本研究利用低碳鋼為底材，以複合式熱浸鍍 Zn 和熱浸鍍 Zn– 5wt. % Al–2 wt. % Mg，於 425 ℃ ~ 475 ℃ 進行 60 秒到 600 秒的熱浸鍍，研究不同溫度時間參數對鍍層生長過程的影響及不同鍍層形貌的耐蝕性。結果顯示，複合式熱浸鍍可形成五層結構，最外層的鍍層與鋅鋁鎂鍍浴的成分相同，而由外而內又可分為Zn + MgZn2 + Al86Fe14層、Fe2Al5層、Zn + (Zn+MgZn2) + (Zn+MgZn2+Al)inner 層、Fe2Al5Zn + Zn層。隨第一鍍(鍍鋅)時間拉長，因鐵鋅介金屬支架成長，第二鍍(鍍鋅鋁鎂)後整體鍍層厚度也隨之增加。當浸鍍鋅鋁鎂時間增長，在 240 秒後僅有 Fe2Al5Zn + Zn層會成長。第一鍍的鍍鋅時間主要影響整體鍍層厚度，第二鍍的溫度及時間影響外層披覆的鋅鋁鎂厚度及Fe2Al5Zn + Zn層厚度。經研究結果顯示，鍍層厚度主要影響耐蝕性，含鎂鍍層 Zn + (Zn+MgZn2) + (Zn+MgZn2+Al)outer 層、Zn + MgZn2 + Al86Fe14層、Zn + (Zn+MgZn2) + (Zn+MgZn2+Al)inner 層之厚度總合和愈厚，耐蝕性愈為提升。

In this study, for research how second hot-dip influence coatings. Low carbon steel was used as the substrate, Zn and Zn – 5 wt. % Al – 2 wt. % Mg was second hot-dipped at 425 ℃ ~ 475 ℃ for 60 seconds to 600 seconds. The experiment shows that coating could be result in five layers. The outer layer had the same composition with the Zn - Al - Mg alloy bath and other four layers had been named as Zn + MgZn2 + Al86Fe14 layer, Fe2Al5 layer, Zn + (Zn+MgZn2) + (Zn+MgZn2+Al)inner layer, Fe2Al5 + Zn layer from outside to inside. Since the longer time did the first-dip goes, the whole layer went thick after the second-dip, but the Fe2Al5 + Zn layer inside reduce. When you got longer time for second-dip Zn-Al-Mg, the layer only goes thick before 240 seconds. It could be observed that the Fe composition decrease in Zn + (Zn+MgZn2) + (Zn+MgZn2+Al)inner at 425 ℃ ~ 475 ℃. Due to the study, the first-dip mainly affect the thinkness of whole layer and different temperature and time in second-dip had influence on the growth of Fe2Al5 + Zn layer. According to EIS experiments, the corrosion resistance went better when layers contained in Mg went thicker.

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