Thermal cycling life of plasma-sprayed alumina coating on cast irons has been performed in comparison with the alumina coating on steel. The samples were prepared by plasma-spraying alumina on flaky graphite cast iron and spheroidal graphite cast iron without an undercoat and with an undercoat of nickel based self-fluxing alloy or nickel-chromium alloy. Thermal cycling test revealed that the coating on flaky graphite cast iron shows a good thermal shock resistance and undercoating improves the property appreciably by preventing oxide formation on the substrate.