Abstract
A corrosion survey of the buried structures in a "pilot" area in the western coast of the Arabian Gulf showed that, in less than ten years of construction, metallic structures such as galvanized steel, ductile iron, cast iron and carbon steel with thin bituminous coating exhibited severe general corrosion and pitting. In order to substantiate the survey results, coupons made of mild steel, cast iron, galvanized cast iron, copper, brass and stainless steel were installed in three locations and kept buried for over three years. Coupons were retrieved after 435 days and 1,165 days of burial and corrosion of the coupons was determined by the gravimetric weight loss method. The results showed that exposure Site 16 has the most corrosive soil. The cast iron, mild steel, and galvanized cast iron coupons experienced severe corrosion at the three burial sites. The corrosion rates of these materials in burial Site 16 were 13.4, 9.2 and 7.1 mpy (340, 234 and 180 μm/y) respectively, after 1,165 days of exposure.
The cast iron coupons corroded by severe graphitization covering 30-90% of the exposed surface and severe pitting 5-37 mils (127-940 μm) deep. The mild steel coupons suffered severe general corrosion and pitting, with pits as deep as 50 mils (1270 μm). The galvanized cast iron coupons also had severe corrosion and pitting. Pitting was severe, especially at the edges, and the pit depths ranged between 10 and 50 mils (254 and 1270 μm). The brass and copper coupons showed only mild corrosion. The stainless steel coupons were the best performers among the materials tested. They did not have any measurable corrosion.
