Study on Application of Electrolytic Protection in atmospheritic Environment

将石英晶体微量天平(QCM)和涂有不同量海盐Ws的不锈钢放入恒湿箱中，测量吸水量W&lt；ab&gt；(H2O)。结果表明，当Ws大于10^&lt；-2&gt；g/m^2时，(W&lt；ab&gt；(H2O)/Ws)与Rh成正比，而与Ws无关。这意味着1)水膜厚度与Ws成正比；2)水膜的化学成分和电导率是Rh的函数。测定了不同海盐含量溶液的比重和电导率。这些值被认为等于具有相同(W&lt；ab&gt；(H2O)/Ws)比的水膜的值，以及在不同Ws和RH条件下阳极与缺陷之间的电阻值。发现保护缺陷所需的电压并不是很高，在Ws=10^&lt；-3&gt；g/m^2，RH=40%的条件下，估计保护电压为4.8V，在此条件下腐蚀性较弱。用开尔文探头和QCM分别测量了不同Ws、RH和保护电流密度条件下的电极电位和腐蚀速率。在测量结果的基础上，绘制了内极化曲线。在RH=70%的条件下，其保护电位为-750 mV，保护电流密度为20μA/cm2，腐蚀速率小于0.1μ，m/y。这些电位和电流密度值不受相对湿度的影响。

QCM(Quartz Cristal Microbalance) and stainless steels covered with various ammount of sea salt, Ws, were put in the constant humidity chamber, and amount of absorbed water, W_<ab>(H2O), was measured. It was found that the ratio of (W_<ab>(H_2O)/Ws) was determined as a function of RH and was not depended on Ws, when Ws was more than 10^<-2> g/m^2 . This means that 1) the thickness of water film is proportional to Ws and 2) chemical conposition of waterfilm and conductivity are determined as functions of RH. The specific gravities and conductivities of the solutions with various content of sea salt were also measured. These values were considered to be equal to those of water films which had the same (W_<ab>(H_2O)/Ws) ratio, and resistance values between the anode and the defect under various Ws and RH conditions. It was found that the voltage needed to protect the defect was not so high ; the voltage was estimated to be 4.8V under the conditon with Ws=10^<-3>g/m^2 and RH=40%, under which the corrosivity was considered to be relatively mild.A system to measure potential of Fe electrode and corrosion rate of it was developed. The potential and the corrosion rate were measured by Kelvin probe and QCM, respevtively, under various Ws, RH and potection current density conditions. Base on the measured resalts, the inner polarization curves were drawn. The protection potential and protection current density was determined to be - 750mV vs SCE and 20 μ A/cm^2 , respectively, where corrosion rate was less tan 0.1 μ, m/y, under the condition with RH=70%. These potential and current density values were not affected by RH.