Technical Prepping parts for chrome

This is the process ford used on there bumpers and gt wheels,
The chrome plater was in Monroe Michigan
It was 1/4 mile long,they first used it in 1957 and used it until they stopped plating bumpers( except for trucks) that business went to American bumper manufacturers out of Dearborn Michigan
They had first cells that cleaned the bumper after they were stamped out in the press department,then it was copper strike
Then a real shine copper,then every bumper was checked for imperfections,
Then they were plated with white br***,
Then nickel,
Then finally chrome
And final wash and inspection

 

The platers wouldn't do copper on my nerf bars. Said the chemicals would get into the holes in the tubing I had for my license plate light would contaminate the chrome tank. Who am I to argue? It's magic.

 

So, what was your final grit on your prep?

 

Not all plating shops work the same way, especially since the EPA put a death grip on the industry with many shops closing, rightfully so due to the careless way some shops were disposing of their waste.
A valuable note, ask the important questions, don't make ***umptions.
I looked for quite a while for a nice set of original L79 Chevy rocker covers, the OEM covers never were show chrome and I was fine with that.
I decided to look for a pair of painted covers that were worthy of chrome, I finally found a really nice pair at the Portland Swap Meet, I took them to one of the better local plating shops, it took nearly a month for them to get to them, I was ok with that part.
What I did not expect was for the letters to lose their crispness, apparently the copper polisher was a bit overzelous on the buffing wheel and the letters came out kind of flattened and mushy looking.

 

One thing I was told beyond the obvious was to remove sharp edges.

 

I'm betting you didn't get that at Harbor Freight!

 

So is there a particular compound that you used? I am always leery of contaminating the surface that is going to be plated.

 

Platers thoroughly clean parts with a caustic bath before they are plated. Platers can't afford to have their tanks contaminated.

 

Are you calling industrial (hard chrome) platers or ones that specialize in cosmetic (decorative chrome) plating? Since the former are after the chrome's hardness and abrasion/wear properties. They don't care about how pretty the chrome looks, so they aren't going to use a copper underplating which would require subsequently thicker chrome layers to counterbalance the softness of the copper.

 

Agree the issue is cyanide copper plating bath vs acid copper bath. EPA not very accepting of cyanide baths, almost all plating shops conversion to acid copper. The nickel and chrome are both acid bath already. So easier to deal with the waste and clean up from the baths being all acid baths. Chrome baths are even mostly trivalent instead of hexavalent, for same hazardous materials reduction.

Also good point that you want decorative chrome, not hard chrome. Decorative is copper, then nickel, then very thin chrome for appearance. AKA triple chrome.

As for your prep, it's labor at the shop vs your time. The better you can get the parts, the better results and cost. Ideally you want a steel part that is polished like a mirror. The chrome plating will show any defects underneath the plating, unless you do the right preparation. Either by you or the shop.

 

I bought mine around 1991 from MSC, have logged thousands of paid parts finishing on it. I use it mostly for polishing car chrome these days. I covered the exposed shaft and nut with shrink sleeve in case of an oopsie. I need to make up a shaft extender for at least one side.

 

No, we are in the heart of oilfield country so we have tons of industrial platers and powdercoaters. I'm talking about shops that do chrome for cars, semis etc. People just ***ume that everyone still uses copper, but they don't. Most shops that do offer copper call it "show chrome". It's substantially more expensive.

 

Found this on a guy's website. Has some good info in it.

Stripping
Before any repair work can be done to your part, all old surface finishes and contaminants must be removed. Grease and oil are removed in a parts washer that is serviced by a waste reclamation company. Paints and powder coating are removed by a hot tank stripper or by a dry blast method. Existing plating is removed by reverse plating in a 55 Baume solution comprised of sulfuric acid, water, copper sulfate, and glycerin. Rust is removed by blasting and/or pickling in hydrochloric acid. Whatever the requirement, Paul’s has several suitable removal methods available that are designed to remove the previous coating without damage to the substrate itself.


Surface Preparation
Plating only looks as good as the surface that it is applied to. Any deviation in the surface will mirror up and be magnified by the application of bright plating. Therefore, straightening, grinding, sanding, detailing, and buffing are extremely critical steps in determining the final outcome of the re-plated part. At Paul’s we take great pride in our ability to perform these tasks. Our ability to train new employees and retain our experienced ones is the prime reason that we have been able to grow, while providing consistent results project after project. It is ability (hand-eye coordination) and employee pride and determination that sets our work apart.


Surface Restoration
When deterioration is beyond removal by conventional sanding and buffing without risk to the substrate or its detail, the surface needs to be restored. This is accomplished by applying a substantial soft copper plating followed by a re-sanding. If required, remaining pitting, scratches, holes, or low areas are then silver soldered. The solder is then "cut down" to be level with the copper surface, and then the item is re-copper plated, enabling the entire surface, including the area previously soldered, to be polished. Depending upon inspection, the part will either have the copper plate reapplied and reworked, or have the final triple plate applied.


