Metal dusting problems experienced around one of the world's largest oxygen-blown secondary methane reformers in a gas-to-liquids synthetic fuel plant are reviewed. Practical plant exposure trials of various materials were conducted in the reformer inlet area, the waste heat boiler tubesheet in the gas inlet chamber, and the waste heat boiler by-
pass valve in the gas outlet chamber. Alloy UNS N08810 was found to greatly out-perform the high nickel alloy UNS N06600 in the reformer gas inlet stream but was found to be extremely vulnerable to metal dusting attack in the reformer gas outlet stream. Improved performance was experienced in the by-pass valve with 310 stainless steel which had been
treated by a proprietary process to diffuse aluminium into the surface, but the most resistant materials were found to be alloy UNS N06601 and 50/50 Cr-Ni. The latter material appeared to be immune to metal dusting attack after 17 months exposure. The waste heat boiler inlet tubesheet was also successfully protected from metal dusting attack by a thermal spray coating of 50/50 Cr-Ni. The high velocity oxy-fuel (HVOF) application process was found to achieve superior coating integrity to the arc spray process.