View original topic: How to solve this windshield frame problem
Blaubus Wed Apr 14, 2021 11:03 am

I have a 71 bus and the windshield frame has never stopped rusting since I bought it 23 years ago. I have a lot of experience working on the bus and 20 years experience working with paint but i dont see how I will ever be able to solve the problem. I always tell people I will be buried in this bus but I think now I just want to get rid of the whole thing because I cannot solve this chronic issue.

Last time I painted it, I used PPG DP epoxy primer and Concept topcoat, followed all the rules correctly, the windshield seal leaked for about a year, then sealed up on its own for some reason I dont understand. I am sure water infiltration had something to do with the rust but I might have also trapped moisture under the paint. It's bubbled up everywhere. Most of you guys dont know busses but the windshields are difficult to seal up. I have installed hundreds over the last 43 years. They just suck, IMO.

I must be getting desperate because I resorted to using POR 15 on all the rusty areas because sandblasting is out of the question with a car that I intend to keep in service. Blasting would mean a total stripdown and I cannot even rent a place with electric service, unless I want to spend thousands on just this one problem. I really dont even think POR 15 is going to be the end of the story. It seems like I am destined to eventually have to weld in a Gerson lower frame to solve this. And, if that is the case, why even spend any money on paint? I even have the topcoat but it would still take 250+ to buy a quart of DP, reducers, and hardeners that expire in 2 weeks, only to have it leak again and rust again.

Add to this that it is just too cold to paint right now, yet the job has to be done right now- I have to move in 2 weeks. I could use IR curing, just add that to the bill. So the question is: what about the idea of using rattle cans for now and then remove and rattlecan paint properly at a later time when I have the shop space and temperatures. I worry that residue left behind by the rattle can will prevent me from ever being able to use auto paint in the future, since the two types of paint are chemically incompatible. As it is though, I am not even sure auto paint will play well with POR 15. I actually wish the whole lower frame had rusted so I could just POR15 the whole lower frame. Instead, part is smooth metal and part is POR 15. POR 15 wont stick to clean metal, otherwise I would just POR 15 the whole thing and install the window. Perhaps I shouldnt paint at all and just wait for it all to rust that badly so that I no longer have to rely on paint or have the recurring problem. Every idea I can come up with at this point seems insane, either price-and-timewise or wastedbus-wise.

I wish my bus was a shitbox with no redeeming qualities. that way, I could justify not doing this properly. Instead, it's a rustfree CA bus that I painted properly, now turning to shit in this one area.

I wish I could rely on autobody shops to do this. The last two totally fucked up the job in ways that made the paint flake off. One used epoxy primer as sanding primer because they didnt have sanding primer in stock, they just let it harden on the whole bus and then scuffed and topcoated. The other shop used no primer at all!. Different busses, not this one.

Ideas? Is there a rattle can brand that anyone can recommend? Rustoleum seems to dry so slow, is Krylon better?

Mike Fisher Wed Apr 14, 2021 11:49 am

I've heard that silver & black brushed on stops rust.
The silver is satin finish & can be used alone but the black on top makes a nice gloss black paint job.

Blaubus Wed Apr 14, 2021 12:26 pm

I researched the Masterseries and I looked like a better coating than
POR15. I decided against the Masterseries only because it seemed that the POR 15 was easier to acquire locally, within the short timeframe I faced. As you might be able to see in the photo, I already coated the rust- with POR 15.

The real question is: what should I put on the bare metal that wasnt rusty. Both companies make a chassis black. Are you thinking it might be a better way to go than rattle can paint? Does it cure as hard as the POR15 rust preventive coating did?

68IHscout Wed Apr 14, 2021 12:28 pm

“Zero rust” in spray can, rust inhibitive coating, recommended to me by auto paint supply . Use respirator when spraying

marklee Wed Apr 14, 2021 12:45 pm

Once the metalwork is treated, before the glass goes in, give the area a liberal coat of vaseline to keep water away from the metal

Blaubus Wed Apr 14, 2021 3:17 pm

I just talked to a rep at POR15 and they said I can coat the clean metal as well, as long as I prepare the metal to optimize adhesion. So, I plan to coat the entire lower frame with POR15, to prevent leaks from ever rusting it again. I can also scuff up the POR15 and topcoat with automotive paint. This will be a lot cheaper and more effective at stopping rust than using DP.

viiking Wed Apr 14, 2021 5:18 pm

I know it is counterintuitive but you want the clean steel to get some flash rust on it as well.

