugs and braze joints I spent tons of hours on. As it's a "development" frame I wasn't too concerned...but for the "production" frame I'll have to decide if I want to do powdercoating again.



I have had alot of customers coming in with this problem and let me assure you that this does not always happen, many powder coating shops run automated lines and they cake this stuff on causing this problem. Most powders should only be sprayed on at 1.5 mils thick, which is very thin, the thickest would be 3.0 mils which is still not thick. Dont give up on PC!! Some of us take our time out there!!

Oh I liked the way it looked, it was however like... "why did I spend all those hours dressing up the joints and lugs if the PC just covered up everything and softened the results. I believe the guy did go around 3 mils.

Hello guys, new to the forum, my name is Jason Langhoff and i am the owner of Deluxe Powder Coating. I think that Powder Coating is far superior to Automotive Paint for this particular application. As long as the Powder Coater knows what he is doing and has a good prep procedure you will have a great finish that is strong, durable, chip resistant and also has UV protection so it will not fade in the sun. Remember that there are also clear coats in a powder coating finish that are stronger than liquid paint; also all powder coats come in different gloss levels, anywhere from 5-150%. I saw in the thread that someone said powder coating is pourus, which it is not at all, it will actually not absorb oils at all, after cured it creates a skin over the metal, a plastic skin, because all powder really is is finely ground plastic. All you have to do to clean something powder coated is a little windex or some soap and water and it will wipe right off. Also someone said epoxy coatings are weak, they are actually the strongest of all powders, they are extremely hard and will withstand the test of time, the only problem with these coatings compared to hybrids and poly's is that they do not have any UV protection so when exposed to the sun they will chalk and discolor, which is why they are usually only used for indoor applications. Please feel free to ask any questions!

When the PC becomes "chalky and discolored" form UV exposure, does it lose any of the protective properties? What I mean to say is, is it more likely to chip, or form micro cracks that would allow water penetration to the metal? Or is it merely cosmetic? I know that the amount of UV exposure is really more of a predictor of durability than time, but can you roughly estimate how long this might take on a bike that is ridden pretty frequently (2-3 times per week for several hours each time) but stored indoors?

The person who said epoxy paints - WET epoxy paints - were 'weak' is in fact a materials engineer working in aerospace applications and routinely deals with paint finishes. Not only was the word 'weak' not used, the word porous was, and that description comes from another man who's worked in epoxy and polyurethane paint technology and research for over forty years.

Second, I'm not quite sure how paints that 'do not have any UV protection' can possibly be 'the strongest of all powders' when by your own admission, they weaken in UV. Chalking and discolouration are responses to chemical damage done by high-energy photons, and if the energy of UV light is all that takes to cause free radical initiation and bond breakdown, then that's hardly very strong. What about bismaleimide or polyester coatings? What about polyimide? In the case of bicycle frames, strength is not an issue. Toughness of the coating is the primary requirement, and that is the reason aerospace puts PU on epoxy. UV resistance has nothing to do with it.

Don't get me wrong, I'm not denigrating your practical understandign and knowledge, I'm just pointing out that some of the contributors to this thread and others aren't just hobbyisits. Some of us have substantial chemistry and materials engineering backgrounds, and have studied, tested, researched and applied these materials themselves to standards much more exacting than the Mil Specs and ASTM standards.

A good powder coat is very, very strong, and tough, but what you have to remember, and I keep reminding people of this because they need it, is that no polymeric barrier coating is impervious to water, no matter how hard you believe it to be so. All polymers, END OF, are porous, by their chemistry. Anyone working with them should know that, understand it and accept it. I've met, in my line of work, a shocking number of people who should and didn't, and then wondered why their polymer film coating, paint, etc was sat on a layer of corrosion products forming on the underlying substrate.

What I've been trying to make people understand is that you must cathodically protect the frame for the longest service life, and powder coating is not usually amenable to zinc or aluminium or magnesium or strontium-rich primers laid down first.

I'm not against PC for applications. I'd just recommend the military approach when it comes to bikes. Sorry...

One of the big things I've learned in this thread and from other research is that a steel bike needs a primer with a sacrificial component - eg zinc. Otherwise a bike can rust underneath what looks like a perfect paint job.

However

1. Don't some powdercoaters offer the option of a steel protecting undercoat?

2. Most bikes today are aluminium. Isn't a powdercoat, even without primer, a more attractive option for them?

Also

3. a distributor for an epoxy paint system just told me that UV damage to his paint only affects appearance and not bonding, scratch resistance, permeability. I'd be interested in Falanx's response.

