Rust Under Powder Coat

[Clockwork]

I recently took the powder coat off a 1 year old frame and found this corrosion.

Has anybody seen this type of corrosion? Would a zinc rich primer prevent it?

Thanks, Joel

[Mark Walberg]

Not a painter here, except for rattle cans.
Just curious, how dis your get the powder coat off without disturbing the rust lines?
I don't know any way to do that.

[Mark Walberg]

I usually ride my own frames for several months with no paint before powder coating to make sure I like the ride. They get pretty rusty during that time. I have to oil the from between rides to cut down on the rust. They seem to do OK after painting. Haven't seen any rust bubbles percolating up.

[Clockwork]

The powder coat looked pristine on the outside. You wouldn't know these lines are there unless you removed the powder. You can't even feel them with your fingers.

Powder was removed with Aircraft Remover.

[dsaul]

I have seen that on several forum threads about clear powder over bare steel. That rust spidering seems to be something that just happens over time and why clear over bare steel is not recommended.

[Rody]

Joel,

I've been preaching this for years and there are many threads showing advanced oxidation between the substrate and powder layers. Powder is a great finish for aluminum frames, and for steel frames, when used with a powder primer. Powder coating creates no chemical bond between the substrate and the finished product. This allows for a microscopic layer between the two, advancing oxidation and subsequent corrosion. Powder coat is literally nice saran wrap enclosing your frame.

Rody

[Rody]

Here ya go...

Groovy Cycleworks 33-988-537: Raw finishes and a seasons worth of racing...

[Clockwork]

Joel,

I've been preaching this for years and there are many threads showing advanced oxidation between the substrate and powder layers. Powder is a great finish for aluminum frames, and for steel frames, when used with a powder primer. Powder coating creates no chemical bond between the substrate and the finished product. This allows for a microscopic layer between the two, advancing oxidation and subsequent corrosion. Powder coat is literally nice saran wrap enclosing your frame.

Rody

Thanks, Rody. Do you know if an iron phosphate bath before powder helps with adhesion?

[Clockwork]

I have seen that on several forum threads about clear powder over bare steel. That rust spidering seems to be something that just happens over time and why clear over bare steel is not recommended.

This was an opaque powder but seems to have the same issue as clear powder.

[Rody]

Joel,

Adhesion is not the issue as powder does not mechanically bond with the substrate. Clear or opaque, it's all the same.

Using a chemically bonding powdered primer is the solution, though learning cure times for thin tubing for multiple coats takes effort, as subsequent layers are prone to delamination if baked too long or too hot.

Rody

[Tman]

On our bare metal for hot rods, customs and out Bonneville bound cars I use Gibbs Brand protectant. I have seen that rust veining before. With Gibbs you can coat the metal and then paint or powdercoat over it with no issues.

[Will Neide]

On our bare metal for hot rods, customs and out Bonneville bound cars I use Gibbs Brand protectant. I have seen that rust veining before. With Gibbs you can coat the metal and then paint or powdercoat over it with no issues.

Isn't Gibbs a lubricant?

[Tman]

Isn't Gibbs a lubricant?

That is one of its uses, I have never used it that way before.
Gibbs Brand penetrant

[halekai]

I recently took the powder coat off a 1 year old frame and found this corrosion.

Has anybody seen this type of corrosion? Would a zinc rich primer prevent it?

Thanks, Joel

Joel,

I have a Bianchi c. '81 that has that going on all over it. It is a strange finish that I have never seen on another bike...kind of a metallic green clearcoat. I found it with its campy group minus the wheels in a dumpster in SF (don't ask me what I was doing in the dumpster!)

99% of my frames get gun blued using Van's gun bluing solution then I either oil them up (my personal stuff) or I get them powder coated with a high gloss clear, no primer.

I have frames out there from 8 years ago with no issues. It could be the bluing/prep that I do and it could be the powder process that my guy uses. (He does some things differently than others such as 'pre-bake' prior to powder. He also says he uses a premium quality product that others may not. It is the same guy that Cysip uses and I have never heard of this problem locally.

There is a learning curve with the Van's but I wrote an article years ago explaining my method. I'd be happy to forward that to you if you like. It might be worth some experimentation.

[Tman]

Hale, i would like your blueing article

[vib]

Joel,

I have a Bianchi c. '81 that has that going on all over it. It is a strange finish that I have never seen on another bike...kind of a metallic green clearcoat. I found it with its campy group minus the wheels in a dumpster in SF (don't ask me what I was doing in the dumpster!)

99% of my frames get gun blued using Van's gun bluing solution then I either oil them up (my personal stuff) or I get them powder coated with a high gloss clear, no primer.

I have frames out there from 8 years ago with no issues. It could be the bluing/prep that I do and it could be the powder process that my guy uses. (He does some things differently than others such as 'pre-bake' prior to powder. He also says he uses a premium quality product that others may not. It is the same guy that Cysip uses and I have never heard of this problem locally.

There is a learning curve with the Van's but I wrote an article years ago explaining my method. I'd be happy to forward that to you if you like. It might be worth some experimentation.

