浓硫酸中304不锈钢焊接接头腐蚀行为的电化学研究

Electrochemical Studies on Corrosion Behaviors of 304 Stainless Steel Welded Joints in Concentrated Sulfuric Acid

为了给应用于浓硫酸工业生产的304不锈钢管道的防护提供指导,采用电化学阻抗谱法与动电位扫描法研究了304不锈钢焊接接头各个区域在质量分数为98%的浓硫酸中不同温度下的腐蚀行为。结果表明:304不锈钢焊接接头在浓硫酸中的腐蚀形式以点蚀为主。在相同条件的浓硫酸介质中,焊接接头各区域耐蚀性优劣依次为:基材、焊缝、热影响区,焊接过程对不锈钢的腐蚀起到促进作用。随着硫酸介质温度的逐渐升高,基材的钝化膜比较稳定,而焊缝与热影响区的钝化膜会发生破裂;并且各区域的自腐蚀电流与腐蚀速率会逐渐增大,耐腐蚀性逐渐下降。

Corrosion behaviors of the various regions of 304 stainless steel welded joints at different temperatures in concentrated sulfuric acid with mass fraction of 98% were studied by electrochemical impedance spectroscopy and potentiodynamic polarization curve. Results showed that the mainly corrosion form of 304 stainless steel welded joint in concentrated sulfuric acid was pitting corrosion. In the same condition of concen- trated sulfuric acid,the order of corrosion resistance of each region of the welded joints was the base metal,the weld zone and the heat-affected zone, and the welding process could promote the corrosion of stainless steel. With the increase of the temperature of the sulfuric acid, the passi- vation film of the base metal was relatively stable, while the weld zone and heat-affected zone of the passivation film were ruptured. Moreover, the corrosion current and corrosion rate of each area would gradually increase, and the corrosion resistance decreased gradually.