Investigation into the Effect of Dissimilar Metal Coupling,Potential,and Processing on the Mode and Distribution of Galvanic Corrosion Attack on 5086Aluminum Alloy in Synthetic Seawater.

摘要

The galvanic corrosion behavior of 5086 aluminum alloy in three tempers (H116, H117, H32) when coupled with three more noble metals (1040 steel, 60/40 naval brass, Ti-150A titanium) and immersed in aerated synthetic seawater has been characterized. In so doing, use was made of potentio-dynamic polarization techniques, galvanic current density monitoring for twenty-four hours, and optical and scanning electron microscopic observations. The results obtained through the use of these techniques are presented and discussed. Galvanic corrosion of 5086 Al when coupled to the dissimilar metals was found to be independent of temper and to decrease in the order (of coupled metals) Ti-150A greater than 60/40 naval brass greater than 1040 steel. The effect of dissimilar metal coupling was found to be reduced by the formation on the anode and cathode of insulating corrosion product structures; this also caused an increased domination of the attack by localized corrosion modes. The effect of edges and crevices in concentrating attack and the correlation between distribution of corrosion product and metal dissolution is discussed. (Author)