Cadmium for You, Cadmium for Me

Posted on November 28, 2014 by Jefferson Bryant in Interior, Paint/Body, Tech // 2 Comments

Protecting steel components under the hood can be a tricky proposition. Chrome is flashy, but too expensive for minor parts. Black oxide looks good for a while, but loses its rust protection quickly. Originally developed by airplane manufacturers (and still widely used for aeronautic components), zinc and cadmium plating became popular in the 1960s for underhood components. There are several types of plating, the two most popular for underhood parts are Zinc and Cadmium.

Zinc plating is more durable than Cadmium, and was used mostly after 1967. Like Cadmium, Zinc comes in several colors- Dichromate, which has the classic iridescent gold color; Black; and clear, which has a silver color. Cadmium plating is not as shiny as zinc plating. Colors of Cadmium are most often Gold or Yellow, but can be green, clear and black as well. Cadmium plating is dangerous, using highly-toxic chemicals and considered a severe environmental hazard. As such, getting parts Cad plated is not so easy, and Zinc plating is fairly expensive for small single parts.

Unlike Chrome plating, Zinc and Cadmium plating deteriorates faster, by design actually. Instead of letting the atmosphere attack the metal, the Zinc or Cadmium surface takes the brunt of the force, keeping the underlying surface safe. Eventually the plating gets thin and is used up; the substrate metal begins to rust. There are three solutions to this problem; replacement, re-plating, or paint. Since plating is not really an option for most builders and replacing an otherwise good part is just silly, we go to paint. For a restoration, painting a plated part any other color is not going to get you any extra points at a show. Luckily, the Eastwood Company has the solution.

The Golden Cad paint system is a series of four special paints, gold, red, green and clear. With practice, you can achieve near perfect results that can look just like the original surface. While the biggest component for plating is the vacuum power booster, other parts such as brackets, vacuum pots, lids and door hinges were plated. We spent a few hours in the shop with this kit and a couple of parts (two vacuum pots and a bracket) that needed some attention. As with any paint project, the final product will only be as good as the prep job done before the paint goes on, so take your time cleaning it up. This process takes a little bit of time to learn, so practice on some junk first.

01. This is a GM HEI distributor, while it may not be found on every classic car, these were commonly swapped in place of points-style distributors. The type of distributor is beside the point, as we are looking at the vacuum advance canister. This was originally plated in yellow Cadmium, but now it is just crusty.

02. First, we disassembled the distributor and removed the advance. These are not typically set to a specific point, so you can pull it out.

03. You can see on the hose nipple that it had been painted at one point, but there are still some remaining tell-tale signs of plating on the mounting tab.

04. Using some PRE prep spray from Eastwood, the parts were cleaned up. This is the bracket for a vacuum pot that we are restoring in addition to the distributor. A wire brush was used to knock off the heavy stuff. The PRE spray leaves no residue and works great for cutting grease. Engine cleaner works too, but you will need to clean it really good with soapy water to get the residue off.

05. Once the advance pot was cleaned, you can really see the original yellow-gold tinge. Obviously, this is not restored, just cleaned. We have a few more steps to go.

06. A scotch-bright pad (medium grit) was used to remove any scale, rust and other imperfections from the surface of the vacuum pot. Note the slight scratches on the surface. This gives the paint something to grab on to, you don’t want a slick polished surface, but you also don’t want it super rough either, which will show through.

07. Once scuffed, everything was wiped down with PRE again to ensure that the surface was super clean.

08. Ready for paint, the vacuum pot and bracket were placed on a clean surface. We used a cardboard box that we fashioned into a miniature paint booth.

09. It is a good idea to have a reference for plating. We used this drill guide from another project. This is a good example of what cadmium and zinc plating looks like. Our reference is flat, which does not help much for round and curved pieces, but we have done this before. A power brake booster or master cylinder lid are great examples. You can use catalog pictures as well.

10. First a light base coat of the Gold Cad spray. A light touch is needed here; this is a thin paint that runs very easily, so just mist it. We laid down two light coats to ensure solid coverage.

11. Once the gold cad was sprayed, we added some highlights using the red paint. This is a metallic paint, it will run and can splatter too, so be careful. We did not hang the parts because this helps you get an uneven coat, which is exactly what you want. Notice we only sprayed a couple of edges of the pot, and added some glancing shots to the bracket.

12. Next up is the green tint. This is really thin AND metallic, so it runs fast. You don’t need much of this, just a mist. You can place some highlights of green, but we have found that the best method is just a few misting sprays gets the tinting just right.

13. The green is most often sharpest on the edges and the peak of heavy bends and curves. This one is ready for clear. If you make a mistake or the red and green is too harsh, you can tone it down with a mist of gold cad. Sometimes that is just the thing to make it perfect.

14. You have to let the part dry and then roll it over to do the other side(s). The green works great to tone down heavy red highlights too.

15. This is the finished part before the clear coat.

16. For the clear, we hung the parts in the booth. This is where you want a nice, even coat of paint. Two light coats is all it takes, letting the parts dry about 20 minutes in between.

17. The finished vacuum pot and bracket. This is about as close as you can get to the real thing.