丝束电极研究镀锌层存在点缺陷的锌/钢电偶腐蚀行为

Wire beam electrode technique for investigating galvanic corrosion behavior of galvanized steel-spot defect

采用3种不同配置比例的锌/碳钢异材质丝束电极,模拟镀锌层存在不同大小点缺陷时的热浸镀钢,研究锌/钢电偶在不同腐蚀阶段的电位和电流密度分布。结果表明,在钢丝与锌丝面积比为1?120、9?112和25?96的3种情况下,锌丝均能给钢丝提供足够的阴极保护,且锌丝之间存在明显的电位、电流分布不均现象,主要阳极区先随机地在邻近钢丝的锌丝区域内转移,而后逐渐向远端锌丝扩展;钢丝之间也存在电化学参数分布不均一现象,钢丝在受到保护的同时表面会有氢原子析出,且随着阴、阳极面积比的增大,析氢电流密度逐渐减小。

Three kinds of wire beam electrodes（WBE） composed of zinc and mild steel wires were developed,which were used to simulate hot-dip galvanized steel with spot coating defect at different dimensions,to obtain the spatial distributions of potential and current density and their variations with time during the galvanic corrosion.The results show that the zinc wires within WBEs can provide enough cathodic protection to steel wires after immersed in seawater,with surface area ratio of zinc wires to steel wires as 1：120,9：112,and 25：96,respectively.The potential and current density distributions are found to be inhomogeneous among zinc wires;firstly,the main anodic areas shift randomly among the zinc wires adjacent to steel wires,then transfer to the direction away from steel wires,and finally occur on the zinc wires farther.The similar heterogeneous phenomenon also appears on steel wires surface on which hydrogen evolution may take part in the cathodic process occurred.Meanwhile,the current density of water molecule reduction reaction decreases with the ratio of the surface area of steel wires to zinc wires increasing.