Pitting corrosion studies on SS316L wall fabricated by directed energy deposition based wire arc process

Abstract

This study investigates the pitting corrosion behavior of SS316L walls fabricated using the Cold Metal Transfer (CMT)-based Directed Energy Deposition (DED) process. Corrosion testing was conducted by immersing specimens in a chloride-rich ferric chloride solution at 50°C for different durations (24, 48, and 72 h). The results demonstrated a progressive increase in pitting severity, with weight loss increasing from 0.1520 g at 24 h to 0.4620 g at 72 h, highlighting significant localized material degradation. SEM analysis revealed that pit diameters increased from approximately 30.2 μm after 24 h to 42.0 μm after 72 h, confirming the breakdown of the passive Cr₂O₃ layer and intensified metal dissolution. The calculated corrosion rate escalated from 0.80 mm/year at 24 h to 2.40 mm/year at 72 h, indicating an accelerating corrosion mechanism with prolonged exposure. Pitting corrosion density, quantified through SEM image analysis, increased from 120 pits/cm² at 24 h to 250 pits/cm² at 72 h, showing the continuous formation and deepening of pits over time. EDS analysis confirmed localized depletion of chromium and molybdenum, with elevated oxygen and chloride concentrations within pits, verifying the aggressive localized attack. These findings underscore the susceptibility of CMT-DED SS316L to pitting corrosion in chloride environments, emphasizing the need for optimized post-processing techniques such as annealing, passivation, and surface coatings to enhance corrosion resistance for industrial applications.