Passivation

Precision Finishing for Unparalleled Shine, Durability, and Corrosion Resistance

What Is Passivation

Passivation is the removal of free iron from the surface of stainless steel. The acid treatment dissolves the free iron and facilitates the formation of a thin, transparent corrosion resistant oxide layer.
When the surface iron is removed, the other components of the alloy (primarily chromium, often nickel as well) are left behind as a surface layer over the underlying steel. Upon exposure to air, these elements react with oxygen to form an oxide layer that protects the rest of the steel from corrosion.

This corrosion-resistant surface can be damaged through mechanical means or heat or chemical damage. When that happens, iron is exposed and the item is once again subject to rusting.

How It's Done

Passivation is done by immersing the part in a solution at a controlled temperature.

Benefits

Passivation is another chemical process that creates an oxide layer to protect stainless steel surfaces against rust and corrosion. Stainless steel’s most vulnerable points of corrosion lie in its grain boundaries, where iron deposits tend to settle during the manufacturing process. Passivation in an acidic compound helps to smooth out those boundaries, releasing some of the iron that can later cause rust.

What Is Rust

Rust is a natural chemical process in which an anode (such as a metal surface) comes into contact with an electrolyte (a liquid, such as water) and a cathode (such as another metal surface).

The iron particles within the steel and the steel itself rapidly trade electrons when water is introduced. With so many electrons in motion, some of the metal surface is lost. Rust is effectively the disintegration of metallic objects. The tell-tale reddish-brown color is what the chemical process leaves behind.
Some conditions that will cause stainless steel to rust include:

Oxygen

Oxygen is, of course, a natural oxidizer – a key element in the rusting process. Iron naturally combines with oxygen, causing the rusting process.

Water

Any stainless steel used in water is particularly susceptible to rust and corrosion. This is especially true in the ocean.

Humidity

Moisture in the air, i.e. humidity, acts on the iron in stainless steel in the exact same way submerging it in water does.

Ocean Breeze

Humidity in the ocean air carries particles of salt along with it, and accelerates rusts and corrosion in stainless ste

Rain

As rain falls, it carries air pollution down with it. The make-up of a single raindrop over an industrial area is a soup of corrosion-accelerating chemicals.

Electricity

Adding a few extra volts of electrical current to the metal only makes it that much easier for those pesky electrons to escape, carrying metal material with it.