PurposeThe purpose of this paper is to investigate the corrosion of the heat‐affected zone (HAZ) and weld zone of austenitic stainless steels that have been welded using two different processes. The corrosion behavior is evaluated in synthetic seawater using the electrochemical polarization technique.Design/methodology/approachWelded and unwelded UNS S30403 specimens were welded by flux core arc, and gas tungsten arc welding (GTAW) techniques. The test equipment consisted of an electrochemical three‐electrode cell using synthetic seawater as the corrosive medium. The scan rate was 10 mV/s and the potential range was −500‐500 mV vs saturated calomel electrode. The pH for the synthetic seawater was around seven. The electrochemical tests were performed after 1, 2, 3, and, 11 weeks. The metal surface was characterized by examination using an inverted microscope and scanning electron microscopy.FindingsThe polarization measurements of the flux core arc welding‐HAZ showed a high corrosion susceptibility, while GTAW‐HAZ presented good corrosion performance.Practical implicationsWith the application and correct interpretation of this electrochemical technique, designers, welding engineers, and manufactures can access important information and take correct decisions regarding welding processes to meet corrosion resistance requirements.Originality/valueThe methodology and approach of interpreting the polarization plots used in this research can be applied to study other welding techniques and different welded metals in specific corrosive media, which will be of value to the welding industry.