THE PREFERENTIAL CORROSION -1

However,Bradley(1962) concluded that the silicon content of the weld had no direct effect on corrosion of steel wedments in sea water but had low hydrogen electrodes which would give rise to enhance corrosion of the weld.In such trend hicks,(1973) suggested the use of low alloy weld steels so that the weld is always cathodic to the base plate.Nevertheless,corrosion of the HAZ could still pose some problems for some application and will be dependent on the rate of cooling and Mn level in the steel,which affect the grain size and  the extent of the martensite formation.The net effect is that the HAZ could be anodic to the parent plate.Recent work at the welding institute (TWI) UK has shown the importance of nickel content in the weld metal compared to the parent plate with higher nickel content in the weld being percieved to result in the weld acting as a net cathodic with respect to adjacent parent plate. Macroscopic anodes and cathodes will develop only if there is sufficiently conducting medium, when the conducting medium is low or the medium is in the form of a thin liquid layer,the potential drop in the solution will be shorten, the distance over which anodes and carthodes can effectively interact.In those circumstances,significant localized corrosion can occur in regions that are percieved to be net cathodic,as has been observed