Corrosion Behaviour of High-Mn TWIP Steels with Electroless Ni-P Coating

Abstract

An attempt has been taken to improve the corrosion resistance of twinning-induced plasticity (TWIP) steels ) by electroless Ni-P coating. Corrosion resistance in 3.5% NaCl and 0.1M H 2 SO 4 solutions was characterized by the potentiodynamic polarization curves and Tafel method calculations. It was found that Ni-P coating improved the corrosion resistance by the factor of 4 and 40 in 3.5%NaCl and 0.1M H 2 SO 4 , respectively. Post-heat treatments, commonly used to increase hardness and wear resistance of Ni-P deposits, were found to reduce the corrosion resistance, even though the 1 h annealing at 700°C less than at 350°C. Also, the adhesion of the coating on the steels was impaired in annealing. The lowered corrosion resistance in annealing can be suggested to result from the crystallization of the amorphous coating and the formation of Ni 3 P particles, but at 700°C, the formation MnO layer on the top of the coating promoted the resistance by enhancing the passivation in the 3.5% NaCl solution.

Characterization and Comparative Analysis of Corrosion Resistance of 4 High Manganese Steels Models in Aqueous Solution of NaCl

“…The high manganese steels have, within their microstructure, the twins. These twins constitute modifications of the crystallographic orientation planes, improving their mechanical properties due to the mechanism of hardening by twinning 13 . The higher content of carbon improves the hardness due to the interstitial character of this element, which acts as a barrier to the discordance movement and that under special conditions helps the hardening by deformation, that is, the transformation of austenite into martensite as a response to deformation 3 .…”

Corrosion Mechanisms of High-Mn Twinning-Induced Plasticity (TWIP) Steels: A Critical Review

“…Fe−26Mn−0.14C alloy in 3.5 wt.% NaCl solution and of Fe−24Mn−3Al−0.1C alloy in 0.1M H 2 SO 4 solution was studied by Hamada and Karjalainen by applying electroless Ni−P coatings [74]. For the 26Mn alloy, an i corr of 28 µA cm −2 (324.8 µm year −1 ) and 6 µA cm −2 (69.6 µm year −1 ) for the uncoated and coated specimens, respectively.…”

“…%, yet the Ecorr and Epit decrease for Cr concentration up to 6.5 wt.% and due to κ-carbide (Fe,Mn,Cr)7C3 [101]. The alloy was aged using an anodic passivatio rent to promote a thick, protective passive film [74].…”

“…As-quenched, austenitic Fe−30Mn−9Al−(3,5,6.5,8)Cr−1C alloys in 3.5 wt.% NaCl solution showed passivation and lower E corr and E pit values as Cr content increased above 5 wt.%, yet the E corr and E pit decrease for Cr concentration up to 6.5 wt.% and 8 wt.% due to κ-carbide (Fe,Mn,Cr) 7 C 3 [101]. The alloy was aged using an anodic passivation current to promote a thick, protective passive film [74].…”

Effect of Thermo-Mechanical Processing on the Corrosion Behavior of Fe−30Mn−5Al−0.5C TWIP Steel

“…An increase in the electrochemical dissolution kinetics of TWIP steel has been observed in acid media due to the presence of alkaline Mn oxide (MnO) in the corrosion products. This increased anodic dissolution is attributed to the presence of Mn 2+ cations in solution, and the subsequent hydrogen evolution reaction (HER) on the cathodic half-cell electrochemical reaction [27].…”