this was brought up in the SS/FG forum, and I wanted to post it here, as you guys will KNOW,....read on if you will:
I was going to get my track frame powder coated but someone told me that it weakens the metal. Does anyone know anything about this? Is that true?
if you take a piece of raw steel and bend it, it'll make a 90 degree bend easily
and it'll hold that shape, now take that same piece of steel and heat it till it's red hot (750+degrees) and then quench it in cold water,......now try and bend it,.....more than likely it'll snap into two pieces, because the heat/quench has created martinzeiss steel(forgive if I spelled it wrong), NOW,...take that SAME piece of steel and heat it gently to about 450-500 degrees (close to powdercoat temprature) and then let it cool slowly (no quench), NOW try and bend it, and you'll find that it bends, but will snap back like a spring.
so I guess the real question here is:
will the heating and slow cooling of the powdercoat process RE-TEMPER the steel? or will it SOFTEN (anneal) the steel?
(I SERIOUSLY doubt you could remove significant amounts of metal by blasting, unless it's soft aluminum, and you are using carbide as the media, which will never happen in the real world, so that point is moot IMO)
and this needs to be answered by a metalurgist, or a machinist with good metalurgy knowledge, or a frame builder, and NOT by a powdercoater (no offense to any powdercoaters out there) as I personally would like a qualified answer simply because of all the internet MYTHS out there.
someone please answer this, and put this to rest.
Dr.Deltron
02-25-08, 09:48 AM
someone please answer this, and put this to rest.
It's OK to powdercoat a steel bike frame!
If it were problematic, big companies wouldn't do it. Check your LBS and see how many hi-end bikes you can find that ARE powdercoated.
Granted, some will be powdercoat with decals on top. Others are powdered, decaled, then cleared with automotive quality clear. There are even a few that have PC color, heat resistant decals and PC clear.
*note* I'm NOT a certified metalurgist, just been finishing & re-finishing BICYCLE frames for more than 3 decades. I've seen it all, as they say.
j0e_bik3
02-25-08, 10:09 AM
It's OK to powdercoat a steel bike frame!
If it were problematic, big companies wouldn't do it. Check your LBS and see how many hi-end bikes you can find that ARE powdercoated.
Granted, some will be powdercoat with decals on top. Others are powdered, decaled, then cleared with automotive quality clear. There are even a few that have PC color, heat resistant decals and PC clear.
*note* I'm NOT a certified metalurgist, just been finishing & re-finishing BICYCLE frames for more than 3 decades. I've seen it all, as they say.
thanks doc,....I appreciate the answer,.......and yes you and I have been painting stuff longer than most of these folks have been alive,....and I know powdercoating won't significantly weaken a steel frame, but I see SO MANY THREADS where people bring this up,.....but it never really gets a "qualified answer", which is why I posted this,.....
so I'd still like to hear what the metalurgists/framebuilders say......:D
and the question still remains unanswered: does the powdercoat process RE-TEMPER the steel or does it ANNEAL the steel?
Dr.Deltron
02-26-08, 09:43 AM
NOW,...take that SAME piece of steel and heat it gently to about 450-500 degrees (close to powdercoat temprature).
From what I've learned over the years is, some powdercoats bake at UP to 425* F.
Some bake as low as 175* F.
Most are baked at 350*-400*F, so I don't think it affects the steel much, if at all. Powdercoating isn't quenched, so I would bet if anything, it would re-temper, rather than anneal, the frame.
But again, I don't think the temps are high enough to do either.
Maybe Mark @ Spectrum Powderworks will see this thread and add his experienced 2 cents! ;)
Oops! Just reread the OP. You DIDN"T want a powdercoaters answer. :p
I base my analysis on the concept that the "Big Boys" wouldn't PC if there was potential for problems. :rolleyes:
j0e_bik3
02-26-08, 05:19 PM
From what I've learned over the years is, some powdercoats bake at UP to 425* F.
Some bake as low as 175* F.
Most are baked at 350*-400*F, so I don't think it affects the steel much, if at all. Powdercoating isn't quenched, so I would bet if anything, it would re-temper, rather than anneal, the frame.
But again, I don't think the temps are high enough to do either.
Maybe Mark @ Spectrum Powderworks will see this thread and add his experienced 2 cents! ;)
Oops! Just reread the OP. You DIDN"T want a powdercoaters answer. :p
I base my analysis on the concept that the "Big Boys" wouldn't PC if there was potential for problems. :rolleyes:
I'm 99% certain your right,...
but it would be nice to have the thread, JUST so I could copy and paste it whenever this question came up :D (which is alot lately)
Nessism
02-27-08, 07:21 AM
There is a metallurgist around here, Falanx, ...somewhere. If you want a definitive scientific answer, it wouldn't hurt to know the exact type of tubing you have and the exact process the powder coat guy is going to use.
