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5. Intergranular Corrosion - all austentic stainless steels contain a small amount of carbon. At extremely high temperature, such as welding, the carbon forces local chrome to form chromium carbide around it, thus starving adjacent areas of the chrome it needs for its own corrosion protection. When welding, it is recommended you consider low carbon stainless such as 304L or 316L. 6. Selective Leaching - Fluids will remove metal during a de-ionization or de-mineralization process. This usually happens inside a pipe and is rarely a fastener problem. 7. Erosion Corrosion - This corrosion happens when the velocity of an abrasive fluid removes the passivation from a stainless. Again, this is almost exclusively limited to pipe interiors and rarely a fastener problem. 8. Stress Corrosion - Also called stress corrosion cracking or chloride stress corrosion. Chlorides are probably the single biggest enemy of stainless steel. Next to water, chloride is the most common chemical found in nature. In most environments, the PPM are so small the effects on stainless are minute. But in extreme environments, such as indoor swimming pools, the effects can be extreme and potentially dangerous. If a stainless part is under tensile stress, the pitting mentioned above will deepen, and cracking may take place. If you are using stainless steel bolts under tensile stress, in an environment where chlorine corrosion is likely, you should examine the potential for stress corrosion cracking carefully. According to a NACE International & CC Technologies study, corrosion costs the United States $276,000,000,000 annually. That's $276 billion and 4.2% of the nations GNP. In the power generation and transmission industry alone, it is estimated that nearly 8% of the typical electric bill is attributed to the cost of corrosion. It is unknown how many lives are lost annually due to corrosion but the number could be frighteningly high. Extreme examples thru the years include collapsed bridges and jet airliner crashes. Summary No metal, except for gold and platinum in their natural state, are completely corrosion proof. But stainless steel has proven in thousands of applications, that it is one of the most economical solution's to combat the ever present elements that cause corrosion.
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