The chromate conversion treatment is widely used, but it requires highly toxic chromic acid solutions with the consequent effluent disposal and ecological problems. The removal of these toxic chemicals is considered a priority within European Union. The corrosion resistance of three alternative treatments applied on electrogalvanised steel, and immersed in aerated 0.3 M Na2 SO4 solution, pH 10, at 25 °C, was investigated using electrochemical techniques. Their performance was compared with the obtained using the traditional Cr6+-based treatment in the same conditions. The achieved results show that the alternative coatings exhibited discrete protective properties in the sulphate solution. The nitro-cobalt chemical conversion treatment showed similar protective properties than the traditional Cr6+-based treatment, while with the Cr3+-based treatment those were very poor. The phosphate treatment initially performed acceptably but as the time elapsed, its protective properties decreased.
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机译：铬酸盐转化处理已被广泛使用，但它需要剧毒的铬酸溶液，从而导致废水处理和生态问题。这些有毒化学物质的去除被认为是欧盟内部的优先事项。使用电化学技术研究了在电镀锌钢上浸泡在25°C的0.3 M Na2 SO4曝气溶液（pH 10）中的三种替代处理的耐腐蚀性。将它们的性能与在相同条件下使用传统Cr6 +基处理获得的性能进行比较。获得的结果表明，替代涂层在硫酸盐溶液中表现出离散的保护性能。硝基钴化学转化处理显示出与传统的基于Cr6 +的处理相似的保护性能，而使用基于Cr3 +的处理则非常差。磷酸盐处理最初可以令人满意地进行，但是随着时间的流逝，其防护性能下降。
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