Short answer, from a lowly mechanical engineer, is that the powder coat baking won't make enough metallurgical changes to the metal to matter - the temp is too low; process anneal typically involves raising the temp to 900+F and holding for an hour or so and I don't believe any meaningful tempering can occur at powder coat temps and duration.
tool boy
02-27-08, 07:41 AM
"Most heat treated steels tend to anneal, or soften, when heated between about 1000°F and 1500°F."
That comes directly from Henry James. http://www.henryjames.com/oxplat.html
There is no doubt that you have to know what kind of metal you are dealing with as there are hundreds of tube types out there. It is my opinion that powdercoating has been done for so long, on so many different kinds of metals with no issues, that this is a silly question to keep bringing up.
j0e_bik3
02-27-08, 09:43 AM
"Most heat treated steels tend to anneal, or soften, when heated between about 1000°F and 1500°F."
That comes directly from Henry James. http://www.henryjames.com/oxplat.html
There is no doubt that you have to know what kind of metal you are dealing with as there are hundreds of tube types out there. It is my opinion that powdercoating has been done for so long, on so many different kinds of metals with no issues, that this is a silly question to keep bringing up.
I TOTALLY agree,...which is WHY I want a qualified answer (and I believe we now do) so I can refer to it, or paste the answer,...to finally put this to rest.
see?
Cassave
02-27-08, 09:55 AM
Go here http://www.hghouston.com/mtechart.html
Take a good look. Note that no permanent transformations occur to ferrous metals at
anything less that 1000 F. even in oxidizing atmospheres.
physh
02-28-08, 01:21 PM
I make knives as a hobby so I know a couple of things about steel.
Quick answer: no, powdercoating should not significantly change the properties of the steel so you shouldn't worry. For more detail read on.
The changes all depend on the initial state of the steel (effects are cumulative), the alloy used and also the temperature and amount of time the steel is heated.
Cassave, you should not conclude that no permanent change of steel happens under 1000 F becasue of that chart. (proof of this: take a piece of clean steel, and put it in the oven at 300 degrees. come back an hour later, and the color of the steel will have changed. If it was a spring, it will no longer be as springy.)
It takes as little as 300 degrees to change the properties of steel.
Basically what happens is around 300 and above, the crystalline structure of the steel is changed as you heat it. With steel there is a tradeoff between ductility and brittleness.
When steel heat treated, it is heated to critical temperature, and then quenched. This results in steel that is Very hard, yet brittle. With lower carbon steels like what is used in bikes. The metal will not harden and become very brittle. The steel is then tempered by heating between 300-700 degrees for certain amounts of time untill the desired crystalline structure is reached, and a desirable balance of brittleness/ductility is reached.
Ususally tubing is in it's annealed state, I assume that bike frames are in this state, unless they have been heat trated. Forming the metal will cause the metal to work harden, but if the bike is simply welded togeather, this does not happen.
What happens when you heat the metal in excess of 300 degrees is it becomes less brittle. Heating the steel at low temperatures for a long time has a simmilar effect to heating it at short periods for a long amount of time.
Worst case scenario: the bike frame is heat treated, and powercoating will result in the frame becoming slightly softer. However at the temperatures mentioned 400-500 degrees, the effect will be so subtle, I doubt it has any effect becasue knives are heated a around this temperature, yet they remain very hard. If anything it may relieve stress in the frame from welding. Softer through tempering is not the same as annealing. Over tempering untill the steel becomes very soft is not as soft as steel that has been annealed. (two different crystalline structures)
In order to anneal steel, you must heat to critical temperature (red hot), and let it cool slowly (insulation.)
So from what little I know, It should be safe to heat a bike frame to 500 degrees for several hours.
j0e_bik3
02-28-08, 01:44 PM
I make knives as a hobby so I know a couple of things about steel.
Quick answer: no, powdercoating should not significantly change the properties of the steel so you shouldn't worry. For more detail read on.
The changes all depend on the initial state of the steel (effects are cumulative), the alloy used and also the temperature and amount of time the steel is heated.
Cassave, you should not conclude that no permanent change of steel happens under 1000 F becasue of that chart. (proof of this: take a piece of clean steel, and put it in the oven at 300 degrees. come back an hour later, and the color of the steel will have changed. If it was a spring, it will no longer be as springy.)
It takes as little as 300 degrees to change the properties of steel.
Basically what happens is around 300 and above, the crystalline structure of the steel is changed as you heat it. With steel there is a tradeoff between ductility and brittleness.
