Investigating the impact of post-weld cleaning and passivation on the performance of austenitic stainless steel using an EIS paste-electrolyte cell

The study investigates the impact of mechanical cleaning, citric acid+sodium hydroxide (CA), and nitric acid (NA) passivation on welded SS304 stainless steel plates, taking into consideration surface roughness. An innovative EIS paste–based cell is employed for this purpose. Welded systems in both the heat-affected (HAZ) zone and base metal (BM) are being analyzed before and after each treatment. Specifically, one welded plate underwent mechanical cleaning, another was solely subjected to CA passivation, and a third received both mechanical cleaning and CA passivation. Aging tests were conducted in a condensation chamber to confirm the effectiveness of cleaning and passivation treatments. Regarding open-circuit potential (OCP), most samples remained within the passive region, except for the mechanically cleaned heat-affected zone and the intentionally abraded surface immediately after abrasion. Rp values, which are in line with the OCP measurements, range from 104 to 107 Ω cm2 for all the observed samples. As the degree of abrasion on the NA-passivated surface increases, the electrochemical impedance spectroscopy (EIS) spectrum shifts from that characteristic of the passive towards that characteristic of the active state of the stainless steel.