| Popis: |
A new test method for detection the susceptibility of stainless steel to crevice corrosion has been investigated in natural and biosynthetic seawaters. There is a general agreement that the main corrosion risk in practical application of passive alloys in the seawater and chloride solutions is the crevice corrosion. Therefore any qualification test should be the crevice corrosion test. The actually applied measuring methods are mainly of a comparative nature, aimed at ranking alloys related to the environmental use There is a lack of methods which can provide exact information about expected performance of alloys for a long term use. Our Institute in Dubrovnik participated in the development of a new test performed by the research group Marine Corrosion Working Party of the European Federation of Corrosion. We have taken into account the geometry of the crevice model, gasket materials, applied torque, finishing surface, and the potential increase rate.The monitoring of the free corrosion potential of two austenitic steels and a duplex steel, in the constant flowing conditions, as well as the redox potential, the temperature, chloride and oxygen contents, has been carried out in the natural seawater.In the synthetic seawater the organic component was simulated by glucose and glucose oxidase. Sharp drop of the corrosion potential was used as an indication of the crevice corrsion initiation.After exposure crevice formers were removed for the visual and microscopic inspection on the crevice area on specimens |
