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Paint Removal Problems

Old 03-17-10, 05:03 PM
  #1  
stephend
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Paint Removal Problems

Hi all,


I've stripped the paint off an old steel frame using chemicals (nitromors) and although this has taken off 95% of the paint, I've been left with a thin layer of... something. I have no idea what it is but it has come up in some places but not others leaving an uneven finish on the frame.


I first thought I messed up the frame by corroding it with the chemicals or something. But nitromors seems to be a popular choice for this sort of thing and I haven't used too much.

I'm thinking it could be the remains of the primer, or maybe an anti rust paint of some sort.. but it refuses to budge. No amount of paint stripper, sanding, or even a wire brush is removing it. Any ideas what it might be? The frame is mid eighties and has never been stripped down so this paint as been on it for years... I'll try and get a picture up shortly.


Has anyone come across this sort of thing before?!!


Thanks


Stephen
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Old 03-17-10, 05:14 PM
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desconhecido 
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It's hard to say for sure at this distance, but if you can't cut it chemically and it is resistant to abrasion, then it might be some metal artifact of the manufacturing process. Paint/primer isn't that tough.

You don't say what the frame is made from. If it's steel, wash it with wood alcohol to remove all the chemicals that you've used so far. Then, wash it with a metal preparation chemical containing phosphoric acid. You can find such things at Home Depot, etc. then maybe alcohol again or acetone This will give a good surface for painting. Then, because you have an unevenness associated with this thin layer of something, apply a leveling primer. Then either a primer or top coat depending on the paint manufacturer's recommendation. If you have problems with the topcoat smoothness, sand with 400 to 600 wet and dry and re-apply the topcoat.

Make sure to ventilate yourself and protect your skin.
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Old 03-17-10, 05:24 PM
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stephend
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Hi,

Thanks for the advice. Its a steel frame - columbus sl to be exact. I'm not fussy about getting it perfect. I'm just concerned that as I start to put primer and top coats on that the unevenness will show through and it ill become a nonstop circle of sanding and painting. I'll look into leveling primers and will try and build up carefully. I've also considered slandblasting it but I'm hoping to avoid this if I can.


Cheers


Stephen
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Old 03-17-10, 05:55 PM
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desconhecido 
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In my experience, sandblasting should be avoided. First, it gives you a rough surface which can be a pain to level. Second, grains of sand appear as if from outer space when you least want them to be there. It can be a royal pain to get that crap out of every nook and cranny.

Again, if you can't touch the stuff with chemicals or abrasives, it's not likely to be paint or primer or some other prep/sealant/leveler. All those things are chemically susceptible and soft, compared to steel. You're probably looking at some sort of brazing material or metallic filler that the frame maker used to either join things together or to smooth things out.

To get things smooth enough for your top color coat (assuming you're going the paint route) you can use various techniques including spot putty (sometimes called lacquer putty) or some sort of leveling primer. The few frames that I have done have been smooth enough so that spraying with a leveling primer gave a good, smooth surface for the color coats. In any event, whoever finished that frame in the first place finished iit over the same stuff that you are looking at and they did it as quickly and cost-effectively as they could which means that you are likely not looking at something which can't be handled with a little spot putty and leveling primer. The big problem you are likely to encounter is that the stuff you want is normally sold to people who need a gallon or more of paint rather than those of us who need a pint or so to finish a bicycle.
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Old 03-18-10, 04:57 AM
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Thanks for the feedback. I'll give the leveling primer a try. My feeling is that these imperfections were on the frame before I even went near it and the original paint job covered them up nicely. So hopefully I'll be able to do the same with some careful prep. I'll let you know how I get on.


I've attached a picture so you can see exactly what I'm talking about


DSC_0642.jpg



cheers



Stephen
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Old 03-18-10, 05:15 AM
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I'd say it's something that's reacted with the steel during manufacturing.

If you've sanded it and you can't feel it, it shouldn't show through.
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Old 03-18-10, 06:01 AM
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A "real" paint job usually has some sanding of the primer coat just to take care of this type of thing. Part of what a primer does as it's job is to serve as filler. Primer, lightly sand, hit with primer again, scuff, hit with tack cloth and paint.
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Old 03-18-10, 11:02 AM
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It feels pretty smooth by now so I'll try the filler primer and see how I get on.... Thanks everybody!
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