Many industrial applications use stainless steel because it can resist corrosion and withstand a high degree of wear and tear. Stainless steel owes a lot of its valuable traits to passivation, a chemical process during which acids remove excess iron from the material’s surface, resulting in an inert oxide layer that protects the steel from rusting.
Many manufacturing and industrial organizations, including ASTM, ASME, SAE, SEMI, and the FDA, have implemented strict stipulations governing the proper passivation of stainless steel. Because stainless steel goes on to form a critical element of many construction, manufacturing, transportation, and food processing applications, passivating steel within regulations is paramount to creating reliable products.
But what is passivation, and why is it so important?
Understanding the Passivation Process and Its Benefits
Passivation is the process by which workers make metal surfaces “passive,” or more immune to corrosive elements they may encounter. This chemical treatment increases the corrosion resistance properties of a wide variety of metals, metalloids, and metal alloys such as:
- Steel
- Aluminum
- Copper
How Does It Work?
Workers usually use chromium to passivate metal alloys because it resists corrosion very well. After immersing metal components in an acid bath of either nitric or citric acid, chromium binds with oxygen to create a chemically inert passive layer or thin film on metal surfaces. This thin film prevents the kinds of chemical reactions that result in rusting or corrosion.
Benefits of Passivation
Passivation brings four main benefits to metals:
- Increases corrosion resistance
- Removes surface contamination left over from milling processes
- Reduces the risk of product contamination
- Increases term length between maintenance intervals
Passivation of Stainless Steel: Why Do It?
Stainless steel alloys are comprised of iron, nickel, and chromium in varying ratios of each element, and these ratios determine the steel’s grade. In cases that require the steel to resist extreme temperatures or excess levels of corrosive agents, steelworkers add molybdenum to the chromium to enhance its protective properties.
Stainless steel components undergo the same acid bath treatment as described above, which creates a passive surface that prevents iron from reacting with oxygen to create rust.
After the machining process, stainless steel components frequently have free iron left over that risks contaminating the workpiece. Passivation cleans away these contaminants and creates the necessary passive layer that makes stainless steel so versatile. By employing good passivation practices, businesses can make their products perform well in a variety of different applications.
High-Quality Steel Solutions at Durco Manufacturing
Durco Manufacturing provides these services and seeks to meet and exceed the passivation standards set for each stainless steel application.
On top of our full suite of stainless steel passivation services, we also work with other important industrial metals like aluminum and copper. Contact us today to learn more about our passivation processes and how they’ll benefit your next project.