硫化物對三價鉻電鍍行為的影響

Abstract

三價鉻電鍍製程是具有前瞻性的替代六價鉻方案之一。本研究為解析硫化物對三價鉻電鍍行為的影響，藉由添加幾種型式的硫化物於三價鉻電鍍液中進行電鍍，以釐清硫化物於電鍍行為中所扮演的角色。利用光學顯微鏡、掃描式電子顯微鏡觀察鍍層表面之形貌，再利用X光繞射分析儀、穿透式電子顯微鏡和X射線光電子能譜儀解析鍍層的結晶性和元素分佈；為了進一步探討電鍍行為的影響以及鍍層的抗蝕性質，使用電化學極化分析以及交流阻抗法進行研究，最後根據實驗結果的比較跟統整，解析硫化物對三價鉻電鍍行為，以及鍍層微結構、結晶性和抗蝕性的影響。 實驗結果顯示，硫化物的添加會導致鍍層表面形貌的改變，並且併入些許的硫，而抑制了錯合劑中碳的大量共鍍，進而改善了鍍層的結晶性。由於從原先較具脆性的非晶質轉變成結晶性鍍層，使得鍍層的內應力下降，裂紋數明顯減少，進一步改善了鍍層的抗蝕性。因此，藉由控制鍍液中的硫化物濃度，可以調整三價鉻鍍層組成元素、結晶形貌、內應力以及抗腐蝕的能力。

The electrodeposition process of trivalent chromium is one of the promising replacements of hexavalent chromium electrodeposition. In this study, some organic or inorganic sulfides have been added to the trivalent chromium solution to study how the sulfides in the solution affect the microstructure and properties of the deposits, as characterized by SEM, XRD, TEM, EDS, XPS, respectively. Furthermore, owing to analyzing the sulfide influences to corrosion resistance and reduction mechanism of trivalent chromium system, polarization curve and EIS measurement were further applied. The experimental results reveal that the sulfide addition changes the morphology and co-deposits S in the deposits. Furthermore, the C co-deposition from the complexant is inhibited; therefore, the crystallinity of deposits changes apparently. Owing to the transformation from amorphous to crystalline, the internal stress and cracks of the deposits decrease. Therefore, the corrosion resistance is highly improved. By controlling the concentration of sulfide in the solution, the composition, crystallinity, internal stress, and corrosion resistance of the deposits can be modified.