CORROSION OF MARIILOY~(TM), LOW CARBON - lCr STEEL PIPES, APPLIED TO CARGO OIL PIPES IN A VLCC AFTER TWELVE YEAR SERVICE

摘要

A low-alloy steel developed by Nippon Steel, MARILOY™ containing low-carbon and 1%Cr, was applied to cargo oil pipes without coatings in a VLCC (Very Large Crude Carrier). Inspection and investigation of the state of corrosion were conducted after 2.5-, 7.5- and 12.5-year service. The maximum pitting depth after 12.5 years was 5.0mm at the bottom of the pipes (initial thickness: 19mm). The inner side of the pipes was uniformly and tightly coated with sludge and corrosion products, it was estimated that the total life of MARILOY~(TM) cargo oil pipes studied in this paper should be at 30 years or more.