涂层金属的耐腐蚀性能取决于其对腐蚀介质的的阻挡能力，在水溶液及含水大气中则主要取 决于水分子及其它侵蚀性粒子(O2、Cl-等)的渗透能力.介绍了Fick扩散条件下H2O在 涂层中的扩散行为及其与涂层阻抗间的关系，并探讨阻抗方法在涂层评价中的适用条件.
In the present paper a review was given on water di ffusion behaviors in polymer films and coating impedance according to Fickian pr ocess.In the case of linear Fickian diffusion,a mathematical relationship betwee n the water-uptake in organic coatings and capacitance,C,of coatings was est ablished.The change rate of coating capacitance was mainly depended on the water diffusion coefficient,D,in coatings.In the initial stage of water-uptaking, a linear relationship is shown in the curves lnC(t)～time0.5,with the slope proportional to D0.5.Under the non-linear diffusion,water prefe rentiall y penetrated through the cracks or the boundaries of foreign particles by sheari ng diffusion,while in the bulk coatings by linear one.The contribution by linear diffusion could be eliminated with the presence of obvious porosity,and the coa ting capacitance was mainly determined by the porosity of coatings,θ.The sl ope of the linear part in lnC(t)～t0.5 curves was proportional to θ 0.5.
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