Stainless Steel Passivation Process

Passivation for Stainless Steel

What is Passivation?

Passivation is the process of removing iron from the stainless steel surface and encouraging the formation of a passive protective film. Passivation maximises the corrosion resistance of stainless steel, helping it to stay rust-free for much longer.

Although stainless steel is naturally corrosion-resistant, the process of passivation ensures maximum protection from any rust that could otherwise form.

Why Passivation?

Passivation is essential for all grades of stainless steel. Passivation promotes the natural formation of a protective layer on the stainless steel, protecting the surface from contamination.
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Without passivation, iron in stainless steel is easily exposed to pollutants that cause corrosion, and eventually, rust. Any stainless surface is vulnerable to rust over time, so it is essential to ensure every part of the stainless steel is covered during the passivation process.

The Passivation Process

Passivation involves first a thorough cleaning and degreasing of the steel. This process removes any organic or metallic residue left over from the fabrication process.

After cleaning, the parts are then submerged in a passivation solution. The concentration of the solution, the temperature, and the time the steel is left in the bath are all dependant on the type and grade of stainless steel. These variables are to be correctly managed, as accuracy is vital in ensuring the best results.

Nitric acid and citric acid passivation

Although nitric acid-based products are the traditional choice for passivation, alternatives such as non-toxic citric acid quickly become more popular for their ease of use and biodegradable qualities.

A citric acid solution, such as CitriSurf is one of the most affordable stainless steel passivation methods. CitriSurf products work on most stainless steel grades and the solution does not need to be heated, unlike nitric acid. This takes much of the guess-work out of ensuring your stainless steel is adequately passivated.

Not only that, CitriSurf additionally provides a thicker corrosion-resistant layer than traditional nitric acid formulations, meaning stainless steel stays rust-free for longer.

CitriSurf Passivation

Reba Scientific provides a range of CitriSurf products, perfect for various residential, commercial, and industrial applications. As the CitriSurf passivation process is much more straightforward than traditional nitric acid passivation, almost anyone can perform it.

CitriSurf 2210

CitriSurf products include a gel solution for joints, welds, and other areas particularly vulnerable to corrosion and rust. Use the CitriSurf 2210 gel solution when you need to passivate on weld joints, vertical surfaces, and other large items or areas that cannot be conveniently dipped in a bath.
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CitriSurf 77

The CitriSurf 77 spray solution is suitable for applications where the stainless steel item is fixed or too large to bathe. It can also be used for tiny areas via either spraying or brushing on to the steel.

Our CitriSurf products are suitable for a wide array of applications. For instance CitriSurf 2450, for improved performance on sensitive grades of stainless steel, and CitriSurf 2250, for most steel grades, including austenitic, martensitic, ferritic, precipitation hardening, and duplex.

For safer stainless steel passivation,  CitriSurf is the answer, available from Reba Scientific.