Interesting
I would be interested too
Do you have pictures of the result?

Thanks

[halekai]

This is the process as explained to Brad of Capricorn Bicycles. It has been refined over the last 5 years in order to save time, energy and product. In the biz this is called “reification”. There is a guy in SF who does this for a living and I am told that he can get all kinds of exotic patinas using exotic chemicals. Hat tip to Ezra Caldwell of FastBoy who inspired me to do this in the first place. His work and saga inspired me to quit medicine and start building but that is another story. I never conversed with him but I suspect that he used a different product than I use as he attained some very dark charcoal like finishes whereas I am getting a deep bronze. Thank-you Ezra…

There are two types of gun bluing or 'Parkerization', Hot and Cold. Hot bluing is a little more involved and involves heat in some way...bottom line is the patina is about 5-10 times thicker than Cold bluing. Go on YouTube and look up some vids of gun guys doing their thing. Cold bluing is done with an over the counter solution (Used to be done with urine from a pregnant human or horse! In a bind I suppose you could still get away with that but...). I have used two different brands. "Perma-Blue by Birchwood-Casey and Van's Gun Bluing. The first gives you a grey-green-olive kind of finish...much lighter than the Van's which is my preferred product. The more applications of Van's the darker it gets until it is almost black. There are a few tricks to it to get it to come out nice and even without blotches and drips...Here is how I do it.

Step one is prep the frame by sanding and getting the brass where you want it. Get the finish polished pretty fine with fine clean emory cloth. no sanding along length of tube, only perpendicular to the length of tube as you will see these longitudinal scratches after finishing! Take a clean t-shirt and "slap rag" the frame to remove all the dust and particles. Wear some thick blue gloves because the stuff will get all over your fingers and make them black for weeks. Ask me how I know that... Get an old toothbrush and apply a little to the toothbrush. Some people use a cloth here but I think the monofilament is neutral and doesn’t wast the product as much. I decant a few tablespoons into an old water bottle with a hole punched in the cap to squirt it on so I dont waste any. (for one bike the small 2oz. bottle is way more than you will need…I use about 4-5 tablespoons). Decant the solution into the water bottle a little at a time. You will see that as the solution comes in contact with the brush or atmosphere its reaction gets used up a little. So you do not want to contaminate the solution in the container. When you apply it you will see that the reaction is robust at first and then stalls. The solution has been used up so you have to keep re-applying it to the toothbrush then bike in small amounts. There does not seem to be a correlation between amount you squirt onto the brush and its overall effectiveness so work on applying it in as little amounts as possible. Work in small areas with the tube horizontal so that drips dont run down the frame. work in the solution with the brush vigorously. After you are done with a tube move on to the next tube around the bike but keep going back and re-wetting the old tubes with new solution a few times during each "coat". continue until you have touched all the tubes at least two or three times this way which will amount to one "coat".

I used to wait until it was all dry and polish the tubes with dry steel wool 0000. Once it is all dry polishing it becomes harder...you will see. Now I do the polishing with a little solution still in place. You will see that there will be areas that get blotchy. These areas must be lightly resanded using wet auto paper at 800+ grit then re-apply solution. The steel wool can get some of it but not the heavy blotches. Don't breath the dust, it is probably nasty.

The brass itself can go two ways. You can leave the silvery-grey-pink patina that piles up or get in there and Hi-polish them to a brighter finish. I have done it both ways.

You will probably want to put at least 3 coats on in this manner. Some brands of tubes react differently to the chemical process. Also the absolutley stunning peacock blues that you get at first application will not last more than an hour or so...sad because those colors are mind warpingly beautiful...if only there was a way...(there is but it involves blasting the frame with a clean flame such as propane until the steel gets a rainbow color much like the exhaust pipes of motorcycles)

Don’t be tempted to leave it on wet overnight to darken up. The wet solution will drip to the low spot and cause a streak of rusting-like corrosion.

After it is as dark as you want it and as polished as you want it take a clean rag (remember that new tshirts and cotton has Lanolin Oil in the fabric so make sure the cotton rag has seen plenty of washings in the past or you will get the lanolin on the frame and the bluing and or powder will not stick) and dry it all off and go over it one last time with a dry piece of 0000 steel wool. Last step is to slap rag the whole frame to get the dust off.

From here you can do one of two things. You can grab some oil, slather it on and call it a day…or you could have it powder coated. I have done both. My personal machines get oiled. I used to use extra virgin olive oil. I am not sure why but it is Very Important to use the extra virgin and not some third rate third press product. Just kidding, use what you want. I started out using olive oil because I am an organic new age kind of guy. I found it to be very high maintenance so I sold out on several levels...dont worry, I was able to justify it! Now I use Marvel Mystery Oil. MMM leaves a beautiful finish and protects the frame for a longer period. Plus it smells kind of minty. I oil my frames 2x a year…more often if they see increased use or if I ride through rain or a puddle. It is a big commitment to this type of finish. I have not tried stripping with solvent and then powdering the frame after oil but I bet there will be issues. Once in a while I’ll get some pitting. In that case I wet sand, re-apply and blend it in with steel wool then re-oil. No big deal.

