Evaluation of the susceptibility to pitting corrosion of structural steels, including steels with modified surface

摘要

Although the low alloy ferrite-pearlite and bainite-martensite steels mostly undergo the general corrosion, pitting corrosion occuring under certain conditions jeopardizes the safety of installations, causing perforation of walls or initiation of crack. On the basis of the electrochemical, corrosion and microscopic examinations, the conditions simulating typical industrial corrosion environments, containing the Cl- ions have been selected, to which the parts of machines, devices and installation are subjected. The test parameters provide the preferential pitting corrosion without prevailing general corrosion, and provide the similar type of corrosion of different kinds of ferrite-pearlite and bainite-martensite steels, including steels with modified surface layer. The proposed express method allows to evaluate the susceptibility of low alloy steels to pitting corrosion and to evaluate the effect of surface modification on susceptibility to pitting corrosion in environments containing Cl- ions. The method may be applied for the proper selection of materials exploited under pitting corrosion conditions and for preparation of precorroded samples for mechanical testing.