De-Chroming

[t3rmin]

I've actually found the hi-temp paints are less flexible. Dunno about "sticking strength", though.

[97Intruder]

Thanks!!

Thanks a lot guys....gave me some good ideas....I believe the sanding will be the best bet.....I'm doing a " test " now of just a cleaned & primed fender, and will be testing an acid etched, then a sanded,(all of will be primered) and will post the results....although it might not be for a while cuz I'd like to get as much riding in as possible before the weather gets too unbearable, so unless this thread stays active with other ideas, I'll revive it when I get the results.

[themess]

A friend of mine is an industrial chemist who has decades of experience running plating lines that have varied from decorative chrome on gymnastics equipment to circuit boards. Chrome plating is almost always applied over nickel plating, which sometimes goes over copper plating. Here is his answer:

.....immersion in a 25% HCl solution will remove the Cr in about a minute. I assume the chrome is over a nickel underplate which will be unaffected by the HCl. The nickel layer will have a slight yellowish tint, whereas the chrome will be silvery white.

The nickel is the problem. It’s a nearly pure electrodeposit so about the only thing that will strip it off is a very strong, very hot, very alkaline solution of sodium cyanide and formaldehyde. I don’t recommend it. Aqua regia would take it off but you’d damage the part

Instead, glass bead the nickel to make it frosty, immerse a few minutes in clean 10-15% HCl, rinse then dry with a heat gun (or rinse in a boiling kettle of water.) Do all of this very quickly in sequence. Before starting, see if you can get your hands on an acid wash primer. It will give better adhesion to the nickel. Once the glass beaded part is dried it should be primed ASAP. Dry nickel quickly develops a passive layer in contact with air which gives degrades paint adhesion. Glass-beading and acid rinsing the part activates this layer and the acid-wash primer activates even more. Make sure the proper air respirator for acids is used when spraying the primer. From there, it’s just another paint job.

If this is an original Harley part it will have a lot of nickel. A quality chrome plating job could actually have three layers of underplate, the 2nd one being 99+ percent, sulfur-free nickel which even the cyanide struggles with. Once the nickel is gone there could be a 3rd copper layer over the base material. Just about any acid will remove copper. If the base material is aluminum or die-cast zinc there’d be copper for sure. One of the challenges in stripping parts is to figure out what the base material is first then to choose a sequence of strippers to remove these layers completely and not attack the base material.

Note that he's talking about:
>sodium cyanide, the chemical used to kill people in gas chambers, >formaldehyde, which causes cancer
>hot, concentrated lye, which will dissolve flesh from bones.
>Aqua regia, which is concentrated nitric acid with a bit of concentrated sullfuric acid thrown in. Very dangerous stuff.

Hydrochloric (muriatic) acid, is tame by comparison.

[TheCafeKid]

Uh...yeah...I'll take sandpaper and paint for 400 Alex...

Repainting is easy...replacing flesh and bone is rather tricky...hehe

[97Intruder]

Great info.....thanks for the input, if it doesn't help me....it should certainly help others.....also, I think formaldehyde is also used in embalming if I'm not mistaken.

[n1elkyfan]

formaldehyde is used for embolming fluid.

I would definitly go with some 180 grit sandpaper then follow that up with a self etching primers. let the dry sand it with some 320-400 sandpaper prime it again with some normal primer. When thats dry prep and paint it like any other part.

[8trackmind]

Epoxy primer. It won't come off. Go to a real automotive paint and body supply store...Not Wal Mart.



This was a chrome fender. (still is really)

[themess]

Nice fender!

Formaldehyde is little used in embalming fluid anymore, for at least two reasons. First, it is carcinogenic. Second, it smells so bad that it brings tears to the eyes, even when diluted. Glutaraldehyde is used instead of formaldehyde.

(As a lab tech in college, I perfused and preserved some dogs as part of a veterinary biomedical research project.)

[t3rmin]

I think we're getting way too complicated here. Get the surface un-smooth so it has something to grip, and you'll be fine.

[Nessism]

I think we're getting way too complicated here. Get the surface un-smooth so it has something to grip, and you'll be fine.

Agree! Been done on bicycle frames for decades as standard procedure.

[tkent02]

Formaldehyde is little used in embalming fluid.... it is carcinogenic.

Does it really matter at that point?

[Steve]

That's kinda like sterilizing the needles used for lethal injections. :shock:


.

[themess]

It matters to the mortician, who is exposed to the formaldehyde vapors. And no one would want an open casket funeral if formaldehyde is used. Heck, no one would go into the mortuary. The stink penetrates wood carpet, fibers, even the surface of concrete.

But back to the original question: the summary is that roughing up the surface is the best way. Finer grit paper is probably better, too.