The various engine components in our Redline Rebuild series can spend hours sitting on tables before they’re assembled—and Davin often assembles connecting rods, timing gears, and other small parts several times to capture the action from multiple angles. He has a few tricks to keep assemblies in good condition, particularly when they may be handled multiple times and stored in the open. Today, he’s walking you through the process of using black oxide to protect steel parts.
Black-oxide coating essentially uses one form of corrosion to prevent another; it is not a coating per se but a controlled form of oxidation. Red oxidation is commonly known as rust, and black oxide can keep it at bay. The process doesn’t actually oxidize the metal; the cold black oxide “coating” comprises a very thin layer of copper selenium. This compound prevents rust from forming on the steel and also gives the part some resistance to mild abrasion.
Black oxide is also easy to apply. If you purchase a kit, you’ll need nothing more than some careful water dilution and a pair of gloves. Davin starts with connecting rods that have already been cleaned and sandblasted, but your first step will likely be a chemical cleaner (imagine the paint process, which starts with a wax and grease remover). Once the parts are cleaned, the second bath is an etching wash. Then, Davin places the parts in the oxide solution that deposits the copper selenium onto the parts.
The darkness of the coating varies depends on how long the oxide solution sits on the parts. More is not necessarily better; Davin simply waits for a good even coating and then rinses the parts with clean water before drying them. For external engine parts that won’t be coated in oil, the fourth and final step is a sealer.
Black-oxide coating is a relatively simple process that you can do at home to keep your engines and other pieces looking great for years to come. Of course, if you want to see more tips like this and follow the Redline Rebuild process, be sure to subscribe to the Hagerty YouTube channel to be notified as each new video comes out.