Study On The Photo Corrosion Behavior And Preparation Of Photo-generated Anticorrosion Coatings

The study of the different corrosion behavior of weathering steel and stainless steel can further understand the mechanism and base on the mechanism coatings are prepared for corrosion protection of offshore steel structures.This article is divided into two parts:the first part explores the response mechanism of corrosion products formed on the surface of Q450 weathering steel and 316L stainless steel under visible light illumination;in the second part prepare the cuprous oxide film coupled with stainless steel based on the mechanism in the first part,and analyze the photogenerated cathodic protection effect for stainless steel.In the first part Q450 weathering steel and 316L stainless steel were selected as the research objects,in the simulated marine atmosphere corrosion under certain corrosion cycle,by SEM,Raman,FT-IR,XPS corrosion products of weathering steel were found that mainly composed of Fe₂O₃/FeOOH,Fe₃O₄ appeared inner 3nm;stainless steel surface was mainly composed of FeOOH,Fe₂O₃ and a small amount of Cr₂O₃?Cr?OH?₃.At the same time,it was found through electrochemical tests that the weathering steel exhibited a positive photovoltage and the stainless steel exhibited a negative photovoltage.The corrosion progress of weathering steel was promoted under illumination condition and increased corrosion cycle.However,the corrosion product film formed after 7 days of corrosion under illumination had the function of protecting the matrix and delaying the corrosion.Illumination delayed the corrosion process of stainless steel and improved the integrity of the film.Finally,the mechanism and model of the influence of visible light on the corrosion products of two kinds of steel and the corrosion process of the matrix were established.The second part cuprous oxide film was prepared by electrochemical deposition method,by XRD,XPS,SEM,and UV-vis it was found that under the condition of different pH value of the solution and different deposition potential,cuprous oxide films were composed of cuprous oxide and metal impurity Cu.The change of pH value and deposition potential will result in the difference of crystalline properties of cuprous oxide crystals and Cu impurities.The higher pH value and more negative deposition potential will lead the worse crystallinity of cuprous oxide and impurity Cu crystals.The increase of pH value and more negative deposition potential will result in the decrease of the grain size of cuprous oxide,and the more negative deposition potential,the more impurity Cu on the surface of the film.The increase of the pH value will change the semiconductor structure of cuprous oxide thin film;with the increasing pH,the band gap of semiconductor Cu₂O decreased;and the deposition potential will not affect the semiconductor structure of cuprous oxide thin film.At the same time,the photo-electrochemical tests show that the Cu₂O thin film exhibited the characteristic of N-type semiconductor,as well as the negative photovoltage and positive photocurrent under visible light.The pH value and deposition potential can affect the photoelectric properties of the film and the cathodic protection on the stainless steel.