Electrodeposited Zn-Mn alloy coatings are known to provide excellent corrosion resistance to steel due to their ability to form compact corrosion products when exposed to corrosive media. However, obtaining good quality coatings using conventional direct current (DC) electrodeposition from additive free baths is challenging. Pulsed current (PC) deposition has been reported for various Zn based alloy systems to obtain coatings with superior corrosion resistance properties. In this work, Zn-Mn coatings containing up to 9.2 wt. % Mn were electrodeposited on steel from additive-free chloride electrolytes using both DC and PC electrodeposition. Cyclic voltammetry, potentiostatic measurements, Hull cell experiments and SEM-EDS studies indicated good quality DC deposited Zn-Mn coatings in the current density range of 40-60 mA cm⁻² with clustered plate morphology at low and cauliflower morphology at higher current densities. PC deposited coatings showed increased Mn contents and improved corrosion rates. The coating deposited at a low duty cycle and a high frequency showed a fine and compact microstructure with the highest Mn content of 9.2 wt. %. XRD studies showed a complete change in phase composition from a monophasic η-Zn-Mn coating with DC to a monophasic ε-Zn-Mn with PC deposition. Electrochemical impedance analysis revealed porous corrosion products in DC coating, whereas the PC coating formed a compact corrosion product which inhibited the dissolution of Zn and Mn, thus providing higher resistance to corrosion. XRD analysis of the samples after corrosion confirmed the presence of zinc hydroxy chloride (ZHC) as a corrosion product. In summary, PC electrodeposited Zn-Mn coatings provided superior corrosion resistance than those obtained through DC.

众所周知，电沉积 Zn-Mn 合金涂层可以为钢提供出色的耐腐蚀性，因为它们在暴露于腐蚀性介质时能够形成致密的腐蚀产物。然而，使用常规直流 (DC) 电沉积从无添加剂浴中获得优质涂层具有挑战性。据报道，脉冲电流 (PC) 沉积可用于各种锌基合金系统，以获得具有优异耐腐蚀性能的涂层。在这项工作中，Zn-Mn 涂层的含量高达 9.2 重量％。% Mn 使用 DC 和 PC 电沉积从无添加剂的氯化物电解质电沉积在钢上。循环伏安法、恒电位测量、赫尔电池实验和 SEM-EDS 研究表明，在 40-60 mA cm 的电流密度范围内具有优质的直流沉积 Zn-Mn 涂层⁻²具有低电流密度下的簇状板形态和较高电流密度下的花椰菜形态。PC 沉积涂层显示出增加的 Mn 含量和提高的腐蚀速率。以低占空比和高频沉积的涂层显示出精细和致密的微观结构，最高 Mn 含量为 9.2 重量％。%。XRD 研究表明，相组成从 DC 的单相 η-Zn-Mn 涂层到 PC 沉积的单相 ε-Zn-Mn 发生了完全变化。电化学阻抗分析显示DC涂层中存在多孔腐蚀产物，而PC涂层形成致密的腐蚀产物，抑制了Zn和Mn的溶解，从而提供了更高的耐腐蚀性。腐蚀后样品的 XRD 分析证实了羟基氯化锌 (ZHC) 作为腐蚀产物的存在。总之，