Sliding mechanical components, used in the production and delivery of hydrogen, such as rings and pistons used in reciprocating compressors for point-of-delivery or industrial applications, can be subject to wear and parasitic frictional losses. Experiments were undertaken to assess the friction and wear properties of five high-performance polymers (PEEK, PI, PAI, PPS, and PTFE) sliding against steel and a DLC coating. Test results are presented for medium-speed sliding (3.5 m/s) in pure hydrogen gas or air, for 10 km distance using a horizontal cylinder sliding geometry. Coefficients of friction as a function of distance are graphed, and wear rates are...