In the case of powder coating, I bring my frames to AJ at West Coast Powder in South San Francisco. He knows what he is doing.

What I would do is take a sample, gun blue it and bring it to your local guy and ask him to powder coat it using hi-gloss clear. ask him to heat up the tube for a bit over 300*F to burn off any volitiles from the process. This is one of the secrets AJ has told me he does. Then pick it up and do a ding test on the tube. I would rather have it thick than thin.

Another trick I do is to face the BB and HT prior (prior to even doing the bluing process since you will use grease/oil on the frame) and then press/install the bearings without cutting the finish layer. Just let it compress. This offers a little extra protection against creeping rust later on. Be sure to chamfer the outer edge just a little so it is not sharp.

Stainless will not pick up the stain but sometimes there is some blotching so youll have to polish stainless carefully afterward.

One other thing. In the past I have hermetically sealed various tubes instead of putting in weep holes. Most of the time there is no problem but twice I have had micro pin holes in the brazing where the expanding hot gasses leaked and bubbled the powder coat finish. I had to re-do them and it was such a pain in the ass that I just put weep holes in everything and use Tube-Seal from Aircraft Spruce afterward to rust proof everything (way cheaper than framesaver. They use it in aircraft 4130 construction and so it is probably as good a product as anything out there).

I hope that was sufficient. If you have any questions at all regarding this process dont hesitate to ask. Good Luck,

[halekai]

Here is an oiled version of the Berkshire Casey solution...

Flickr

And the Van's with a clear coat...

Flickr

[e.Gellie]

That's great info; thanks for sharing the photo. Quick answer; find a powdercoater familiar with primer. e-coat, phosphate or zinc-phosphate.

I'll add my 2 cents (paste edited bits of what I put up on Framebuilders on Facebook a week ago regarding clear powdercoat.

Primer is used for a reason. A "perfect" coating might seem like a good idea, as was referenced above in a comment. However, nothing is ever so straight-forward; in engineering, the root-cause of snail-trail would be the process of "differential-aeration". When one part of a reactive metal exposed to the oxygen in the air, and the rest of the surface is not, that introduces a galvanic corrosion process, so the corrosion at a scratch is accelerated by a galvanic reaction. Scratch your perfect coating and the corrosion begins, and the snail-trails result. Ugly looking and they occur even with "proper" application of powdercoat clear, as I have observed. (On Facebook some insisted snailtrails can be prevented by "proper application" of some super-dooper clear powdercoat. IMO, no. They sound like product-promotion words to me. It might, at best, slow the corrosion process. What is needed is zinc, sacrificial anode ... .

Wet-paint primer is zinc-rich and is intended to act as a sacrificial anode. Scratch thru to steel, and the steel corrodes less. The zinc corrodes in preference to the steel all-over. Same for galvanised metal products which get a heavier coat of zinc. On big steel structures, they bolt on a hunk of zinc or similar. Hot-water systems have a sacrificial anode that gets consumed over time to delay failure of the tank.

Automotive now seem to use "e-coat" which as best I can work out translating the marketing-speak online, is at its most basic a "phosphate", which would be more accurately described as "zinc-phosphate". I know of powdercoaters who had to do phosphate in order to secure automotive work. When I search for powdercoaters online with the term "primer", some have referred to that.

A frame may never fail from snail-trail corrosion .... or it might if it's aggressive. In my opinion, it's better to find a powdercoater who understands why some powdercoat need a primer, and is set up to do it.

Some of the clear-coated frames from taiwan MAY have been applied over a thin primer of some sort. That sort of info is hard to come by. I wouldn't be in a hurry to do it, because I'd be willing to bet that the amount of zinc or similar applied would be many times less than applied in a good wet-paint primer.

This info is based on my mechanical engineering knowledge and as a full-time framebuilder.

[mahall]

I recently took the powder coat off a 1 year old frame and found this corrosion.

Has anybody seen this type of corrosion? Would a zinc rich primer prevent it?

Thanks, Joel

Joel,
Yep, I saw that and worse on one of my powder coated frames stripped recently. It's an unfortunate reality with powder coating. Wet paint with a quality primer forms a chemical bond with the metal in addition to passivating the steel against corrosion whereas powder coating is just a mechanical bond like a tool dip. Thats a little harsh but it's a good way to visualize what's happening. This of course should not eliminate powder coating from ever being considered but rather should inspire a thought process about what type of paint system is adequate for a particular rider, frame, and climate. Budget constraints of course play into that process. I've worked with three powder coating companies and all have said it's hard to prevent corrosion under the coating. One said the so called powder coat primers and metal treatments will eventually lead to pealing. I'll need more data to accept that one. Anyway, work closely with your powder coaters to instill the following to reduce the chances of corrosion forming behind the coating.

Blast with a clean 60-80 grit media. 100 might work in a pinch too. The pictures of your frame look like it was blasted with too fine of a media, bead blasted, or maybe not blasted at all.

Coat the frame within 30 minutes of being blasted.

After blast don't handle the frame with bare hands.

Never coat the frame when there's evidence of water spots or condensation.

Regards,
Mark