I have an alternator that has been chromed. I think it's an original open face unit that's on my 70 442 Conv.. Is there a way to remove the chrome without hurting the housing? I would guess that it had to be polished before chroming and it might not be worth the effort.

 

I don't think it worth the effort. They had to smooth it first so yes they polished it.

 

Removing chrome is a "reverse polarity" process. I am guessing they polished the case smooth to give a "show" chrome look. "Blasting" with shot or glass beads after the plating is removed that could possibly give a "cast" finish. It may be easier to find another alternator and clean it up.
.....Just my two cents worth.

 

Ralph is correct. When you get something replated, the first thing they do is to strip the chrome using the reverse of the electrochemical process that deposited it there. If this was a show chrome job, then they should have polished the part first. The electrochemical stripping should not harm the base metal, but you won't know what's under it until it's stripped.

 

I wonder if it has been polished and the chrome removed like Ralph says can it be sand blasted to give it a natural look? This is one of those rare open faced units that are expensive and hard to find.

 

Yes, but the question is, how well will the blast surface mimic the original cast finish? I've seen people use an vibrating engraving pencil to mimic the rough cast finish where they've had to make weld repairs to aluminum castings. The problem is that doing this over the entire housing will be tedious. Your call in if the cost of the part, stripping the plating, then hand-finishing to replicate the cast finish is economically viable, even for such a rare part.

Scroll to the end of this video where he uses the engraving pencil.

 

It's a hit or miss proposition/process regarding removal of chrome (chromium=Cr) to a desirable finish. I am not familiar with the process employed to chrome plate this specific alternator - was it a factory process &/or aftermarket process & exactly what elements were used during the plating process - nickel alloy, zinc, copper, etc?

You "could" remove each of the metals employing reverse electroplating techniques if you know what you're doing and have the available equipment. Like any electroplating process you're going to add a metal or remove a metal based upon the elemental state of the ions which comprise the metal. Example: free ions (electrons) exist in a lead battery solution of sulfuric acid & we use those free ions (electrons) to perform work between the anode & cathode of the battery (both comprised of lead). Electroplating is very similar in simple terms - you either ADD electrons (ions) to a metal; or you REMOVE electrons from a metal. The trick/key is to know the electrostatic valence of the metal(s) being used. Maybe enough chemistry for now.

If you're NOT going to employ reverse electroplating, you can use a combination of acids. Just remember each type of acid is being used to remove a particular type of metal and this is based (sorry) on the electrostatic valence of the metal. Valence simply means adherence of electrons to remain attached (for lack of a precise chemistry explanation).

HCl (Hydrochloric Acid) will dissolve Chromium (Chromic Acid) in a heartbeat. However, it's the concentration of HCl which establishes the rate of the reaction. You most likely know Muriatic Acid (laymen term) is known in chemistry as HCl (Hydrochloric Acid). You'll need (in practical terms) a rough concentration of ~30% - 40% HCl to effectively remove the chrome plating. This should take anywhere from 5' or 60' to remove the chrome plating (depending on the underlying metal and thickness of the chrome plating). I believe the consumer containers of muriatic acid are roughly 33% to 37%.

Depending on the underlying metal (nickle, zinc or copper) determines the next step. HCl is completely inert (will not react with) Cu (copper); therefore, HCl (Muriatic Acid) will not remove an underlying copper plating (if copper was used in the chrome plating process). To remove the copper (if that's the underlying metal) you'll need sulfuric acid at a concentration of roughly 20%.

