Steel has a tendency to rust and corrode, which can cause problems when stainless steel is used for parts or components in machinery that’s used in damp environments. Fortunately, there are techniques that welders can use to help prevent rusting. Weld passivation is one such technique that’s taught in welding training programs, and that can extend the service life of stainless steel components.
How do Welders Stop Metal from Rusting?
Stainless steel is an alloy made up of iron, nickel and chromium. It’s popular for construction and for making hardwearing parts because the chromium in the alloy makes it corrosion-resistant. However, iron rusts easily, and if there’s free iron on the surface of a stainless steel part, this will eventually corrode.
Welders can treat stainless steel to reduce the risk of rust and corrosion by using a process called weld passivation. Weld passivation doesn’t completely stop rust, but it can greatly slow down the process, thereby extending the lifespan of the parts or components in question.
How Does Weld Passivation Work?
Weld passivation is a process of using nitric or citric acid to remove free iron from the surface of the part, leaving behind a more uniform surface that has a significantly higher percentage of chromium on it. This “passivation layer” of oxides on the surface is less prone to reacting with the air and, therefore, less likely to form rust. The part itself is stainless steel, and if it becomes scratched or damaged, the underlying part will still rust, but the oxide layer forms a protective surface that is corrosion-resistant.
To ensure the success of weld passivation, the stainless steel parts must be:
- Free from dirt or other contaminants
- Pure stainless steel
- Relatively smooth and uniform (no cuts or pieces of iron embedded in the surface from cutting or grinding)
Leftover grinding swarf or particles of iron may hamper the formation of an oxide layer. It’s important to clean parts down to the grain, removing any debris, to allow a smooth and uniform oxide layer to form.
In addition, steel that has been treated with sulphides for better machinability isn’t suitable for weld passivation.
How do You Become a Welder?
The welding training course at the Environmental Technical Institute (ETI) provides in-depth training in the skills required to undertake a variety of welding jobs. Our comprehensive program covers health and safety, welding techniques and best practices, and more. Students will also spend time getting hands-on experience, so they’re ready to take on real-world welding jobs as soon as they graduate.
If you’re interested in starting work as a welder, explore the ETI welding program today. Our extensive training program covers everything you need to get started in this in-demand profession.
Key Takeaways
What is weld passivation?
Weld passivation is a process used on stainless steel to remove free iron from the surface, creating a protective oxide layer that helps resist rust and corrosion.
Why is weld passivation important?
It helps extend the lifespan of stainless steel parts by reducing corrosion, especially in environments where moisture and rust are concerns.
What is required for successful weld passivation?
The stainless steel surface must be clean, free of contaminants and iron particles, and relatively smooth to allow a uniform protective oxide layer to form.
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