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Chroming
by Michelle Gladstone
I thought I would do a little research on chroming. Most of us are in that mode where we are either in a restoration or starting to make parts on our cars look pretty. I have noticed in conversations that Jesse and I have had with fellow Z'ed friends that a lot of people are kind of unsure about the process including myself. So this is what I found.
A little trivia 1st - did you know that most people think of chrome as the bright shiny stuff on bumpers. This is not chrome, however, it is nickel. The chrome is like a clear coat over paint to keep the nickel from turning color!
Proper chroming is indeed a process and most jobs are very similar. Depending on the condition of your piece that you are getting chromed (whether it needs any metal repair for rust) and the fact that some of your chrome shops have their own special process on their prep or how many times they may coat your piece is the only difference you should see.
All parts will be striped - Chromed parts will require one kind of stripper, while painted steel and aluminum need another.
In general the process begins (after any repair is done) with polishing the part to a fine luster clean of any impurities and free of rust, excess weld slag etc. This helps seal in impurities in castings and prevents the subsequent plating from "dropping into" minute surface imperfections in the material. Cast wheels particularly must be carefully polished to seal the surface and provide a smooth face for the nickel and chrome plates.
Next comes a plating of copper buffed. This soft metal helps seal in the pores of the metal and provides a smoother surface for the following material to adhere to. If you've seen bad chrome jobs that are full of pits, you can bet that either the polishing or copper-plating job was done hurried.
The metal (i.e. copper or nickel) is adhered to the metal by going into consecutive tanks or baths of alkaline, water, acid, then water with an electrical current that travels through a titanium basket filled with your part and either a copper or nickel ingot - by this process it turns your part almost into a magnet with the current going through it which coats your part with the specific metal (nickel or copper).
*Special anodes--which resemble pencil-thick wires are used to provide a positive charge near the to-be-plated surface-which in most cases is fit into the wheels or other parts to help evenly distribute the electroplating materials.
When placed in the chemical bath, the item to be chromed is subjected to high-voltage, low-current electricity to promote deposition of the plating material from sacrificial anode to the item, which is the cathode.
After the part is coated with copper it is then polished /buffed again. Then it is ready to go through the baths again - this time coating the nickel - a thicker coating means longer time in the coating tank/bath.
The part is buffed again, then the whole process is repeated with the final coat of chrome; the clear coat. Depending on the shop you go to will depend on how many coats of nickel they will give you - obviously the more the better.
*Three main questions you should ask of any chrome shop.
1. How long has the shop been in business? A guy who's just starting has a lot of learning to do.
2. What kind of guarantee does the work include? Some shops offer a year; some shops only guarantee the surface for three or six months and some offer a lifetime guarantee to the original purchaser. (You have to have confidence in your work to do that).
3. Find out how the chromer tracks the parts. If there is a batch of similar parts been done at once -you don't want to get someone else's parts not knowing if they have been abused or how old they are. Some shops even photograph every part that comes in for certification and keep the work orders separate throughout the chroming process.
© 2007 Triad Z Club
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