Why? Because one of the steps that POR15 and most moisture cured polyurethane anti rust paints is to treat the rust with Metal Ready I.e. a phosphoric acid based cleaner. This produces a phosphate coating which is very stable and is the ideal base for subsequent coatings including POR15,MS, Epoxy primer.

If you use POR15 on too clean a metal it tends to increase the possibility of the paint losing adhesion and lifting.

infiniteLoop Wed Apr 14, 2021 6:38 pm

A aspect of treating rust: instead of completely removing it, is that rust is not rust. It can be different thicknesses and the crystal structure can be different. With phosphatizing, if the rust is too thick, the deeper layers will not get converted, and if too thin, all of the rust will get removed. So you have to have a few thousands of an inch with the same crystal structure for it to work perfectly. To do this, you have to remove all of the rust and then deliberately cause it to rust so it can be controlled. With a rust bucket, a rust converter is slapped on and the quality of the job is dictated by the time frame for it to be completed. With a keeper vehicle ,I would remove all of the rust with a wire brush and phosphoric acid treatment. Then, I would use a sacrificial primer with zinc in it.

Blaubus Fri Apr 16, 2021 5:18 am

Quote: To do this, you have to remove all of the rust and then deliberately cause it to rust so it can be controlled.

Exactly what I was thinking. Confirming that for me encourages me to try it. Question is, how long do I let it rust for? I was thinking wet rags for a few week, followed by light wire brushing, cleaning and phosphatizing with their chemicals but is that enough time and rust or will the phosphatizing just remove that little rust??

orwell84 Fri Apr 16, 2021 6:14 am

Sandblasting this area wouldn’t be that hard. You wouldn’t have to strip the bus. With the windshield out, tape it up from the inside with heavy plastic or paper to completely seal the opening. Cover the rest of the bus and the vents. Blast until the rust is gone. Epoxy prime and paint.

I have two bus restoration books written in the UK. At least one of these suggests removing the windshield and seal and checking, cleaning it up. It’s just a rust prone area, partly because of the design though I’m sure the fit of aftermarket windshields and seals doesn’t help. I did mine a few years back and will probably pop out the windshield and have a look at some point.

Busstom Fri Apr 16, 2021 12:43 pm

^^^ Agreed, super easy to spot-blast. Just lay a large tarp over the whole front of the Bus, and tape it into place. Then with a razor, slit open the tarp along the base of the windshield frame, and use a QUALITY! duct tape to close the tarp off to the surrounding areas, leaving the slit area exposed for the sandblasting on the windshield frame.

esde Fri Apr 16, 2021 5:53 pm

sandblast, treat with ospho, and then shoot with epoxy primer. POR15 has too many issues to consider using it under a color topcoat.

viiking Fri Apr 16, 2021 10:00 pm

[quote="Blaubus"] Quote: Question is, how long do I let it rust for? I was thinking wet rags for a few week, followed by light wire brushing, cleaning and phosphatizing with their chemicals but is that enough time and rust or will the phosphatizing just remove that little rust??

Once you have cleaned it back to bare metal it should flash rust reasonably quickly. In days in a humid environment. Yes wet it and leave it and you should start to see that orange-red texture on the steel. I would NOT wire brush it again. The Ospho or rust converter wants that oxidised steel to react with. It is this reaction that binds together the steel and the iron phosphate to give you a perfect basis for the next step. Either use a product like Master Series - perhaps silver which has a higher solids content that will help fill any pinholes or imperfections from the grinding, or use epoxy primer.

Note not all rust converters are phosphoric acid based. Some use Tannic acid but the results are still the same. Just follow the manufacturer's recommendations.

The purpose of any paint is to just exclude oxygen from the steel. If you do that then rust cannot continue. The issue is to make sure the paint you use does that. Note that many primers are completely porous and will not protect. Even some epoxies are porous, but this forum will give you suggested good products to use.

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