鋅/二硫化鉬複合電鍍層之抗腐蝕性質研究

Abstract

皂化磷酸鹽鈍化皮膜雖然可兼具抗蝕性及潤滑性，但皮膜上殘留的孔隙易降低抗蝕性、高碳排製程、任意排放導致水質優養化等缺點，而複合電鍍為目前可用來取代皂化磷酸鹽鈍化處理的方法之一，以優化整體製程品質與降低對環境衝擊。 本研究藉由在純鋅電鍍液中添加MoS2顆粒，並以脈衝電鍍製作Zn-MoS2複合鍍層於S45C中碳鋼板上，希望結合鋅的犧牲保護機制與MoS2的層狀結構能提供潤滑性，使複合鍍層有更完善的性能。經實驗所製備的純鋅鍍層與Zn-MoS2複合鍍層，透過光學(OM)和電子顯微鏡(SEM)觀察試樣之表面、橫截面形貌，並藉由電子顯微鏡所搭配的背向散射電子影像(BSE)和能量散佈X射線譜儀(EDS)，分析MoS2顆粒在鋅鍍層中的組成分布、X光繞射分析儀(XRD)了解鋅沉積的結晶行為，並使用動電位極化和電化學交流阻抗圖譜(EIS)，解析鍍層在長時間浸泡(1、6、12、24小時)於3.5 wt.%氯化鈉水溶液的腐蝕行為，了解添加MoS2顆粒於純鋅鍍層後，對整體形貌與抗蝕性的影響。 實驗結果顯示，Zn-MoS2複合鍍層以樹枝狀的方式生長，提高表面粗糙度，同時當MoS2顆粒鑲嵌於鍍鋅層中有觀察到顆粒的團聚現象，造成鍍層均勻性會下降且因局部應力變大而有缺陷產生。XRD分析結果顯示MoS2顆粒的添加會影響鋅鍍層的結晶行為，呈現無優選結晶方位。對比兩者在長時間浸泡後之微結構，可發現皆有相似的腐蝕產物形貌，但在腐蝕速度的進程上，複合鍍層較純鋅鍍層快，且在浸泡24小時之複合鍍層橫截面有觀察到底材外露的情況。經電化學結果發現，兩種鍍層皆有隨時間增加而抗蝕性增加，但複合鍍層於浸泡24小時即發生底材外露，失去保護力，以上結果皆顯示MoS2顆粒的添加不利於增加抗腐蝕性。 最後挑選二篇使用相似複合鍍層系統的文獻進行比較，並探討本實驗和文獻結果之間的差異，從對比鍍液系統、電鍍參數、MoS2顆粒的選用，兩篇皆發現顆粒添加有助增加抗蝕性，推測主因是MoS2顆粒的選用，另一個為鍍層所製備的厚度能減少缺陷。

Saponified phosphate conversion coatings offer both corrosion resistance and lubrication. However, they present several disadvantages, including residual porosity that compromises corrosion resistance, high carbon emissions during processing, and eutrophication risks from wastewater discharge. Composite electroplating has emerged as a viable alternative, aiming to enhance process quality while reducing environmental impact. This study investigates Zn-MoS₂ composite coatings produced using pulse electroplating from a zinc bath with dispersed MoS₂ particles, applied to S45C medium-carbon steel. By combining zinc’s sacrificial protection with MoS₂’s layered lubricating structure, the goal is to improve overall coating performance. Coating morphology was analyzed using Optical Microscope(OM) and Scanning Electron Microscope(SEM), along with Backscattered electron (BSE) imaging and Energy Dispersive X-ray Spectroscopy(EDS) to assess particle distribution. Crystallographic properties were evaluated by X-ray Diffractometer (XRD), and corrosion behavior was analyzed via Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) after immersion in 3.5 wt.% NaCl solution for 1, 6, 12, and 24 hours. Results showed dendritic growth in the Zn-MoS₂ coatings, increasing surface roughness. Agglomeration of MoS₂ particles was observed, which reduced coating uniformity and introduced defects due to localized stress. XRD analysis results show that the addition of MoS₂ particles affects the crystallization behavior of the zinc coating, exhibiting no preferred crystallographic orientation. While both coatings displayed similar corrosion products, but the composite layer corroded more quickly, with cross-section evidence indicated substrate exposure after 24 hours of immersion. Electrochemical tests showed improved resistance over time for both, but the composite coating ultimately lost its protective function. These results indicate that MoS₂ incorporation did not enhance corrosion resistance. Finally, two similar studies were compared. Differences in plating bath composition, deposition parameters, and MoS2 particle types were compared. Both studies reported performance improvements with particle addition, likely due to better particle selection and increasing coating thickness could help minimize defects.