Your customer should have provided the test duration requirement, since this is not a standard test in most Cr plating standards (ASTM B 177, ISO 12686, automotive OEM standards, etc.). The performance in such a test will depend on the quality on the coating, the thickness, and the type of deposit (conventional sulfate, mixed-catalyst, high-speed fluoride-free). A high-quality ~ 20 micrometer thick layer with no defects, plated using the high-speed fluoride-free (HEEF) process should be able to withstand at least 6 hours of CASS testing according to ASTM B 368 or ISO 4541.