When steel heat treated, it is heated to critical temperature, and then quenched. This results in steel that is Very hard, yet brittle. With lower carbon steels like what is used in bikes. The metal will not harden and become very brittle. The steel is then tempered by heating between 300-700 degrees for certain amounts of time untill the desired crystalline structure is reached, and a desirable balance of brittleness/ductility is reached.
Ususally tubing is in it's annealed state, I assume that bike frames are in this state, unless they have been heat trated. Forming the metal will cause the metal to work harden, but if the bike is simply welded togeather, this does not happen.
What happens when you heat the metal in excess of 300 degrees is it becomes less brittle. Heating the steel at low temperatures for a long time has a simmilar effect to heating it at short periods for a long amount of time.
Worst case scenario: the bike frame is heat treated, and powercoating will result in the frame becoming slightly softer. However at the temperatures mentioned 400-500 degrees, the effect will be so subtle, I doubt it has any effect becasue knives are heated a around this temperature, yet they remain very hard. If anything it may relieve stress in the frame from welding. Softer through tempering is not the same as annealing. Over tempering untill the steel becomes very soft is not as soft as steel that has been annealed. (two different crystalline structures)
In order to anneal steel, you must heat to critical temperature (red hot), and let it cool slowly (insulation.)
So from what little I know, It should be safe to heat a bike frame to 500 degrees for several hours.
thank you for that detailed, personal experience answer
roadraccer
02-29-08, 11:00 PM
One other question to this thread since we’re on the subject of powder coating. Can titanium be powder coated without any harm?
Dr.Deltron
03-02-08, 10:50 AM
Can titanium be powder coated without any harm?
Yes! Did a LiteSpeed in red with the stays still ti. Decaled & clear painted over them.
Looks awesome!
The customer is local, so he picked it up before I got pictures. I can stop by his place & take some though. ;)
speedemon
03-02-08, 03:06 PM
Decaled & clear painted over them.
You can paint a clear coat over the powder coat? I didn't know that, I thought of doing that but wasn't sure how good the clear Urethane would bond to the powder coat? I have seen some that written on even powder coating clear over the decals. How would I find out if the Litespeed decals could be cleared over with a layer of powder coat? I'm thinking of having my Litespeed frame powder coated in a coat of color with seat & chain stay remaining in Ti , then decaled, and then fully cleared, or also can I paint the frame with a coat of Urethane color, then decaled and finalize it with a coat of clear powder coat over the top?
Dr.Deltron
03-03-08, 09:45 AM
You can paint a clear coat over the powder coat? I thought of doing that but wasn't sure how good the clear Urethane would bond to the powder coat?
Yes!
Just clean the frame with Wax & Grease Remover thoroughly. Apply decals and spray the clear.
I use PPG's 2042 clear.
It chemically bonds to the powdercoating, no sanding or scuffing needed.
How would I find out if the Litespeed decals could be cleared over with a layer of powder coat?
You could contact LiteSpeed, but my guess is that they are NOT powdercoatable.
At least the ones I used weren't, they were just regular dry transfer decals.
Powdercoat decals are a rare breed. They have to be able to withstand the baking temps of powdercoating.
I'm thinking of having my Litespeed frame powder coated in a coat of color with seat & chain stay remaining in Ti , then decaled, and then fully cleared...
That will look beautiful!!:D
.... or also can I paint the frame with a coat of Urethane color, then decaled and finalize it with a coat of clear powder coat over the top?
NO!
Powdercoating CANNOT go over any type of paint!
Actually, it can, but..........it'll chip more easily than rattle can laquer! :eek:
This little detail from a thread of a few months ago. The poster showed pics of a powdercoat job that apparently WAS done over paint! You could see the paint underneath the pc where it had chipped pretty badly.
Powdercoating does NOT chip if it's done properly. ;)
SOooo...powdercoat the base color. Apply decals. Spray with 2042.
Quick, easy AND beautiful! :)
timo888
07-25-08, 11:44 AM
Small shops may not have access to the technology, but there are UV-cured powders (http://www.dsm.com/en_US/html/dcr/uv_general.htm).
Peterpan1
07-25-08, 05:45 PM
With the average piece of chromo there won't be adverse hardening if it is welded, heated etc. If there was to some fractional degree the 400 degrees would actually help maters by reducing the hardness. I temper tools in the 350 to 400 degree range. The steel, though, has a much higher carbon content to get it to harden in the first place.
bionnaki
08-10-08, 10:44 PM
I have a question: I am interested in getting a frame powdercoated that was already powdercoated previously (I would rather have a different color). The local powdercoater said he could easily remove the powdercoat by dipping it into a chemical bath. Are there any negative consequences to doing this such as the chemicals not being totally removed from inside the tubes and causing future corrosion problems?