Corrosion of welds between composite tube alloys in simulated recovery boiler environments

Corrosion of butt welds joining dissimilar alloy composite tubes has been a common observation in kraft recovery boilers. This damage has been ascribed to different mechanisms. Dilution of the chromium content in the weld beads has been put forward as the most likely cause, but there has also been much speculation about " galvanic" corrosion between the two dissimilar alloys. In an effort to better understand whether galvanic corrosion was a factor, test coupons were fabricated from a variety of weldments, galvanically coupled, and exposed in the laboratory to a liquid environment thought to cause corrosion in recovery boilers.