Crevice corrosion

This type of corrosion occurs on metal parts on the presence of a corrosive medium in uncompleted edition columns as overlaps, pockets webs and not welded by welds. A distinction is made in the crevice between oxygen and hydrogen type. The driving force in both cases is the concentration difference between gap and outer gap region of the corrosive medium. The associated with the concentration difference potential difference causing electrochemical corrosion of the gap ( hydrogen type) or its direct environment ( oxygen type).

Even stainless CrNi steels can corrode in a column, if there is no oxygen to form the protective oxide layer present.

A corrosion resistant selection of the material of construction is initially the most economical way of corrosion prevention. Further crevice corrosion can be prevented by constructive dispensed to the column or it performs such that crevice corrosion is avoided. According to DIN EN 12502-4 " Protection of metallic materials - Influencing factors for stainless steels " are advised to carry out the gap widths greater than 0.5 mm in order to avoid crevice corrosion, but is out of the gap width and the gap depth of meaning. In addition, constructive inevitable gaps can be sealed with plastic; This principle is exploited in the connection of risk from corrosion bolts and nuts that are backed up by an appropriate adhesive to prevent unintentional loosening and protected against crevice corrosion.