The effect of electroless Ni-P interlayer on corrosion behavior of TiN-coated austempered ductile iron

This study aims to investigate how austempered ductile iron (ADI) substrates, coated using electroless nickel (EN) and cathodic arc evaporation (CAE) surface technologies, can mitigate the corrosion problem. EN of different thickness was used as an interlayer for CAE-TiN coated ADI. Coating structure, roughness, and adhesion were measured to characterize the coating layers. Polarization tests were carried out to examine the effect of EN interlayer thickness on the corrosion behavior of TiN-ADI. As indicated in our results, the unique microstructure of ADI did not deteriorate after the EN and CAE treatments. Also, the duplex coated specimens had better performance than the monolithic TiN coated specimen in the corrosion resistance test with 3.5 wt.% NaCl aqueous solution. In particular, the TiN-ADI with a 25 mu m EN interlayer had the best corrosive protection. (C) 2012 Elsevier B.V. All rights reserved.