A high-performance commercial alumina-forming Ni-base alloy was studied after a two years field exposure at 540degreesC in a methanol plant. Comparative laboratory studies were performed at 650degreesC using a different synthesis gas mixture with the composition; 50%CO + 3%H2O + 47H(2). Post exposure metallographic examinations with LOM, FEG-SEM, SEMEDX analysis as well as thermodynamic calculations were made in order to identify and describe the metal dusting mechanisms. An estimate of the metal dusting corrosion rates was per-formed based on metallography and these were correlated to a theoretical model based on diffusion processes.