Replacing the chromate and phosphate conversion coatings (CCs) with nontoxic ones has played a key role in CC research in recent years. Although considerable efforts have been devoted to discovering and modifying the toxic CC alternatives, much of the research has been restricted to a few numbers of green CCs. The present study has aimed to review the recent attempts that have been made in this area of research to address the toxicity issue of CCs, with a focus on the steel substrate. It includes investigations on different CCs: cerium (CeCC), neodymium (NdCC), lanthanum (LaCC), zirconium (ZrCC), titanium (TiCC), trivalent chromium (TCC), molybdate (MoCC), silicate (SiCC), and silane (SilCC). Surface studies, electrochemical measurements, CCs’ comparison, and film formation mechanisms were summarized. Imparting adhesion to the steel/organic coating interface or the delamination of the organic coating was discussed. Moreover, the influence of several steel substrates (coated and uncoated) and solution parameters (pH, temperature, concentration, stirring, and immersion time) on the CCs properties were outlined. Various methods (such as additives, heat treatment, and subsequent film treatment) that have been employed to improve the green CCs properties and make them comparable to their harmful counterparts were explored.

近年来，用无毒涂层代替铬酸盐和磷酸盐转化涂层 (CC) 在 CC 研究中发挥了关键作用。尽管在发现和修改有毒 CC 替代品方面付出了相当大的努力，但大部分研究仅限于少数绿色 CC。本研究旨在回顾最近在该研究领域为解决 CC 的毒性问题所做的尝试，重点是钢基材。它包括对不同 CC 的研究：铈 (CeCC)、钕 (NdCC)、镧 (LaCC)、锆 (ZrCC)、钛 (TiCC)、三价铬 (TCC)、钼酸盐 (MoCC)、硅酸盐 (SiCC) 和硅烷(SilCC)。总结了表面研究、电化学测量、CC 的比较和成膜机制。讨论了赋予钢/有机涂层界面的附着力或有机涂层的分层。此外，还概述了几种钢基材（涂层和未涂层​​）和溶液参数（pH、温度、浓度、搅拌和浸泡时间）对 CCs 性能的影响。探索了用于改善绿色 CCs 特性并使它们与有害的同类物相媲美的各种方法（例如添加剂、热处理和随后的薄膜处理）。