Corrosion Behavior of Q235B Steel at Early Stage Exposed in Marine Splash Zone in Qingdao

Corrosion behavior of Q235B carbon steel in early stage (0-60 d) was studied by exposure test in Qingdao marine splash zone, corrosion rate calculation, pitting depth test, macroscopic and microscopic morphology observation, rust layer composition analysis and other methods. The results show that with the increase of exposure time, the average pitting depth and maximum pitting depth of Q235B carbon steel increased, and the corrosion rate increased first and then decreased. At 60 d, under the multiple effects of splash impact, high-frequency dry-wet alternation and salt concentration, multiple small pores and local bulges appeared on the surface of Q235B carbon steel, and there were obvious cracks between the corrosion products. The corrosion products were mainly iron oxides. With the extension of exposure time, the content of Fe decreased and the content of oxygen increased. The increase of chloride ions promoted local corrosion. At 60 d, the main phases of corrosion products on the surface of Q235B carbon steel were active substances such as γ-FeOOH, β-FeOOH and Fe₃O₄.