Plating
Cleaning - In order for plating to properly adhere, the substrate must be completely free of all foreign materials, such as oil, buffing compounds, finger prints, and soap films. At Paul’s the process begins in an ultrasonic cleaner tank containing a special hot buffered cleaner. This process removes virtually all the foreign materials, including buffing compounds, even down in threaded mounting holes. The part is then transferred to the scrub tank where it is meticulously hand washed to be certain that it is completely clean.

After a thorough water rinse, the item is then racked or wired to a copper hook. It is the rack, or the hook & wire, that will allow the electrolization of the piece in the various plating tanks. The cleaning is continued at this point with a dip in a dilute acid & water bath, to ensure the removal of any soap residue, as well as to activate the molecular surface of the part. This dip is followed by a clean water rinse, and the item is now ready for its base coat in the copper strike tank.

The copper strike covers down in recesses where other plating baths will not reach. The copper layer’s function is for adhesion so that the subsequent nickel plating or acid copper plating, which have an acidic base, will not react with the substrate, creating the potential for lack of adhesion (peeling).

Upon completion of the strike and accompanying rinses, a layer of acid copper is plated. This is a soft, ductile, thick layer of copper used to resurface the part, to prepare it for further work in the polishing department. If further work is not required, the copper struck item goes to the nickel solution where a heavy layer of bright nickel is applied. The nickel is the main corrosion resistant or protective layer applied to the item. It is also the layer that provides the decorative "bright" effect to the item.

The last step in the triple plate process is the chrome plate. This is a thin, translucent layer of a hard, weather resistant metal. The chrome’s main purpose is to prevent the tarnishing "dulling" of the bright nickel. After rinsing, the chromed object is ready for final inspection.

 

I worked in a chrome shop plating trampoline frames, gymnastic equipment and weight machines. We plated with a dull nickel followed by a bright nickel before the chrome. The dull nickel took the place of the copper plating, that we did not use, to help smooth out the substrate. Everything we plated was polished before going into the plating baths. For years it was a hexavalent chrome bath but towards the end of my employment there they switched to a trivalent chrome bath. although more environmentally friendly the trivalent finish was very disappointing compared to the hexavalent finish. On the gym equipment it wasn't so noticeable but on our personal car parts that we were allowed to chrome plate it was like night and day. I also learned early on that polishing is the most important step. Without a good polished finish on the substrate before going in the plating baths, the part could look like silver spray paint. I got pretty good at polishing my car parts, either using the company's polishing equipment or the polishing equipment I set up at home. As far the "light" plating in crevices and folds such as the flange on a valve cover, that is because it is a low density area that the electrically charged nickel and chrome has trouble getting into. The electrically charged nickel and chrome would want to go to the high density area first which sometimes would cause excessive plating (or as we would call it "treeing") in that area. We would build "robbers" to put next to these high density areas to eliminate the treeing. We would also build axillary anodes to put next to the low density area to help throw more nickel and chrome to that area. In a nut shell for decorative chrome plating of car parts - a good polishing job if the bare substrate is the key for good plating, the guy racking the parts with an understanding of low and high density areas is worth his weight in gold, use a plating shop that uses a copper strike and always use a plater that has a hexavalent bath.

 

I clean and sand (down to 2000) most of the parts I take in for plating. One, it saves me a buck or two. Two, I get my stuff back faster. Three, I catch imperfections that I may be able to weld and file away.

My chrome shop doesn't get rich off my onesy, twosy projects. The big jobs like semi manufacturers keep the doors open. So I try to make my stuff easy for them to get to.

And they have no way to remove powder coating, so I take those pieces to the sand blaster or throw them on the barbie for a while and burn it off. The more you do to prep the pieces, the nicer they turn out too.

 

I still need to send you those Caddy covers.

 

Before or after you dimple them?

 

After....They are actually starting to flash rust. Been sitting there for a year on the bench.

 

Years back a HAMBer shared a polishing handbook .pdf - I'll look through my email and report back if I have it. It was good stuff.

 

Every chrome shop I have ever used has always offered both: Standard Chrome -no copper and Show Chrome- copper.

 

@polisher ?

 

So are you saying he’s not gonna reply?

 

I’m thinking he was the one who did the instructional handbook. And I think he also p***ed away. His last posts were about selling his chroming equipment because he had cancer.

Edit: The booklet is on page 4 of this https://www.jalopyjournal.com/forum/threads/metal-polishing-booklet.57098/page-4

 

After reading that my question is how did they wire these shafts for tank to tank transfer without effecting the machined surfaces?

 

These were really pivot pins, nothing more or less. Nothing went through them.