Piping and other hardware in coal preparation plants are susceptible to degradation by dissolved salts and suspended coal in the process water. Because the coal mined underground in Appalachia and the Midwest is now increasing in chlorine content, there could be an adverse impact on materials performance. In-plant tests were conducted to determine the effect of chlorine concentration in process water on corrosion and erosion rates and to explore methods of corrosion control. The results showed an inverse dependence of corrosion rate on chloride ion content of the process water. Supplementary experiments conducted in the laboratory showed that the corrosion rate of 1018 steel goes through a maximum as a function of the chloride plus sulfate concentrations in water. Also in the plant tests, cupronickel alloys not considered previously for this application performed well, but metal wastage of the cupronickels was greater than for 304 stainless steel. Success was achieved in cathodically protecting two wear-resistant alloys in coal slurry piping (Hadfield(1) steel and high-Cr cast iron).