Study on Cathodic Protection with Illumination by TiO2 Coating

不锈钢阴极保护的最佳热处理温度为250ﾟC，此时涂层为-500ﾟ的不锈钢的光电势最低。当热处理温度高于300 mV时，由于不锈钢中的铁、铬和镍在涂层过程中扩散到涂层中，光电势变得更高。最佳热处理温度为250ﾟC的光照样品，即使在黑暗条件下，仍保持相对较低的贵金属电位，-200--300 mV.SCE-这种效应被称为“光记忆效应”，这是用溶胶-凝胶法镀覆的不锈钢的特殊行为。铜阴极保护的最佳热处理温度范围是600-700ﾟC，其中涂有二氧化钛的铜样显示出最低的贵金属光势。在600ﾟC以下处理的样品，铜氧化物似乎是在涂层过程中形成的，并且具有明显的p型光效应。阴极处理在-600 mV c…下进行。此外，还可以消除氧化铜的光致效应，甚至可以在临界温度以下使二氧化钛涂层在铜衬底上表现出光致效应。在适当的热处理条件下，在光照下，在pH为4~12的范围内，在0.3%的氯化钠溶液中，TiO2光催化涂层能有效地保护铜免受腐蚀，这是因为TiO2光催化涂层使除氧溶液和曝气溶液中的光电势都进入了铜的E-pH图中的免疫区域。结果表明，直接涂覆TiO2钢的高光电势是由于涂层过程中Fe向涂层内的扩散所致。在Ti02/钢界面处形成一层氧化铁层，可以抑制这种扩散，大大提高Ti02/钢的光响应能力。在高温(&GT；500ﾟC)处理下，即使在氧化铁层的存在下，也可以观察到Fe的扩散，这是导致TiO2光电势较高的原因。在各种形式的铁氧化物中，α-Fe203被认为是获得不那么高贵的光电势的重要因素，而α-Fe203的性质随氧化温度的变化影响了Ti02/钢的光效。较少

The optimum heat treatment temperature for cathodic protection of stainless steel is 250ﾟC,at which the specimen with TiO2 coating exhibits the least noble photopotential, <-500mV.SCE.Photopotential becomes nobler when heat treatment temperature is higher than 300ﾟC,because Fe, Cr and Ni in the stailess steel diffuse into the coating in the coating process. The potential of the illuminated specimen with the optimum heat treatment temperature, 250ﾟC,remains relatively less noble potential, -200--300mV.SCE,even under the dark condition-this effect is called as "photo memory effect" and specific behavior for the stainless steel coated by the sol-gel method.The optimum heat treatment temperature range for cathodic protection of Cu is from 600 to 700ﾟC,in which Cu specimen with TiO2 coating exhibits the least noble photopotential. Copper oxide seemed to be formed in the coating process and had an obvious p-type photo-effect for the specimens treated below 600ﾟC.Cathodic treatment at-600mV c … More an eliminate the photo-effect of copper oxide, which even can make the TiO2 coating exhibit photo-effect on the Cu substrate below the critical temperature. Given the proper heat treatment condition, the TiO2 coating effectively protects Cu from corrosion in 0.3% NaCl solution over the pH range from 4 to 12 under illumination, because the photopotentials in both deaerated and aerated solutions are driven into the immunity domain in the E-pH diagram of Cu by the TiO2 coating.The photo-electrochemical behavior of TiO2/steel system was investigated. It was found that the noble photopotential for the steel directly coated with TiO2 resulted from the diffusion of Fe into the coating in the coating process. An Fe oxide layr at the TiO2-steel interface can retard this diffusion and greatly improve the photo-response of TiO2/steel. Under high temperature (>500ﾟC) treatment for TiO2 coating, Fe diffusion was observed even in the presence of Fe oxide layr and was responsible for the noble photopotential. Amongst various forms of Fe oxides, alpha-Fe203 was considered to be important for obtaining the less noble photopotential while the property change of alpha-Fe203 with oxidation temperature was shown to influence the photo-effect of TiO2/steel. Less