A Chrome Primer
By Bobby Baker
Bobby Baker, of Superior Chrome Plating Inc., chrome plating and other services conducted a special forum for us. He proved this tech tip on information about the basics of chroming.
I Thought I would address some general questions and describe the chrome plating process for those who are unfamiliar with how it's done. First, some definitions:
Chrome -- The word "Chrome" is an automotive slang term to describe the bright work on our cars and trucks. It's short for the base element Chromium (CR on your high school elements chart). Chromium is a very hard element (800 to 1000 VHN - very hard!). It does not provide the mirror finish. Chromium is actually the coating placed over polished nickel to protect it from tarnishing, scratches etc. Decorative chrome thickness will vary from a few hundredths of a mil to 1 mil.
Decorative Chrome vs. Hard Chrome -- Decorative chrome, of course, refers to the bright work Hard chrome is the same element, Chromium, placed over industrial machine parts to provide a protective covering. Hard Chrome usually has a dull yellow finish. The only difference is the nickel undercoating and the thickness of the chromium applied (1 to 50 mil for hard chrome).
"Triple Chrome Plating" and "Double Nickel-Chrome" -- "Triple" refers to the three metals involved (copper, nickel and chrome) but the terms really mean nothing ... they're sales gimmicks to make one shop sound better than another. Everybody hears about "triple chrome plating" but with today's technology, copper is no longer needed on steel parts. (Like our cars today don't use ethyl gasoline.)
Here's the short version of how a bumper is plated:
1. The bumper starts in a chemical bath to strip old paint or chrome. (Or bead blasted depending on part)
2. A "Straightener" removes any dings, bends, dents, cracks, etc. -- Basically getting the bumper straight and solid.
3. The "Grinder" smoothes out any rough spots.
4. The "Polisher" give the bumper a completely smooth finish. (MOST IMPORTANT STEP, more on this below)
5. The bumper then enters the plating line where it is thoroughly cleaned. (Pot Metal will go into the copper tank next)
6. It is placed in the nickel tank for 60-65 minutes.
7. After that it is placed in the chrome tank for 20-30 seconds. (Yes, seconds. Any longer and the chromium is too thick and the bumper would look yellow.)
8. The the bumper is allowed to dry and wrapped for shipping.
1. The NUMBER ONE question should always be: "How much experience does your polisher have?" The polishing process is an art and a chrome shop lives or dies by how good the polisher is.
2. Next ask, "How long do you leave a part in the nickel tank?" Nickel is the most expensive material in the process so some shops try to save money by using a very thin layer of nickel.
3. Last, "Will you do the prep work?" Good shops will always want to do the prep work. They would prefer that you send them the piece straight off the truck and let them clean it. Tip: Before shipping a part be sure to remove all nuts, bolts and brackets. The shops don't want to keep track of parts their not plating.
Have more questions? Post them on the guest forum or email me directly from my web site. Always happy to provide an answer or a quote. ~~ Bobby
* Editor's note: If you are unfamiliar with the plating process, you should ask many more questions! A reputable chrome platter will be glad to have the opportunity to help you understand the chrome process so that you do not have any disappointments due to erroneous expectations.
Be sure to check out our extensive Forums discussions -- from General Truck talk, Electrical Bay, Big Bolts, Panels and Burbs, Engine and Driveline, Paint and Body, Interiors, Tool Chest -- The Stovebolt Collective can help in your quest and walk you through the mire and magic of working with old iron. ~~ Editor.
v. Feb 2005
|No parts of this site, its contents, photos or graphics may be used without permission.||