Stainless steel is the alloy of choice in breweries, medical device manufacturing, food and beverage producers, and other industries. Manufacturers appreciate its strength and corrosion resistance. Stainless steel is an iron-based alloy with some carbon thrown in to create steel and a minimum of 10% chromium. Chromium contributes to its corrosion-resistant surface. The more significant the portion of chromium to iron, the more resistant to corrosion the surface will be.
It is important to note that a very thin surface layer of stainless steel protects the product from corrosion and rust. Although chromium-rich alloys are naturally passive (corrosion resistant), the product may become scratched or worn through time and use, removing the protective surface and leaving it vulnerable to corrosion. Therefore, it is essential to enhance this passive layer.
A Step Back in Time
Thankfully, in the mid-1800s, a chemist named Christian Freidrich Schönbein dipped some iron in concentrated nitric acid. Afterward, the iron, which normally would have easily rusted and corroded, had little or no reactivity. He called this “passive.”
Benefits of Passivation
Post-fabrication, passivation is a best practice for newly machined stainless-steel parts and components. Benefits Include
- Removal of contamination from the product surface
- Chemical film barrier against rust
- Reduced need for maintenance.
- Extended life of the product
This was a significant advancement, but there was a problem.
Nitric acid is a powerful oxidizing agent and a corrosive acid. Handling it comes with a significant risk of chemical burns. It quickly decomposes living tissue such as skin and flesh and is one of the most common types of acid used in acid attacks.
Other risks include yellow stains on human skin due to its reaction with the keratin. These stains turn orange when neutralized. Safety and disposal issues made using nitric acid for passivation difficult.
Adolf Coors Brewing Company was using stainless steel kegs for their beer, but the first time each keg was used, the beer had a metallic taste due to insufficient passivation. Subsequent kegs were fine, but that first one was a total loss. So, they began to experiment with different chemicals to passivate their kegs more effectively. Citric Acid was the clear winner! And it was safer for the consumer.
Integrated Technology for Your Passivation Needs
Integrated Technology specializes in handling small complex delicate parts. Our quick turnaround on passivation is unmatched in our industry.
When Quality Counts
You can count on Integrated Technology!