Why is electro-polishing stainless steel important?

Using stainless steel for indoor use is ideal because of its strength, durability and naturally corrosion resistant form. In outdoor areas, stainless steel enjoys a strong and enduring reputation for visual appeal and structural integrity.

However, in areas that are high in salt or chlorine, those factors often cause “tea staining” to appear on stainless steel. Tea staining is a discolouration of the surface of stainless steel by corrosion. Tea staining occurs most commonly near an ocean, river or near a swimming pool.

Electro-polishing is extremely effective in preventing surface contamination such as tea staining. In certain circumstances it will remove early stage tea staining. It also brightens and slightly smooths the surface. This enhances the protective passive oxide layer of the stainless steel by making it thicker which makes it more resistant to the harsher environments encountered outdoors, especially in Western Australia.

Corrosion resistance is not the only advantage that is improved when electro-polishing stainless steel. An electro-polished surface also repairs surface finish, makes the material easier to clean, and gives the material a striking finish.

Whatever use you have in mind for your stainless steel product, electro-polishing will enhance the qualities of this already versatile and popular material.

We at Civil and General Distributors can arrange for electro-polishing to be completed on all our stainless steel products before installation to suit your requirements.

THE BASIC SCIENCE BEHIND IT ALL

All stainless steels are iron-based alloys with a minimum of 50% iron and at least 10.5% chromium. The chromium content is the key to stainless steel’s basic corrosion resistance.

When chromium is exposed to oxygen, it spontaneously forms a passive oxide layer. This passive oxide layer is very thin, yet it prevents further diffusion of oxygen into the base material and thus prevents corrosion.

Corrosion resistance is increased further by;

• increasing the chromium content to levels above 11% (304 grade has 18% and 316 grade has 16%);
• the addition of 8% or higher amounts of nickel (both 304 and 316 grade have 8%); and
• the addition of molybdenum which also improves resistance to pitting corrosion (316 grade has 2%).

Electropolishing provides further protection by removing material from the surface of the stainless steel using an electrical current (rather than chemicals) which thickens the protective passive oxide layer.