A2 Stainless Steel (Type 304) performs well on exposed surfaces although slight discolouration may occur on sheltered surfaces.
A2 Stainless Steel (Type 304) may suffer slight tarnishing.
A4 Stainless Steel (Type 316) performs well in typical urban atmospheres and suffers little if any, tarnishing.
A2 Stainless Steel (Type 304) will often suffer moderate to heavy attack although its performance can be improved by washing. For less extreme pollution this type may prove satisfactory, but for aggressive locations an upgrading is recommended.
A4 Stainless Steel (Type 316) will perform well in most industrial atmospheres. A light tarnish or staining can be kept to a minimum by regular washing.
A2 Stainless Steel (Type 304) will suffer quite severe pitting and should be considered with caution.
A4 Stainless Steel (Type 316) is the most suitable of the steels most commonly available, and will generally provide a good service even at shoreline sites. A pristine finish will be maintained with a regular wash to remove contaminants. If unwashed there will be a degree of discolouration on long exposure.
In circumstances where a marine atmosphere is combined with aggressive industrial pollution, Type 316 may suffer unacceptable attack. In such cases it may be necessary to consider a special highly alloyed grade.