The most common grades used for flagpoles are 304 Grade (1.4301) and 316 Grade (1.4401). By adding Nickel and increasing chromium to 304 Grade, the internal structure of the metal is manipulated and the corrosion resistance increased. By further adding Molybdenum and increasing the nickel content to 10% 316 Grade is created and is more commonly known as "Marine Grade". This grade of steel is better suited for coastal or more heavily polluted environments.

Staining
One of the greatest misconceptions with stainless steel is that it will never stain or discolour. All stainless steel has a "passive" surface, a protective layer of chromium oxide, which minimises corrosion, but this passive layer can be attacked by certain chemical particles such as salts or industrial pollutants.

"Tea Staining" is quite common in lower grade stainless steel, such as 304, particularly close to the sea or in more polluted areas and near main roads. This brown discolouration, caused principally by salt deposited on the surface, does not affect the structural integrity or longevity and it can be controlled but it is unsightly.

We can offer clients 304 Grade, we will always recommend 316 Grade for our flagpoles. Experience has shown that 304 is adequate within inland sites where there is little to no atmospheric pollutants; wind exposure, industrial pollution and high temperatures can create an environment whereby 304 Grade will tea stain even when 20 kilometres from the sea.

We believe that the best way to minimise the risk of staining and to ensure you get the right stainless steel flagpole is to specify and insist on a 316 Grade flagpole.

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