4. I'm concerned that too high a temperature - or too rapid a change in temperature - during powder coating can make a frame more brittle. Bicycle frame material is funny stuff and I'm not sure that the average powder coater understands the metallurgy here. This discussion is about rims but it still applies:



http://powdercoatingbeginners.blogspot.com/2008/09/powder-coating-wheels.html -

One of the most important things to remember is that metal just simply doesn't like to change temperature fast. While powder coating wheels, it is very important that you slowly and steadily raise the temperature of the part to it's curing temperature, and furthermore, that part needs to come back to ambient temperature very slowly as well too. Quick flashing of heat can make the metal brittle, and can result in powder coated wheels cracking under stress. This is not only very detrimental to your reputation as a powder coating professional, but it is also a big safety concern and potentially deadly. If you found this site while just searching about powder coating, I only hope you read this and take the moment to speak with whoever will be completing your work to make sure proper procedures are followed to insure the structural integrity of your rim. If you merely mention this to them and they laugh and say it will be fine, do yourself a favor and take your work elsewhere. It's not worth risking a harmful situation because some idiots are powder coating wheels and have no clue what they're doing.


If I was going to have a frame powder coated I ***definitely*** wouldn't go with the lowest bidder - you can do an excellent job of protecting a frame with Hammerite or Rustoleum and a brush. I'd only use a powder coater with extensive experience of and a reputation for frame work, who was willing to answer technical questions in fair detail. In fact, I'd probably only really trust a powder coater who works with a custom frame builder, or has a recommendation from one.

And talking of technical information, why does

www.deluxepowdercoating.com/contact.html

...link to a porn site?

I have had alot of customers coming in with this problem and let me assure you that this does not always happen, many powder coating shops run automated lines and they cake this stuff on causing this problem. Most powders should only be sprayed on at 1.5 mils thick, which is very thin, the thickest would be 3.0 mils which is still not thick. Dont give up on PC!! Some of us take our time out there!!

That's the trick, there's a balance between getting coverage on the edges of the lugs without filling in and losing definition.

Question for you on what can be done with PC - I know you guys mask threads and other such, is it possible to mask for things like chrome stays or partly chromed fork legs? The junction doesn't need to be perfect - that's what pinstriping and lug lining is for, but does need to be fairly clean.

However

1. Don't some powdercoaters offer the option of a steel protecting undercoat?

2. Most bikes today are aluminium. Isn't a powdercoat, even without primer, a more attractive option for them?

3. a distributor for an epoxy paint system just told me that UV damage to his paint only affects appearance and not bonding, scratch resistance, permeability.

4. I'm concerned that too high a temperature - or too rapid a change in temperature - during powder coating can make a frame more brittle. Bicycle frame material is funny stuff and I'm not sure that the average powder coater understands the metallurgy here. This discussion is about rims but it still applies:

http://powdercoatingbeginners.blogsp...ng-wheels.html -

One of the most important things to remember is that metal just simply doesn't like to change temperature fast. While powder coating wheels, it is very important that you slowly and steadily raise the temperature of the part to it's curing temperature, and furthermore, that part needs to come back to ambient temperature very slowly as well too. Quick flashing of heat can make the metal brittle, and can result in powder coated wheels cracking under stress. This is not only very detrimental to your reputation as a powder coating professional, but it is also a big safety concern and potentially deadly. If you found this site while just searching about powder coating, I only hope you read this and take the moment to speak with whoever will be completing your work to make sure proper procedures are followed to insure the structural integrity of your rim. If you merely mention this to them and they laugh and say it will be fine, do yourself a favor and take your work elsewhere. It's not worth risking a harmful situation because some idiots are powder coating wheels and have no clue what they're doing.

www.deluxepowdercoating.com/contact.html (http://www.deluxepowdercoating.com/contact.html)

...link to a porn site?

1.) I'd hope so, and if they do, then I'd be very happy with their work.

2.) Aluminium just cries out to be polished and conversion coated not painted! Also, aluminium cries out not to be welded into structures subject to fatigue, but, meh...

3.) If I had a penny for every time I met a distributor who didn't understand the product or the science... I will say just one thing: Reynolds.

4.) This is mostly nonsense. Metals are *renowned* for their thermal conductivity, even the poorest of the lot, such as austenitic stainless steels are orders of magnitude better than paints, pigments and polymers. The powder coating materials will crack yes, especially on such high thermal expansion materials as aluminium (epoxy itself is much worse. Aluminium has a Coefficient of Thermal Expansion of 22 ppm, and epoxy-glass composite - restrained by the glass with a CTE of 12 is well over 50, so you can imagine what an epoxy paint base is like. Polyester isn't any better, nor is polyimide, really), but don't go blaming that on your substrate.

The range of temperature a powder coat goes through will not, I repeat *not* make metals used for bicycle frames or components brittle. If anything, it will anneal them or temper them and make them less brittle than before. I think he's confusing a loss of strength with a loss of toughness. A cast aluminium alloy car wheel that has been PC'ed and essentially quenched will crack, but not because it's embrittled. It'll crack because castings are full of defects that raise stresses to a point past the newly annealed material's yield point and it deforms, twisting the wheel until a casting defect cracks it. *Not* the same thing.

The only clown in this context, Meanwhile, is the fool who's put that PC blog up.

Also:

Hmm... Yes, that link worries me.

Sorry if I sound irate.

1.) I'd hope so, and if they do, then I'd be very happy with their work.

We're both in the UK; you might want to contact Windridge Powdercoaters and ask what their primer layer is.



