Passivation for Stainless Steel Parts & Enclosures

Every week, Team Protocase is bringing you a Proto Tech Tip video, where we’ll give an informative look at a particular aspect of sheet metal fabrication and CNC Machining.

This week, Cody from our Engineering & Design Services team discusses passivation. Besides describing the passivation process, Cody also explains the instances in which you should choose it for stainless steel parts and enclosures.

Watch the full video below – or, if you’d prefer to read Cody’s Proto Tech Tip, we’ve got the full transcription below.

Be sure to subscribe to Protocase’s YouTube channel so you don’t miss a single Proto Tech Tip!

Hey everybody, Cody here from Protocase with another Proto Tech Tip. This week, we’re going to talk a little bit about passivation on a stainless steel parts and enclosures. Passivation is the process of treating stainless steel with citric acid in order to remove free iron from the metal surface.

When the surface iron is removed, a passive surface film comprised of chromium nickel oxide is applied. Once the stainless steel is exposed to air, the chromium nickel oxides react with the oxygen to form an oxide layer protecting the rest of the steel from corrosion. So you may be wondering, why do we need a passivate stainless steel when it’s naturally corrosion resistant? Well, stainless steel can still oxidize due to the inherent properties of the metal, so passivation is essentially maximizing your corrosion resistance.

If your design is a stainless steel part or enclosure that you don’t want to have painted, passivation is a wise choice. Same goes for if you’re choosing a bare metal finish such as grained finish or a number four finish. We would still passivate your parts after they have been brushed. However if you choose to have your stainless steel parts powdercoated, passivation is typically not required. This is because once the powdercoat is applied, the stainless steel will not corrode, but if you are masking certain areas of your stainless steel parts for electrical conductivity or any other reasons, I would recommend requesting the masked areas to be passivated so that they do not oxidize.

We complete passivation in-house here at Protocase using our passivation tanks. Keep in mind that the parts cannot exceed the size of our tank which is 43.5″ long, 30.5″ wide and 30″ high. During the passivation process, your parts will be hung by stainless steel hook and placed inside of the passivation tanks. Our process consists of six different stages. The first tank is a simple dip into a degreasing solution, the second and third tanks are a simple rinse cycle. The fourth tank is where all the magic happens. It’s dipped inside of a tank which contains a coarse oil solution. Stage 5 is another simple rinse cycle, while the sixth and final stage is where the parts are dried off in an oven for 10 to 15 minutes.

One final thing to note is that, over time, your stainless steel parts that have been passivated may have the appearance of rust on them. Don’t worry though, these are just small deposits they can be wiped off using vinegar on a lint-free non abrasive cloth.

So I hope you found this week’s tip to be helpful and gain a better understanding as to why we recommend your stainless steel parts or enclosures to be passivated. In the end, it will
greatly increase the corrosion resistant properties of your parts.

Thanks for watching everybody and we’ll see you next week on another Proto Tech Tip!