Effect of different surface treatments on corrosion behavior of 300m steel in qingdao marine atmosphere

Atmospheric exposure of three types of 300M steel with different surface treatments (bare material, Cd-Ti Plating of low hydrogen embrittlement, high-velocity oxygen-fuel (HVOF) sprayed WC-10Co4Cr coating) were conducted for 2 a in Qingdao marine atmosphere. Then the corroded steels were characterized via surface and cross-section morphology observation and corrosion products analysis. The results of the two-year atmospheric exposure test are as follow: the HVOF sprayed WC-10Co4Cr coating peeled off, while galvanic corrosion and crevice corrosion occurred between the coating and the substrate which acted as anode, and the corrosion rate was the fastest and the corresponding corrosion pits were the deepest. While the corrosion potential of the Cd-Ti plated steel was lower than that of the substrate, and the plating was corroded prior to the substrate. The corrosion rate of the plated steel was the slowest and the corresponding corrosion pits were shallow, which indicated that the protective effect of Cd-Ti plating was the best among the three. The corrosion products on the bare steel as well as the substrate beneath the HVOF coating were mainly composed of α-FeOOH, β-FeOOH, γ-FeOOH and Fe₃ O₄, but Cd(OH)₂ and CdO₂ were also appeared on the surface of the steel with Cd-Ti plating. The protective effect of Cd-Ti plating was obvious because of sacrificial anode protection, but the HOVF sprayed WC-10Cr4Cr caused galvanic corrosion and crevice corrosion, which aggravated the corrosion of the substrate.