Uv Light Influence On The Corrosion Behavior Of The Effect Of Rust Layer Of Photoelectric Catalysis

The metal corrosion is inevitable in many industrial fields, and the extent of corrosion will lead to different damages and accident as well. The rust layers were the corrosion products accumulated on metal surface, mainly were some unstable mixture just as Fe2O3, FeOOH Fe2O3·XH2O and so on. The corrosion behavior under the rust layers is long-term and complex process, and the layers have corrosion-resistant effect when it accumulate to enough thickness, but that semiconductor oxide film may occur photoelectric catalytic reaction in suitable light conditions, so it have a greater impact on the electrochemical corrosion behavior of low carbon steel..In this paper, the method of electrochemical impedance spectroscopy (EIS) was used to study the photoelectric catalytic reaction of the rust layers. The results show that the rust layer under UV can lead to photoelectric catalytic reaction, and what can accelerate the substrate electrode corrosion rate. After that, change the light conditions we found both of UV and visible light can cause the photoelectric catalytic reaction of the rust layers, but it is more effective under UV than visible sight. What’s more, through contrast test the impedance values under UV and under visible light we believe visible light can only be partially absorbed generate a certain photoelectric catalytic reaction. Use XRD experiment to the rust which exposed to air110day we found iron oxide a-FeOOH, β-FeOOH, γ-FeOOH and Fe3O4are included, combination with semiconducting properties of these substances that γ-FeOOH, Fe2O3, Fe3O4or one of them maybe the component cause the photoelectric catalytic reaction.In the experiment of qualitative analysis of the product solution, we think the O2which participation reduction reaction at the cathode can generate traces of H2O2in the solution. Comparative the EIS rweults of rust layers electrode by add a trace H2O2in solution that the existence of H2O2can affect the electrical chemical corrosion behavior as well.At last, we simulated the long-term corrosion process in three different situations, exposure to the air, immerse in3.5%NaCl solution and dry-wet cycle alternate in3.5%NaCl. We found corrosion behavior or rust layers on low carbon steel is generally divided into two stages, the corrosion rate increased than the bare electrode in the initial stage, and the corrosion product can accelerate the electrochemical corrosion behavior, while it decreased in the later stage. And by XRD experiment we believe the formation of Fe3O4and α-FeOOH maybe one of the factors that the corrosion rate appears conversion. The ability of the rust layers’photoelectric catalytic effect under UV accelerate substrate electrode corrosion is gradually increased in initial stage, while with the rust layers accumulated to a certain thickness, the effect of the photoelectric catalytic to maintain a certain intensity.