In metalworking and steel fabrication, iron residue is an unwelcome but pervasive presence. If you've ever bought anything made of stainless steel that suddenly rusted, you have iron residue to thank for that, and every factory manager and worker has seen more than one piece affected by the residue. Customers may not fully understand why iron residue is such a problem, but it is, and they need to arrange for any metal parts that they don't want rusting in the future to be finished, even if the metal they're buying is normally not rust-prone.

Residue Deposit Sources

Iron residue can come from any iron tools or grit that touch the metal. When the iron hits the metal, it leaves microscopic bits of iron behind, and these bits can stick to the other metal's surface, rather than sliding off. Iron residue can also be in water, so using water in the machining or metalworking process can actually leave behind deposits. Iron residue can even float through the air, landing on metal nearby.

Why This Is Bad

For those who are new to dealing with metal, iron residue is what leads non-iron metals to rust. If you've ever had something made of stainless steel, like a dishrack or knife, and have found it covered with rust spots after a while, what you're really seeing is the rusting of a layer of iron residue on top of the stainless steel. This is also why you can clean off the rust easily; if the metal itself were rusting, you wouldn't be able to get rid of the rust so quickly. On industrial metal, rust can gum up machines and just look awful.

Passivation as a Solution

For stainless steel, metal finishing using a technique called passivation that can help stop iron residue from ruining pieces. In passivation, the steel is cleaned thoroughly to remove iron residue, and then it's dipped into a chemical bath that covers the surface of the metal with an oxide layer that prevents additional rust from forming. The passivation not only gets rid of current iron residue but it also effectively seals any chips or scratches in the stainless steel that might otherwise expose internal iron in the alloy.

If you need metal parts, especially those made from stainless steel, be sure each part goes through a finishing process. At the very least, the finishing process will protect the metal from corrosion, if not also add color or shine. Reach out to a professional who provides metal finishing services for more information.