Passivation Process: Explained

What is Passivation? Passivation is the act of making materials such as stainless steel, aluminum, silicon or other ferrous materials to a “passive” state. When these materials become passive they can much more easily resist elements like water and air.

Still confused?
In passivation a small micro-coating is applied to the material as a source of protection against degradation. This process often involves applying a layer of metal oxide to the metal.

Passivation is very comment today especially in Silicon applications. Various forms of metal passivation are often found in computers, cell phones, and tablets.

Passivating Stainless Steel

Many people believe that, given the name “stainless steel” the material is guaranteed to be 100% protected from deterioration and corrosion.

This in fact is not the case.

Stainless steel is made to varying grades of durability. While some are extremely strong and will not be affected by adversely by “roughing”. Some specific grades of stainless steel are susceptible to being affected by tiny particles that can eventually become oxidized by water which we all know leads to the all mighty dreaded rust.

Passivation while an excellent option for increasing the lifespan of your stainless steel equipment. It can also be dangerous if companies misrepresent the integrity of the passivating stainless steel process. The Industry currently has the ASTM A 967 and AMS 2700 standard to help maintain consistency in the passivation process.

Aluminium Passivation

Aluminium as many of us know includes a layer naturally to help protect from rust damage. Aluminium alloys are a different beast entirely with very little natural oxidation protection.

Passivating various Aluminium alloys is obviously very beneficial in holding back rust and other external damaging factors. Most often a tiny layer is added to the aluminium to provide the protection.

Their are three main types of passivation when it comes to aluminium:

Alclad – is a corrosion-resistant aluminium sheet formed from high-purity aluminium surface layers metallurgically bonded to high-strength aluminium alloy core material.

Chromate conversion coating
– is a type of conversion coating used to passivate aluminum, zinc, cadmium, copper, silver, magnesium, and tin alloys.

Anodizing – is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts.

Citric Passivation Treatment

Nitric acid has been the most popular passivation treatment for the better part of a century. Recent developments in the study of passivation however have led to the introduction of citric passivation treatment. The most obvious difference between Nitric and Citric passivation is the safety. Nitric acid requires hazardous handling by trained professionals while citric is generally safe for any situation.

Safety is not the only positive factor when considering citric passivation. The majority of companies also have documented significant cost saving year over year.

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