Effects of low-temperature duplex coatings on corrosion behavior of austempered ductile iron

This study utilized electroless nickel (EN) and cathodic arc evaporation (CAE) technologies, with the known advantage of low processing temperature (EN = 90 °C and CAE = 230 °C), to treat the austempered ductile iron (ADI) substrate. The eligibility of applying the EN and CAE–CrTiAlN duplex coatings on ADI, along with the coating properties, such as structure, roughness, and adhesion, were evaluated and analyzed. Moreover, polarization and immersion tests were performed to further understand the effects of the coatings on the corrosion resistance of ADI. The results showed that the unique microstructure of ADI did not deteriorate after EN and CAE treatments. With regard to corrosion resistance, the duplex coated specimens performed better than did the uncoated and monolithic EN or CrTiAlN coated ones in 3.5 wt.% NaCl and 10 vol.% H2SO4 aqueous solutions.