The use of alkaline electroplating baths is the essential requirement to deposit Cu directly onto steels because of non-adherent Cu formation by replacement reaction between Cu²⁺ and Fe in acidic solution. For the development of such an electroplating bath, complexing agents to form soluble Cu complex in alkaline pH is necessary at first. Secondary, the soluble Cu complex must be reduced electrochemically. Cyanide-based baths meet these requirements, but the bath is toxic. In this study, the survey of complexing agents revealed that citric and tartaric acids form soluble copper complex solutions in alkaline pH, and electroplating is possible. The cathodic current density range to obtain smooth and adhesive electroplating with citrate complexed bath was extensive than that with a tartrate bath. It was found that 0.1 mol dm⁻³ CuSO₄ - 0.5 mol dm⁻³ citric acid baths with pH of 9–11 are optimum to obtain adhesive and uniform Cu layer. Copper electroplating with an acidic CuSO₄–H₂SO₄ bath was possible on 1 µm Cu layer with the alkaline citrate bath. Because the plating rate is high with the acidic bath, the multilayer Cu electroplating from the citrate bath and then an acidic sulfate bath gives a reasonable way for Cu coating onto steels. Elongation test of the steel sheet electroplated with the multilayer Cu showed that detachment of the Cu layer was limited in the vicinity of the broken part of the sheet. It is concluded that the toxic cyanide Cu plating bath can be replaced with a citrate bath.

使用碱性电镀液是直接将Cu沉积到钢上的基本要求，因为通过Cu ²⁺之间的置换反应会形成不粘附的Cu和铁在酸性溶液中。为了开发这样的电镀浴，首先需要在碱性pH下形成可溶性Cu络合物的络合剂。第二，可溶性铜络合物必须通过电化学还原。基于氰化物的镀液满足这些要求，但镀液有毒。在这项研究中，对络合剂的调查表明，柠檬酸和酒石酸在碱性pH值下会形成可溶性铜络合物溶液，并且有可能进行电镀。与使用酒石酸盐浴相比，使用柠檬酸盐络合浴获得平滑且粘附性电镀的阴极电流密度范围更大。结果发现，0.1摩尔分米^-3的CuSO ₄ - 0.5摩尔分米^-3pH为9-11的柠檬酸浴最适合获得粘合力和均匀的Cu层。铜与酸性硫酸铜电镀₄ -H ₂ SO ₄浴可能在1 μ米，碱性柠檬酸浴的Cu层。由于用酸性镀液进行镀覆的速率很高，因此从柠檬酸盐镀液然后再进行酸性硫酸盐镀液的多层镀铜，为在钢上镀铜提供了一种合理的方法。镀有多层Cu的钢板的伸长试验表明，在薄板的断裂部分附近，Cu层的剥离受到限制。结论是，可以用柠檬酸盐浴代替有毒的氰化铜镀浴。