The following types of corrosion can occur in Stainless Steels:
- Gernal Corrosion
- Pitting
- Crevice Corrosion
- Stress Corrosion Cracking
Pitting is a form of local corrosion producing attacks of limited area but often to a considerable depth. It occurs in stainless steels in neutral or acid solutions containing halides, particulary chlorides, bromides and iodides. These ions break down the protective passive film locally, at points where it is weakened, for example, by non-metallic inclusions (slag) or by damage resulting from machining or use.
Crevice Corrosion occurs in crevices and other narrow spaces. A crevice can occur as a result of unsuitable design or material defects. If the crevices can be avoided, then crevice corrosion can be avoided, therefore Kent Stainless pay special attention to design and manufacture and suitable measures are taken when products are being installed as to avoid crevices from occurring.
Stress Corrosion Cracking results from the combined action of three factors:
- Tensile stresses
- A corrosive medium
- Elevated temperature
Similar to pitting in initial stages but it then develops into cracks. In certain cases a virtually brittle failure at the stress far below the tensile strength of the material.
The austentic range of stainless steels are highly durable and have a high resistance to corrosion attack. By adding chromium as an alloy to the steel, a passivating oxide layer is formed, with a high content of chromium oxide. This oxide layer protects the steel surface against the oxygen in air and water. Stainless steel has the ability to automatically re-establish the chromium oxide layer, if the steel surface is bared. This restoration of the oxide layer will only take place, if the steel surface is completely clean and free of temper, welding slag and contamination from tools of ordinary mild steel. If this contamination of the surface is not removed, the steel may corrode.
To prevent this, the steel surface should be cleaned after welding and maching. Pickling of the stainless steel can do this. The pickling effectively removes all impurities from the surface of the steel, and allows re-establishment of a strong, uniform chromium oxide layer. The pickling solution consists of 0.5-5 volume % Hydrofluoric acid and 8-20 volume % nitric acid at a temperature of 25-60 degrees. The acid solution removes existing chromium oxide layer and any iron contamination leaving a pure steel surface, which subsequently rinsed in water reforms a strong chromium oxide layer.
Kent Stainless pay special attention to design and manufacture and after fabrication all Kent Stainless products are pickled to ensure corrosion does not occur in any of our products, ensuring a long and maintenance free working life. | 
