Prepping chrome for paint

[Normspeed]

I have some small chromed parts that I'd like to paint.  I know paint doesn't adhere to chrome very well.  Any ideas on how to get an etched surface on the chrome? These are odd shaped small parts so hand sanding is out.  Maybe a diluted acid dip, or put 'em in a rock tumbler with some sand?  I don't have access to a sand blaster.

[1FATGMC]

I'm also interested in this as I might want to do this to the parts on the Desoto.  My parts would be big though, like bumpers, and I do have a sand blaster.

thanks,

Sum

[enjenjo]

Well, platers use an acid dip to remove chrome, so that will work, but it's a bit hazardous. Myself, I usually sandblast it. They make inexpensive spot blasters that work fine for small parts.

[purplepickup]

I've been sand blasting bike parts that have thin, cheap chrome on them and painting them with good results.  Those little gravity feed hand held Speed Blasters work nice on small parts, like enjenjo said.  They're pretty cheap and a 90# bag of silica sand at the local brick layer's supply is only about $4. I try to just etch the chrome with the blaster to give the paint something to stick to but sometimes the chrome is so thin that it starts to peel.  I hit those spots with a fine flap wheel to smooth the spot then prime with epoxy primer which seems to stick real good.  If the surface is uneven I follow with a coat of 2K primer and sand then paint.  The parts look real good now, I guess we'll see if it lasts.  I'm pretty confident that it will.  

If I was doing a bumper I'd probably use the same basic method.  The worst that can happen is that you'd have to strip the bumper and start over, and that's probably the only other alternative to begin with anyway.

[1FATGMC]

Thanks guys.  If I was to sandblast the bumpers and paint them and then later decide to re-chrome them have I screwed myself up so that is a bigger job (minus the paint removal)?

My other problem is if I paint the bumpers and grill I would like to maybe paint some of the other trim (like around the windows) that I think is stainless.  Any thoughts there?  Can it be sandblasted lightly and then painted (epoxy and then finish coats) and still be polished up at some later date.

What I'm thinking is that the chrome on the Desoto's bumpers and grill is bad and would need to be redone and I don't want to spend that kind of money on the car.  I would like to make it a low maintenance driver and put it in black primer and do all the chrome and stainless in a grey color (like your headers George).

c ya, Sum

[enjenjo]

That shouldn't bother them Sum, you won't blast all the chrome off, just rough it up a bit. To rechrome, they will have to strip them down, and start over anyway

Stainless can just be sanded, like mild steel, it's not as hard a chrome.

[reborn55]

was also geting ready to paint some trim.  I have the interior trim that has been chrome plated and is dulling.  Need to repaint--seeing as they have already started to dull--do you think just sanding, priming and then painted would hold.  thanks

[enjenjo]

The problem with painting chrome is it's very smooth, there is nothing for the paint to bite into, to hold it in place. Sanding chrome by hand is for the most part, ineffective, because you can't scratch up the surface enough to make a difference, and you can't get into the crevices where the problems start. Without a good mechanical bond, sooner or later the paint will fail. And once it starts it's hard to stop.

The correct way to paint chrome is an acid etch, which is near impossible to do without closely controlled conditions, next best way is to strip the chrome, and prep like you would any other part. Again, acid is needed, and is really not safe for an amateur to do.

Next best thing is sand or bead blasting, with sandblasting being better, unless they are die cast parts.

[1FATGMC]

   

Next best thing is sand or bead blasting, with sandblasting being better, unless they are die cast parts.

How about Mr. Desoto.  I think he is die cast.  In the pictures he has frost on him, but he is pretty potted and I want to keep him.

   

c ya, Sum

[enjenjo]

I would glass bead that. It will still open up the pits some.

[bucketmouth]

Considering how much it cost to get a good bumper in the first place to chrome it might be more pracitable, especialy if you decide to rechrome it later to have a chrome plater strip it. The chroming process is reversed to strip chrome. Something worth considering.

[sirstude]

On my Studebaker, I wanted the outside grill pieces painted and they were chrome over pot metal.  I ran down to the high school and used their bead blaster on them.  I blasted them until they had a frosty look.  I then primed them with Dupont etching primer and then painted them.  I looked at the car this summer and they were still good after 12 years.

Doug

[BFS57]

Hello;
I have been preparing to do this for a while (info). I painted my rusty rear bumper on my 57 Chevy with spray cans, Been two years and it looks really fine (not perfect). From what I hear, you must use a self etching primer! First you scuff, prime with self etching primer, sand again, touch up, then spray!
I went to Turkey rod run last year and asked every car owner with painted bumpers I could find, How did you do that? Thats the answer I got!
Bruce

[purplepickup]

How about Mr. Desoto.

He is very cool ...and those are neat pictures with the frost.  It looks like he's still got good detail.  I'd sure try not to affect that if possible.

Does anyone know if pot metal continues to pit after it is repaired and replated or painted?  What causes it to pit in the first place?  Is it more than just oxidation?

[enjenjo]

Does anyone know if pot metal continues to pit after it is repaired and replated or painted? What causes it to pit in the first place? Is it more than just oxidation?

Yes it continues to corrode. The metal content varies, but most of it has a lot of zinc, which makes it more prone to corrosion. And it's an unstable alloy to begin with. I've had good looking parts stripped for chrome, only to find them full of pits, sand the pits out, only to find more pits under them. the plating process itself is at fault for  the pits, from the acid used in plating, plus there are microscopic defects in production  plating that allow moisture in to supply oxygen that accelerates the corrosion.

I was told by an engineer from Dohler Jarvis, who cast a lot of trim for the big three that it was never intended to last for more than ten years.