PREFERENTIAL WELD CORROSION-2

There is a range of methods for testing the corrosion of property of weld and their sensitivity to preferential weld corrosion and these were reviewed by Griffiths and others(1999).These tests were generally designed to be conducted in a laboratory on a sample weld to provide confidence in the welding procedures. However in practice a welder may deviate from the specified welding procedure and produce a poor quality weld. There is a need for non-destructive techniques good for identifying a weld that is susceptible to preferential weld corrosion after fabrication .
The scanning reference electrode technique has been used to assess the preferential corrosion of weldment for use in offshore applications when freely corroding and with applied potentials. The technique was found to be sensitive and reliable compared to immersion and potentiostatic anodic dissolution tests. The results of the test were used to develop two indices for assessing susceptibility to preferential corrosion,the first index(R1) was calculated from the hardness of the  HAZ parent plate and the highest hardness of martensite that the parent form.The second index (ChE) used the copper ,nickel and silicon content of weld metal and parent plate to assess their relative nobilities.