If you want to test your skill at this - it's quite simple. Take a handful of known good chrome plated nuts, screws &/or bolts, etc. (door hinges are great examples if they're chrome plated) then place them into a glass jar of HCl (i.e. full strength consumer level muriatic acid). You'll rapidly witness the chrome plating dissolve into solution. If the underlying metal is copper, the reaction will stop completely. As stated, HCl will not react with copper. At this stage, if the underlying metal is copper, next rinse the hardware in water, and place the same hardware in a clean glass jar of sulfuric acid. You will then witness the copper dissolve into solution. There really isn't anything mysterious about electroplating. Sure, you can change the state of charge (anodes/cathodes) and the temperature(s) of the solution, but essentially you're going to use an acid-based solution of either HCl or H₂SO₄ (sulfuric acid) to remove the metal. Where gloves and a mask and experiment - you'll note some interesting results. Regarding getting to a finish which might resemble the base underlying metal? Most likely it's going to be aluminum - could be steel, not sure what they used on this alternator.

In each of the processes identified above, always rinse the metal in water. A thorough rinsing in water will stop/halt the reaction. Sulfuric acid can dissolve aluminum but it's a very slow process - you can stop this process (once again) by a thorough rinsing in water.

 

BTW, when working with high concentrations of acids, always remember this saying:

"Do as you outa, add acid to water"

Never add water to a high concentration of acid. At the consumer level you most likely aren't going to involve yourself with an explosive event; however, it is easy to cause highly concentrated acid solutions to "splash" (this is in fact an explosive reaction - mild as it may appear, it is an explosive reaction).

 

Its NOT a hit or miss process, plating shops know what they are doing to remove chrome or other plating !!!!!! Your copy and paste from some site was not helpful and actually provides useless information. You really shouldn't comment on things you know absolutely nothing about.

 

You should really SHUT YOUR PIE HOLE when you know ABSOLUTELY NOTHING about chemistry. The fact you know NOTHING is easily ascertained by your response.

 

The question was not about chemistry. In your efforts to impress people, when in fact you know nothing about the subject is apparent. Keep using and misusing the big words if you like.

This was posted a while back and you still haven't learned:
Norm, from my view point; I took the time to write a response to the OP based on my knowledge and experience. I only respond when I think I can help, not shoot from the hip, not spew wrong information, not trying to impress people by writing five page masterpieces, using big words or acronyms that few if any people understand. What do I get in response? A post challenging my repair suggestions that was so wrong I couldn't believe it was ever written. I write from memory what I did forty years ago in an effort to help the OP and here comes another response that includes pages from the service manual in an attempt to one up me by mincing words.Then yet another post criticizing my choice of words. Wow. What does the OP get? Confused by wrong information. Remember the whole point of of the thread is help the OP. I prefer to only respond to the OP. Look what became of this thread, confusion and fighting all because of egos. I'm spending more time responding to challengers, egotists and cry babies then I spent with the OP. Heck if the OPs car was in my driveway it would have been fixed by now using the repair I suggested in the first place.

 

Refer to Post 10

 

READ Post 11 and try to learn from your peers.

 

The OP's thread is titled "Stripping Chrome". What I correctly articulated was the process of "stripping chrome".

The OP (also) questioned:
The question involves chemistry if you want to strip chrome. Plating shops would not exist w/o the knowledge gained from chemistry. The fact someone doesn't understand chemistry evidently provides basis to berate others who do understand chemistry (evidently).

 

READ: Post 11 and learn or continue as a 10 cent mind using 2 dollar words.

 

Y'all are pretty high strung. Go take those Olds for a ride--it might relax you.

 

When you have nothing good to say....say nothing.

 

Actual chrome plating is only around .0003 thick. That is not a typo. That is 3 ten thousandth of an inch thick. Think of it as a transparent clear coat on the under lying plating. As as Norm articulated it can be easily stripped with a quick swim in a muriatic acid bath. Keep in mind that the inside of casing is bare and the acid will eat it away in short order and leave a nasty black finish.

But now you are still most likely left with a nickel plate over a copper plate. Removing these will require some professional help and I doubt you will want to pay the price IF you can find a plater to take on the task. You still have a polished surface that will be unnatural appearance.

I would sell this item to someone who wants it like it is and find an original and rebuild it to fit your needs.

tc

 

After further investigation the chrome alternator I have is not the correct unit for the car. Finding the correct unit is very hard for sure but I'm looking. Thanks to all who gave advice on this subject.