As a rule we in this industry are a self-sufficient group. We build our own engines. We do bodywork for ourselves. We build frames. We paint our own cars. A few of us have even taken to trimming our own interiors. But there's one frontier we can't seem to conquer: chrome.
For good reason, really. Chrome plating solutions contain strong concentrations of sulfuric acid. The process relies on hexavalent chromium and produces lead chromate and barium sulfate, three toxic chemicals that'll kill you in time. One solution will kill you immediately: it contains cyanide. No wonder it costs so much to have parts chromed.
So for that reason I sort of knew what to expect when I asked Don Meth at Show Quality Metal Finishing what it would cost to have a few pieces made bright. But what I wasn't prepared for was the cost if I prepped the parts. While not as inexpensive as having a part powdercoated (frankly nothing is anymore), it wasn't much more than it would cost to finish something in a modern two-pack paint.
As ironic as it seems, it's not just the cauldrons of potentially gene-altering solutions that make plating so expensive, it's the preparation. You see, highly reflective surfaces amplify flaws so the scratch that goes into a tank emerges a canyon, or so it seems anyway. And to work a part to that sort of finish takes time. And time costs money. So reduce the time a plater spends on a part and the price comes down dramatically.
My eyes sort of glazed over as I pondered the things I suddenly could afford to plate. But I came out of the ether pretty quickly. I don't have a buffer much less the wheels and compounds they require. Meth interrupted me, "I don't even use any of that stuff to prep parts for chrome." As he explained the methods he uses I realized that I already had most of the tools to prep parts for plating. "Just come down to the shop one day and I'll show you," he offered.
Here's metal finishing in a nutshell: reduce the surface flaws with a series of abrasives, each step finer than the last. Take a cast part for a start. Eliminate the casting grain with 80-grit abrasive. Replace the 80-grit marks with 150-grit abrasive. Then rub out the 150-grit marks with 220. And here's the jaw-dropper: at that point you're done prepping for chrome. "Anything finer than 220 is usually a waste of time," Don reveals. "If we're doing a really critical part for a show car we might go to 400 but only so we can see if we left any marks coarser than 220. But 220 is just right." As our good fortunes would have it, nickel and chrome build enough surface finish to fill the fine scratches left by 220 abrasive.
In other words, take the notion of using a polishing wheel and a bunch of compounds and throw it right out the window; that stuff is totally unnecessary according to Don. Though he uses a wheel to achieve that finish, understand that it's a 220-grit grease wheel (often referred to as a setup wheel) and not a polishing wheel (we'll show you how to make one too). What it takes to work up to that 220-grit surface is your prerogative. Be it a cartridge roll or a surface-conditioning disc on a die grinder or just a sheet of sandpaper wrapped around your finger, whatever it takes to work up to a 220-grit finish is just fine. "You got a DA sander, right?" Meth asked. "That's all you need for some stuff."
1. Chrome and nickel plating are removed electrochemically, but not the copper. That’s a mechanical process. Don Meth says 150-grit abrasives work quickly but won’t gouge the base metal.
2. Meth’s belt setup is a monster but The Eastwood Company’s expander wheel (PN 13079) fits common grinders/polishers and accepts abrasive bands and Scotch-Brite belts. Its face conforms to complex shapes to prevent gouging.
3. Meth’s belt setup is a monster but The Eastwood Company’s expander wheel (PN 13079) fits common grinders/polishers and accepts abrasive bands and Scotch-Brite belts. Its face conforms to complex shapes to prevent gouging.
4. Removing plating reveals numerous flaws. In this case a spot of copper revealed a low spot, a dent. Plating will only amplify such flaws. It has to go.
5. Metal finishing, whether body panels or bright work, relies on the same principles. Don uses a chunk of I-beam as a dolly and using the off-dolly method raises the dent from the backside with a pick hammer.
6. Dents stretch metal so raising one creates a slight ridge. Confident that the dent sits flush Meth knocks down that ridge and the tool marks with 150-grit paper on an orbital sander.
7. After a few moments under the sander all traces of the dent disappear. It would take heaps more time but Meth could use the orbital to remove the copper and then make the part plate-ready with the 220.
8. Meth then fires up his grease/setup wheel. Refer to page 32 to learn how to make one of these incredibly powerful sanding tools. They require a lubricant (tallow—the stick he’s applying) to stay clean and not overheat the metal.
9. The grease/setup wheel behaves like a cross between a buffing wheel and a sander. Though he didn’t do it here Meth recommends alternating sanding directions with each grit, say lengthwise with the 150 then diagonally with the 220-grit grease/setup wheel.
10. Displaced metal loads up the grease/setup wheel and diminishes its action. Meth ran it across a big patch of copper that he usually would’ve removed with the 150 belt to show how a loaded-up wheel looks. It barely worked at this point.
11. So Meth once again ran the tallow stick across the grease/setup wheel’s face. Warning: the stuff smells like a bucket of tripe under a porch after a county fair.
12. The heat generated by friction melts the tallow, which dislodges the metal impacted in the abrasive (and develops the full scent profile). The grease-laden metal particles fling pretty much everywhere thereby broadcasting the fragrance.
13. It still has traces of copper and abrasive schmutz all over it but the presence of nothing but 220-grit sanding marks indicates that at least a small patch of this part is ready to go into the plating bath.
14. The only difference between these control arms is that the left one hasn’t taken its bath. Meth’s guys took this one to 400-grit just to guarantee that they hadn’t missed any sanding marks coarser than 220.