Corrosion performance of ER70S-6 steel produced by Additive Manufacturing process using wire-feed metal arc welding

Additive Manufacturing (AM) is a promising technology for the production of complex components with reduced weight in a relatively short time. Although the focus in recent years was mainly attributed to AM processes using powder bed technology such as SLM (Selective Laser Melting) and EBM (Electron Beam Melting), those processes are still considered relatively expenses due to the high cost of powder handling. The present study aims at evaluating the corrosion behavior of low carbon steel components produced by an innovative AM process known as WAAM (wire arc additive manufacturing) were the expensive powder handling is substituted by regular wire-feed metal. The motivation for this study was generated due to the modified microstructure produced by WAAM that can damage the corrosion performance of the printed alloy. Test samples in the form of cylindrical rods were produced by WAAM process using ER70S-6 wires and compared with its counterpart wrought steel (ST-37). The corrosion resistance was evaluated by salt spray testing, immersion test, and potentiodynamic polarization analysis while stress corrosion behavior was examined, by slow strain rate testing (SSRT), all in 3.5% NaCl solution at ambient temperature. The microstructure and phase assessment were evaluated by scanning electron microscopy and X-ray diffraction analysis. The results obtained revealed that although the corrosion resistance of WAAM samples were quite similar to that of the counterpart wrought steel (ST-37) the relative time to failure of WAAM samples under stress corrosion conditions were significantly increased. This was related to the relatively higher solidification rate of WAAM samples that consequently encountered increased internal stresses and reduced amounts of pearlite phase which altogether have modified the stress corrosion mechanism of the counterpart alloy.