Tris-HCl和Tris对镁合金腐蚀的影响

曾荣昌 山东科技大学

近日，《Journal of Materials Science & Technology 》在线发表了我们课题组最新研究工作，题为“New insights into the effect of Tris-HCl and Tris on corrosion of magnesium alloy in presence of bicarbonate, sulfate, hydrogen phosphate and dihydrogen phosphate ions”论文。  

体外降解实验是一种低成本地筛选医用镁合金的途径。镁合金腐蚀产物对其耐蚀性能产生重要影响。目前还没有大家接受的镁合金腐蚀评价准则。Tris作为一种缓冲剂，并非人体成分，有时被加入人体模拟体液。因此，有必要理解Tris缓冲剂对镁合金腐蚀的影响。

我们通过析氢、pH测量和电化学实验对比研究了人体模拟体液中四种阴离子HCO₃⁻、SO₄^2−、HPO₄²⁻ 和 H₂PO₄⁻存在时Tris-HCl 和Tris 分别对镁合金 AZ31 腐蚀行为的影响。

结果表明，Tris-HCl缓冲液阻滞镁合金腐蚀产物膜的形成，镁合金发生均匀腐蚀，腐蚀速率增加。而Tris 则导致镁合金发生点蚀或者均匀腐蚀，降低镁合金腐蚀速率。镁合金在Tris-HCl中的析氢速率和腐蚀电流密度高于单独Tris和无Tris存在时一个数量级。这是因为Tris的氨基水解引起溶液pH 值升高,有助于HCO₃^−、SO₄^2−、 HPO₄²⁻ 和 H₂PO₄⁻形成腐蚀产物膜。最后，提出了镁合金在Tris-HCl 和 Tris存在时的腐蚀机理。

镁合金在0.9%NaCl 溶液中（a）Tris-HCl,（b）Tris的腐蚀机理图

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