Hot-dip galvanizing is one of the most common corrosion protection techniques for steel. This widely available method increases the lifetime of steel structures by up to 50 years. Although there is a well-established method for hot-dip galvanizing of structural mild-steel, the effects of this method on mechanical properties of high and ultra-high strength steels (HSS and UHSS), with nominal yield strength greater than 700MPa, has not been thoroughly studied. The study of galvanized thin-walled HSS and UHSS tubes is important since (a) galvanizing heat can easily penetrate the small thickness of thin-walled tubes and change their mechanical behaviour, (b) these materials are made through special heat treatment process which might render them sensitive to heat exposure during hot-dip galvanizing, and (c) these materials are high in alloy especially Si equivalent (Si+P) content which categorizes them as reactive steel with rapid reaction with molten zinc. Therefore, to deeply study the performance of galvanized high-grade steels, HSS and UHSS thin-walled tubes were dipped in zinc bath for various durations. For each bath time, a tube with intact and one with sand-blasted surface were used so that the roughness effect of the steel surface on coating performance could be explored. Dog-bone, tube shape, and small beam-shaped specimens were cut out of the larger tubes for tensile, compressive, impact, microscopy, coating thickness, and hardness studies. A mild steel tube was also galvanized and studied as a control specimen for comparison purposes. These studies showed that after galvanizing, HSS and UHSS materials lost their ultimate stress and recovered some of their ductility. On the other hand, galvanized mild steel specimens lost a small portion of their ductility and gained higher yield and ultimate stresses. In addition, it was found that galvanizing did not affect the hardness of HSS materials but decreased the hardness of UHSS materials up to 10%. Coating studies were conducted through thickness measurements, impact tests, and microscopic studies. The measurements showed that the coating thickness increased with respect to bath time and that a thicker coating formed on sand-blasted surfaces. Moreover, impact tests and microscopic studies on plastically bent HSS and UHSS specimens demonstrated that the favourable coating in terms of cracking under severe plastic deformation was formed on non-sand-blasted steel surfaces which were experienced a zinc bath time of 1.5 min. The outcomes of this study have the potential to be incorporated into the codes of practice and design guidelines for suitable hot-dip galvanizing and design of structural components made of galvanized HSS and UHSS.

热浸镀锌是最常见的钢腐蚀防护技术之一。这种广泛使用的方法可将钢结构的寿命延长多达50年。尽管有一种成熟的结构低碳钢热浸镀锌方法，但该方法对标称屈服强度大于700MPa的高强度和超高强度钢（HSS和UHSS）的机械性能的影响没有被彻底研究。镀锌薄壁HSS和UHSS管的研究非常重要，因为（a）镀锌热很容易穿透小厚度的薄壁管并改变其机械性能，（b）这些材料是通过特殊的热处理工艺制成的，这种工艺可能使它们对热浸镀锌过程中的热暴露敏感，（c）这些材料的合金含量高，尤其是硅当量（Si + P）含量高，可将其归类为反应性钢，并与熔融锌快速反应。因此，为了深入研究镀锌高级钢的性能，将HSS和UHSS薄壁管浸入锌浴中不同的时间。对于每个沐浴时间，使用一根完好无损的管子和一根表面喷砂处理的管子，以便研究钢表面的粗糙度对涂层性能的影响。从较大的试管中切出狗骨头，试管形状和小梁形样品，以进行拉伸，压缩，冲击，显微镜检查，涂层厚度和硬度研究。还对低碳钢管进行了镀锌，并作为对照样品进行了研究，以进行比较。这些研究表明，镀锌后，HSS和UHSS材料失去了最终的应力，并恢复了一些延展性。另一方面，镀锌低碳钢试样失去了一小部分的延展性，并获得了更高的屈服强度和极限应力。另外，发现镀锌不影响HSS材料的硬度，但是使UHSS材料的硬度降低多达10％。涂层研究是通过厚度测量，冲击试验和微观研究进行的。测量表明，涂层厚度随浴时间的增加而增加，并且在喷砂表面上形成了较厚的涂层。而且，对塑性弯曲的HSS和UHSS试样进行的冲击试验和微观研究表明，在经历了1.5分钟的锌浴时间的非喷砂钢表面上，在严重塑性变形下开裂方面形成了有利的涂层。这项研究的结果有可能被纳入适用的热浸镀锌和由镀锌的HSS和UHSS制成的结构部件设计的操作规范和设计指南中。