<正> 一、问题的提出通常以点蚀电位值的高低来相对评价材质抗点蚀的性能。然而对于一个确定的实际钝态体系,点蚀电位不足以判断该体系是否会产生点蚀。因为测取点蚀电位时,试样都处于阳极极化状态下。然而,在阳极极化电位下会产生点蚀,并不意味着自腐蚀状态下必定发生点蚀。对于实际应用来说,判定自腐蚀条件下是否会发生点蚀往往比相对评价材质的抗点性能更为重要。如果测得实际体系的临界点蚀电位((?)_(cb)),并测定或计算出其极限自腐蚀电位((?)_(LC)),那么将两者加以比较就能够判断该体系是否会发生点蚀,即(?)≤(?)_(cb)时发生点蚀,而(?)_(LC)>(?)_(cb)时有可能发生点蚀。
In this paper,a method was proposed to determine the critical pitting potential(φcb)which is obtained by extrapolating the curve of 1/φvsφ to 1/τ=0.A formula,φL=φ_(ε,o)+η_(co),was then derived to calculate the limit free corrosion potentials(φ)of practical passive systems. Finally,the boundary condition for prevention of practical passive sys- tems from pitting initiation was established.That is,if φ_(cb)>φfor a practical passive system,it is impossible for pitting nuclei to oc cur in the system,on the contrary,it is possible if φ_(cb)<φ■.
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