2.) Aluminium just cries out to be polished and conversion coated not painted! Also, aluminium cries out not to be welded into structures subject to fatigue, but, meh...


Yes, well, let's not think about handlebars, hm? (Seriously - it amazes me that people don't at least inspect alu handlebars and stems on second hand bikes! I'd rather have a brake failure than lose half or all a handlebar - and it does happen.)



3.) If I had a penny for every time I met a distributor who didn't understand the product or the science... I will say just one thing: Reynolds.


???



4.) This is mostly nonsense. Metals are *renowned* for their thermal conductivity, even the poorest of the lot, such as austenitic stainless steels are orders of magnitude better than paints, pigments and polymers. The powder coating materials will crack yes, especially on such high thermal expansion materials as aluminium (epoxy itself is much worse. Aluminium has a Coefficient of Thermal Expansion of 22 ppm, and epoxy-glass composite - restrained by the glass with a CTE of 12 is well over 50, so you can imagine what an epoxy paint base is like. Polyester isn't any better, nor is polyimide, really), but don't go blaming that on your substrate.


That's reassuring.




Hmm... Yes, that link worries me.



Me too. Especially the c**k shots. Call me weird, but when I'm considering entrusting one of my most beloved and personal possessions to someone then I want to know what their technical competence is rather than seeing a picture of their trouser snake. Or someone else's trouser snake. Whatever. I want a well organized business that believes in keeping its customers informed.

Even though Epoxy powders chalk because of UV epxosure does not mean that this type of resin is weak, all powders have there strong points and weak points and that is why there are different types of powders used in different types of applications. Epoxy's are used for indoor applications. They are also used for electrical insulators and protective coatings, and they have a very high resistance to most acids and solvents. Polyester and TGIC powders are what I use most of, they have excellent corrosion resistance, great weatherability and can be layed on thin and cured at low temps and have great flexbility and impact resistance. All I know is that I have stripped many bicycles down that have been painted and when I get them down to bare metal they are rusted to high hell, when I strip bicycles down that have been powder coated they seem to look pretty darn clean, thats not science thats just old fashion blue color worker facts. Regardless of being porous or not im positive that water gets in your frame in many more ways than finding its way through the paint or powder. When I prep the part to powder coat, it is complete bare metal, i pretreat with a phosphate coat and rust inhibators and if you want to pay the extra money for a zinc primer we will do that too. Im not quit familiar with what a military approach means but this is just what I do and I powder coat close to 30 bicycles a week, and people seem to be happy with the results. :twitchy:

That's the trick, there's a balance between getting coverage on the edges of the lugs without filling in and losing definition.

Question for you on what can be done with PC - I know you guys mask threads and other such, is it possible to mask for things like chrome stays or partly chromed fork legs? The junction doesn't need to be perfect - that's what pinstriping and lug lining is for, but does need to be fairly clean.

Yes we do that type of work, it usually cost a little bit more because the time it takes to mask is alot, but I take my time and it comes out pretty darn perfect!:thumb:

My 2 cents is to spray automotive type clear over the powdercoating.

All you have to do is wipe the frame with DX330 Wax & Grease Remover and spray!

Shiny, like paint; durable, like powdercoating! :thumb:
+1

I just got my 1973 fillet brazed Schwinn Super Sport frame back from the painter today.

I had it powdercoated last week, applied the decals myself, then had it wet sprayed with a PPG automotive clear coat by a talented frame painter (D and D in San Lorenzo) who does both powdercoating and spray painting, completing five or six frames per week. He wiped down the powdercoated/decaled frame with PPG DX330 wax and grease remover (which he says softens the surface of the powdercoat to give it "tooth" for the clear coat), then sprayed a light coat of clear, let it dry for 24 hours, wet sanded it, and finally sprayed on another, slightly heavier, clear coat.

He claims this is is the best of both worlds and results in a really tough, superior finish. He also said the guy who had done the powdercoat (essentially a competitor) really knew what he was doing.

Cost (in S.F. bay area):

Powdercoat frame and fork - $125
Spray PPG Automotive Clearcoat - $150
Total - $275

http://i32.photobucket.com/albums/d7/k4drd/Bicycles/1973%20Super%20Sport%20CJ809208/CIMG5596sm.jpg

http://i32.photobucket.com/albums/d7/k4drd/Bicycles/1973%20Super%20Sport%20CJ809208/CIMG5598sm.jpg

One thing one does have to be a little careful about is what a material can do in a certain application vs. what a material can do in the actual stuff they have to put on bikes. There are all kinds of finishes out there, some with amazing properties, that are "never" applied to bikes, both in categories that are applied to bikes, and many that aren't.

The "hybrid" finish, powdercoat for the base with wet-paint trim and decals and then a clear over it is looking very good to me. I'm in the process of painting a frame for the first time and I want to know why it's called painting, 90% of it is sanding. Next one gets powder, then I'll paint the lugs, panels whatever, decal and stripe it and then shoot clear. Let the powder coat and the guy doing it create the base and just build on it.