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Keep Your Steel Shiny with Chemical Polishing

Updated on April 30, 2013
Stainless steel is one metal that benefits from chemical polishing to protect it against rusting.
Stainless steel is one metal that benefits from chemical polishing to protect it against rusting. | Source

They say diamonds are a girl's best friend, and I have to guess it's because they're so shiny and sparkly. In the same vein, I'd have to say that shiny chrome on a car is a man's best friend (next to his dog, I suppose). Shiny metal looks classic and expensive, but it's also indicative of metal that's been treated to be rust-proof. If you've never heard of chemical polishing, well, that's generally the process used to protect metals from the elements.

It's used in many different industries, and has plenty of benefits besides just keeping metal clean and shiny. In this hub, I'll teach you about how the process works as well as what its benefits are, aside from the old "shiny" thing.

What is Chemical Polishing?

Chemical polishing can also be referred to as passivation, and what it is is the process by which metals are made to be resistant to damage caused by the elements. When a metal is chemically polished, or passivated, it has a barrier of chromium oxide that protects it from rusting out. The way it works is that the metal is introduced to a chemical, usually an acid, and that acid reacts with the chromium in the alloy and exposes it to oxygen in the air. The chromium reacts with the oxygen to form chromium oxide, which acts as a barrier between the air and the metal underneath the barrier. Metal that has gone through this process are "passivated," or made to be non-reactive with air, water, and everything else they might come into contact with. If the surface becomes scratched after passivation, as long as nothing is embedded within the scratch, the barrier can reform itself. When the metal becomes scratched, all that happens is more chromium is exposed to the air, which, again, creates the chromium oxide barrier. If, however, this happens on metal that isn't passivated, for example, your car which is coated with paint instead of being passivated, when scratched, there is potential for rust to form.

What Products Are Used?

Typically, companies use acid to carry out the process, either nitric acid or citric acid. Both are popular within the industries that offer the service, but nitric acid requires those employers to provide their workers with the proper safety equipment to handle it, as well as pay for hazardous waste disposal. With citric acid, the requirements are a bit more lax as it is not as dangerous to work with.

Why Should Companies Do it?

Companies that are looking to extend the life of their metal parts should look into chemical polishing services. Especially with parts that are made to bend and flex—like springs—rust can be very damaging. While rust might look like it's just on the surface of a part, like icebergs, more rust is hiding beneath the surface. In the event of this happening on springs, say, in your car's suspension, when a part rusts through it has more tendency to snap and break—prematurely. Passivating metals means they'll last longer because rust won't be corroding them. If your company wants to take things one step further, there's a different process called electropolishing that takes things a step further. With this process, not only is the metal passivated, but it's also smoothed out to a uniform surface, which is ideal for things like medical tools and dentists' equipment.

Industries that Utilize Chemical Polishing

If you've ever seen a ship out at sea looking perfectly painted against the ocean, there's almost a certain chance you're seeing metal that's been through a passivation process. Metals that have to stand up to the elements all the time are especially good candidates for the process. Industries like the automotive and aerospace sectors utilize this technology, as cars and airplanes are subjected to air and water nearly constantly. While cars get a layer of paint, the undercarriage has to be able to maintain integrity, otherwise no one would buy cars.

Electronics also use the process, and perhaps the most surprising ones that uses passivation processes on its equipment is the food & beverage and the medical industries. Since bacteria growth can harm both of these industries significantly, keeping metals rust- and corrosion-free is absolutely imperative. Since rust can harbor bacteria and the tetanus virus (did you ever cut yourself on a rusty nail as a kid and then have to get a shot? That's why), these industries use chemical polishing and passivation to keep their metals in tip top shape, working as they should for optimal safety.

Though it sounds like it's a complicated process, it's far more common than you might think. It's certainly beneficial to a handful of different industries, and if you really wanted to, you could even get your old rusty tools passivated so they last longer, too.

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