Nanofluids are engineered colloidal suspensions of nanoparticles in ordinary base liquids that are of interest for cooling systems because of their enhanced transport properties, especially thermal ones, as compared to those of the base fluids. However, the interactions (i.e., erosion and nanoparticle deposition) of such nanofluids with cooling-system materials are largely unknown. Single- and multiple-impact erosion standard tests that may apply to nanofluids are presented and discussed. The authors designed an erosion-test instrument that allows testing of nanofluid erosion on material test specimens for typical cooling-system operating conditions. Experimental work is presented of wear and erosion effects on copper and aluminum specimens when impacted by suspensions of alumina nanoparticles in coolant fluids (i.e., for weight concentrations of 2 % and 5 % of nanopowders in distilled water, and in solutions of ethylene glycol in water). The possible material surface changes are assessed as comparative roughness measurements. This investigation sets a baseline for further research and provides recommendations for testing of erosion by nanofluids.