engleski

Pitting liability testing and the risk of technical failures

The relation between pitting liability determined by laboratory testing and the risk of failures in technical systems is analysed. Many technical failures are caused by pitting corrosion of structural metals (especially of stainless steels, nickel alloys, aluminum and its alloys). Such failures manifest themselves mostly as perforations of thin-walled structures (pipes, vessels and other hollow objects) or as cracks and fractures at the bottom of pits on structures under stress. On the other hand, pitting liability is usually estimated on the basis of tests concerning the behaviour of specimens exposed to a particular electrolyte. If pitting appears the number of pits (np), their depths (hp) and size (orifice areas, Sp) are determined. For the evaluation of pitting failure risk important quantities are: ľ maximum pit depth (hmax) and ľ pits density ie number of pits per unit area (np/S). The greater value of hmax corresponds to the shorter time before the first failure. The increase of np/S provokes the probability of frequent subsequent failures. The reliability of failures forecasts is also discussed.

pitting corrosion; stainless steels; failure risk; pitting liability

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