采用不同pH值(9.0～12.0)的饱和Ca(OH)2溶液模拟混凝土因碳化而导致pH值降低的混凝土孔隙液,研究在这些溶液中热镀锌钢筋表面锌酸钙覆盖层的变化和锌层的腐蚀行为,并对实验条件下锌酸钙的溶解转化机理进行了讨论.对浸泡30天后各试样的扫描电镜、能谱分析、X射线衍射、塔菲尔极化和电化学阻抗谱分析结果表明:随孔隙液pH降低和浸泡时间增加,锌层上锌酸钙减少而ZnO增加,当pH值为9时,覆盖层可全部转化为ZnO;随着锌酸钙减少和ZnO增加,极化电阻(Rp)、膜层电阻(Rc)、电荷转移电阻(Rct)和扩散阻抗(Ws)均降低,而自腐蚀电流密度icorr增大,但icorr仍接近钢筋钝化临界值10-1μA/cm2.
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