SULFIDATION, DOWN-TIME CORROSION AND CORROSION-ASSISTED CRACKING ON HIGH-ALLOY MATERIALS IN SYNTHETIC COAL GASIFIER ENVIRONMENTS

At the KEMA laboratories, three types of corrosion concerning heat exc hangers in coal gasifiers were studied in detail: (1) resistance of ma terials to general corrosion (sulfidation); (2) down-time corrosion; a nd (3) interaction between stress/strain and corrosion (corrosion-assi sted cracking). A combination of optical and scanning electron microsc opy and special sample preparation techniques gave excellent informati on about the corrosion mechanisms of sulfidation and down-time corrosi on. The slow strain rate testing technique was applied to classify mat erials according to resistance to corrosion-assisted cracking. Critica l temperatures for cracking were determined.