Trunk Monkey

Say I would like to a) modify an existing paint/decal/clearcoat combo and then have the whole frame powder coated over with clear or b) completely strip a frame and add a paint/decal combo. Either scenario would leave a large portion of the frame with a bare steel appearance so a clear coat of some type would be necessary to protect the raw metal. I would prefer a powder coat due to its durability.

I believe typical powder coat curing process are avout 350-400 degrees for around 10 minutes. Does anyone know if a typical decal will survive process in an acceptable manner? I've considered doing a sample and giving it to my local powder coater but if anyone has any experience with it I'd like to know beforehand if it is even worth attempting.

If it means anything the frame is a Soma and I will either be modifying the stock paint job or starting over and using a set of waterslide decals that Soma has provided.

Thanks

mudboy

Powder needs bare metal to adhere to, so what you're wanting to do won't work. You can, however, use normal clear over powdercoat.

unterhausen

There are special high-temp decals for powder, regular decals will just turn brown if not fall off.
Clear over bare metal is a really questionable goal. My observation over the years is that most people report that it looks bad after a relatively short time. There are clear powdercoats that are meant to go over bare steel. I've seen enough unpainted frames over the years to find a bike that looks like an unpainted frame uninteresting. Apparently there are large numbers of people that feel differently.

Cletus has offered to make masked decals. The process is to put down a coat of powder in the decal color, partially cure, mask, and then put down the finish coat.

reddog3

I've not done clear powder coat over bare steel so I can't testify to the result, but I have heard that that it's not really a rust inhibitor. Talk to your powder coat guy about specialty clears for bare steel.

To support Unterhausens conclusions- I did clear coat a bare frame. What was once a shiny cool looking bunch of tubes turned into a dull gray lump of steel. I spent hours with the emery cloth getting just the right brushed pattern on the frame. It had a glint that was really neat. Once the clear went on- it was all gone. The smooth finish of the clear changed how the light reflected. Gray is a good color- just not that shade.

Trunk Monkey

OK so powder over bare steel is a no go. There are acouple of ways I think it MIGHT be doable but timing would be critical and since I'm not the one doing the PC I'll agree that it isn't practical. Good info I appreciate it.

reddog, thanks for the insight. I know exactly what you mean by brushing in a nice pattern. Abrasive, direction, consistency and experimentation are all key in getting a good result. It sucks that you lost that as soon as you applied the finish. Sucks even worse that time made for an unacceptable result. Live and learn... I know you dont have any direct experience with this product but I'm wondering if you think it might have changed things for you:

https://www.imperialrestoration.com/p...php?category=2

I'm thinking the POR-15 might be part of the solution to a sucessful result. POR-15 is known for being very durable a well. Another key would be to eliminate the chance of oxidation. I'm thinking keeping the surface oiled as soon as its gets exposed. A light coat of WD-40 until just before the frame is ready to be cleared and then clean/degrease the crap out of it on what is hopefully a low humidity day.

Did you take any extra steps to protect the steel while you were working on it? How long was it exposed for? Hours, days?

edit: I found the POR-15 link in this post:
https://www.bikeforums.net/showthread...oat+bare+steel

Andrew R Stewart 

Painting is not my area of strength but I have learned a few things. As others have said without a treatment layer over the bare steel it WILL rust quickly. Powder coating isn't chip free. The rust will start at the corners or pressure points, think cable stops or drop outs. Also every painter I've talked with (and I've used 7 over the years) have never advised an oil coat prior to painting. The oil will get into the corners (those corners again) and holes which will not completely be cleaned off, then travel to the surface being painted making adhesion problematic. If you want to protect the raw frame during storage (say the build takes longer then intended or the painting is weeks after completion) consider Navel jelly or some other Phosphate based treatment. This is what Metal Treat is in essence and what a good liquid painter applies before primer is sprayed.

The two part clear, Glisten PC, is interesting. Epically their claim that it gets stronger with moisture. Is there a limit to this? I had thought that some of the wanted qualities of paint was the ability to flex and give a little. Isn't adhesion more important anyway? I don't know much about water based paint systems (if that's what this stuff is, they don't really say) but I always take claims of improving strength without consequences with a grain of salt. Andy.

Falanx

If it's moisture-cured, why is it two-pack?

Paint is one of my specialities and this sounds very much like a acrylic-urethane, the kind that Pro-XL over this side of the pond sells in 200ml cars for the car repair and moddiing garage industry.

I've only seen one single-pack polyurethane that explicitly aims for a moisture cure and that's RustBullet. It's aluminium loaded so it works as a high-resistance barrier anticorrosive, rather than a sacrificial anodic one like a zinc phosphate/chromate ech primer or a high-zinc primers. It works so long as you don't scratch it, more as a paint that corrosion will not start under, unless it's damaged.

POR-15 and other POR products have very conflicting results in the field. Military Fleet tests on them, especially, have found them to be very sensitive to pretreatment and substrate.

Trunk Monkey

I contacted POR-15 directly, conversation below:

Hi,
I have a project in mind and I am unsure what type of topcoat would be best (or if it even exists). Basically I want to do a finish on a bicycle frame that would leave a large portion of it with a bare steel appearance. Obviously I would need some type of top coat to keep the steel from rusting. Would Glisten PC work for such an application? Would any pretreatment of the frame be necessary? Furthermore, would it work as a clear to protect the painted portion of the frame?
I've done quite a bit of searching on the internet and got quite a bit of input (but nothing conclusive) on a bicycle frame building forum. If you would like to add some input based on this topic it can be found here:
https://www.bikeforums.net/showthread...coat?highlight=
Thanks,
"Trunk Monkey"


"Mr Monkey", Our Glisten PC is not a rust preventive coating. I do offer a rust preventive coating in silver. However, it is UV Sensitive and will fade and turn chalky when exposed to sunlight. Our Glisten is an extremely durable clear coat. The tensile strength is 2-3 stronger than automotive clears. I am not aware of any clear coat that will also prevent rust or corrosion and not fade. Thanks, Mike

Michael A. Albrecht
Vice President, Sales
POR-15, Inc.

Falanx

I assume what he means is lap shear strength, but what the hey. That sounds like its an epoxy then. PUs and Acrylics don't chalk, they go yellow if anything.