Two periods of in-plant exposures of candidate materials in the Westinghouse PDU have been completed. Coupons were exposed in the gasifier, hot-gas cyclone, quench scrubber, and gas cooler vessels. Corrosion monitoring of test materials is currently being conducted in the Westinghouse Coal Gasification Process Development Unit (PDU) coal gasification pilot plant. The corrosion data presented are from work during 1981 through 1984. During these two exposure periods, several coals ranging from lignites to bituminous coals and two petroleum cokes were gasified in the steam-oxygen mode. Fouling was observed on most corrosion racks. The effect of this process-related material was to promote corrosion. In the gasifier environment, alloys 6B, IN 671, and 18SR were the best performing alloys. Nickel-base alloys with Ni/Cr ratios >1.5, namely IN-617, IN-825, and alloy X, incurred severe corrosion attack in both exposures. Other alloys, although generally acceptable in corrosion performance, were not immune to solids-induced corrosion around coupon mounting holes. Several refractories such as Brickram 90, Harbison-Walker Ruby, and Chemal 85B showed little degradation in both gasifier exposures. Nitride bonded silicon carbon Refrax 20 had the greatest reduction in abrasion resistance as well as other properties. Single-phase structural ceramics including siliconized SiC, sintered ..cap alpha..-SiC, and Al/sub 2/O/sub 3/ did not suffer any noticeable damage. Materials evaluation in the hot-gas cyclone showed IN-671 and 26-1 to be more resistant than Type 310 and Type 310 aluminized. 18 refs., 23 figs., 24 tabs.