Removing old black powder coating

Consider sandblasting.

It removes *everything*, but beware... you might find more rust than you bargained for using that method.

I've used black enamel as a replacement paint after sandblasting, and it looks good and is very tough, with a good thick 'gloopy' coating.

We dont' get hammerite here, but the stuff I'm talking about is marketed as a 'steel enamel coating'. Comes in a tin. Applied with a brush. Easy.

Three years later, no rust has shown through. Might be different in the UK with more salt on roads etc. though...

What is the solvent? How quick can you recoat and what happens if you miss that second coat time?

Hammerite is good stuff but you have to be careful applying it with a brush on roughish surfaces. It can form tiny bubbles that are hard to spot, these dry then then burst leaving a tiny pinhole in the coating.

No second coat necessary... it goes on thick and shiny and looks like an enamel plate when finished.

If you really wanted a second coat, I suppose I could have recoated in 4 hours or so, but it's temp. related. It was hot (35 deg C + ) when I used it last.

Solvent is good old turps.

This stuff didn't seem to do that, but then, I'm not that fussy. I just wanted a good waterproof coating, and it looks ok to me- but then it's usually covered in dust or mud anyway.

I've used it on fairly rusty surfaces with no probs, provided you get all the loose flaky s**te off first, it seems to seal up the rust nicely, and stops further corrosion.

I just got the stuff from the local hardware shop. I can't remember the brand name, but it's just an enamel paint designed for steel.

...and of course, you'd try it out on a bit of scrap steel first, of course :)

Was the paint called POR?

Stephen

Where's my sig

with a

That's what Hammerite does, provided you don't get bubbles, in which case you have pinholes that let the damp in...

POR has been mentioned that's a "tractor" paint IIRC. Also good stuff. Hammerite uses (used?) xylene as the solvent.

I can't claim to be fan of Hammerite.

I find it very prone to chipping especially if you can't find a way of keying it to the substrate. It's fine on old rusty stuff but smoother surfaces are a problem.

I've found it OK with a rubbing down with wet/dry. There is a special Hammerite primer for non-ferrous metals.

But the OP asked how to et the original stuff off. Is sand blasting the only way? I did manage to strip some lamp guards by carefully heating the edge of each element then the powder coating would lift off.

The formulae was change a while ago with Hammerite, it is not as good as it used to be, A bit like Evo-stick, that has also gone down hill because they have removed one of the key components probably for health and safety reasons and it has lost its tenacity.

Stephen.

Just noticed, if it is soluble in turps then it wont be POR 15. That is an isocyanate prepolymer which is a petroleum base.

Stephen.

I gave up using it a long time ago (20 years or more, perhaps) - could it now be even worse?

Thanks for the warning about Evo-stick.

In article , hugh writes

...which doesn't work. I tried to use it on the BMW's (bike) starter motor cover, which is an aly casting. it looked dreadful and didn't last at all well. I tried all sorts of approaches: lightly sanding (to key the surface), degreasing with a variety of chemicals, but nothing really made it stick well, and putting Hammerite on top only made getting it all off again much harder.

Basically, don't go there. Also avoid anything claiming to be 'solvent free'. Never mind the head-on assault on English, water-based paints and metals just don't seem suited to each other, at least not in my experience. :-(

Personally, I used to get very good results with it, minding Dave's comment about pinholes though. Stephen is correct, however: the formula was changed, and is now nothing like as good as it originally was.

Promise... next time I go out to the shed, I'll try and find the old tin :)

I think you have to use an acid etch primer for this purpose, acid etch only needs to be inked over the surface to provide a suitable key, it does NOT need a heavy coating to obliterate the surface.

Stephen.

OK cheers,

In article , snipped-for-privacy@btinternet.com writes

I'm sure you're right!

Like a twit, I followed their instructions to the letter, and didn't test it somewhere first. I don't think I've still got the tin, as it was some while ago now, but I'll have a look and report back what it actually said.

But as I mentioned I did gently key the surface, either with wire wool or fine grade wet+dry (can't remember now) and degreased it. The liquid didn't wet the surface properly at all.

It will be interesting to see what the special metals primer consists of, etch primer however consists of Phosphoric acid so it burns or bites into the surface to provide that important key.

Sounds like you've done the prep right, maybe the paint is just crap.

Stephen.

I tried a hot air gun and it did work in places but where the powder coating stuff was still good(maybe half of the surface area) it was very difficult to get into the corners. Ah well, maybe blasting is the only practical option, that's going to be expensive!

I hate powder coating!

Interesting opinions on Hammerite, so what's the general opinion on a better coating. Bear in mind I've never used anything other than Hammerite in the past for rusty steel, so I'm ignorant here!

Thanks for all the input so far guys :o)

Neil

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