Corrosion of the weld

Knife-edge corrosion

Due to high temperature of welding or unreasonably high temperature heat treatment, chromium carbides are concentrated at the grain boundaries of stainless steel. This leads to the oxidation of chromium at the grain boundaries, creating a galvanic couple compared to the base material and the weld corrosion in aggressive environments. Alloys with low carbon content or with additives of titanium and niobium (alloys 321 and 347) can eliminate this effect, but under the condition of high temperature processing after welding to prevent corrosion of knife. The name itself indicates that the zone of corrosion is limited. Often it is only a few microns in diameter. Such narrow slits hinder the access of oxygen, which is essential for the formation of a protective oxide film, leading to accelerated corrosion. Area knife corrosion is usually located near the weld and almost invisible.

Modern metallurgy largely avoids these problems by reducing the percentage of carbon in stainless steels below 0.3%. Such steels are referred to as L-varieties, for example, 316L. Most modern stainless steels are smelted with a low carbon content.

To buy, price

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