臺灣博碩士論文加值系統

本文探討不同酸洗前處理對AZ91D鎂合金錫酸鹽化成皮膜微結構的影響，並釐清酸洗處理後，錫酸鹽皮膜顆粒在AZ91D底材不同相上方成核機制，最後再以鹽霧試驗量測不同前處理後錫酸鹽化成皮膜之抗蝕性質。
實驗結果顯示以11wt% HF進行酸洗前處理後，SEM觀察下可看到底材表面局部區域有溶蝕的現象發生，而以0.5wt% HF進行酸洗前處理後，底材受到的溶蝕程度則較不嚴重，以0.5wt% HNO3進行酸洗處理後，α相受到侵蝕速率大於ß相，底材呈現凹凸不平整之表面狀態。在橫截面TEM 觀察下，以11wt% HF、0.5wt % HF與0.5wt% HNO3酸洗前處理後試樣，表面皆覆蓋了一層鈍化膜，比較鈍化膜微結構後發現，11wt% HF酸洗後所形成的鈍化膜較0.5wt% HNO3酸洗後所形成鈍化膜緻密，0.5wt% HF鈍化膜的緻密程度則介於11wt%HF與0.5wt% HNO3之間。在後續的化成處理中，以11wt% HF或0.5wt%HNO3酸洗前處理後的試樣，在30秒化成處理內皮膜顆粒先於ß相及其相鄰的位置上成核。將化成時間延長至10分鐘後，試樣表面則佈滿錫酸鹽化成皮膜。橫截面SEM觀察發現，經11wt% HF酸洗後化成皮膜顆粒的堆疊較為密集且顆粒與顆粒間縫隙較小，以0.5wt% HF或0.5wt% HNO3酸洗後化成皮膜顆粒的堆疊則會在局部區域，顆粒與顆粒間會出現略為粗大的縫隙。鹽霧試驗果則顯示經11wt%HF酸洗處理後，皮膜顆粒堆疊較為緊密，因此抗蝕性較為良好，當以0.5wt%HF、0.5wt%HNO3酸洗處理後，皮膜顆粒堆疊不夠緊密，進而產生過大的縫隙時，抗蝕性則會下降。

The purpose of this study is to explore the effect of various pickling pretreatments on the nucleation and microstructure of stannate conversion coating on AZ91D magnesium alloy, with emphasis on the effect of theα and β phases of AZ91D.The salt spray test was used to investigate the corrosion resistance of stannate-coated samples with different pickling pretreatments.
Local dissolution was observed on the AZ91D substrate after pickling in 11 wt% HF solution.　This local dissolution was less severe in 0.5 wt% HF solution. Theα phase was more severely attacked than theβ phase in 0.5wt% HNO3 solution, resulting in a relatively rough surface. Cross-sectional TEM showed the presence of a passive layer on the surface of the AZ91D substrate after pickling preatment. Among the various passive layers, the one formed in 11wt% HF solution was the most compact, whereas the counterpart formed in 0.5 wt% HNO3 solution was the most porous. After 30 s of conversion coating treatment,　stannate conversion coating nucleated preferentially on the ß phase or the area near the ß phase for the substrate after pickling in 11 wt% HF solution or 0.5 wt% HNO3 solution. When the conversion treatment was prolonged to 10 min, the sample was nearly completely covered with the conversion coating. The compact density of stannate conversion coating on the 11 wt% HF-pretreated sample was higher than those on the 0.5 wt% HF-pretreated or 0.5 wt% HNO3-pretreated samples. For example, the interstices in between magnesium stannate particles were more frequently observed on the samples with 0.5 wt% HF or 0.5 wt% HNO3 pretreatments. As a result, the stannate-coated sample with 11 wt% HF pickling pretreatment had better corrosion resistance than the counterparts with 0.5 wt% HF or 0.5 wt% HNO3 pretreatments.

摘要i
Abstactii
總目錄iv
圖目錄 viii
表目錄 xii
第一章 前言3
第二章 文獻探討3
2-1鎂合金簡介3
2-1-1鎂與鎂合金3
2-1-2鎂合金分類3
2-2鎂合金的腐蝕行為4
2-2-1鎂的腐蝕行為概述4
2-2-2鎂合金在不同成分溶液下的腐蝕行為4
2-2-3鎂合金在不同微結構的腐蝕行為8
2-3鎂合金的表面處理8
2-3-1表面前處理8
2-3-2陽極氧化處理.11
2-3-3電鍍/無電鍍處理11
2-3-4化成處理12
2-3-5鉻酸鹽化成處理12
2-3-6磷酸鹽/錳酸鹽化成處理13
2-3-7稀土鹽類化成處理14
2-3-8錫酸鹽化成處理15
2-3-9酸洗前處理對化成皮膜生成影響16
第三章 實驗方法及步驟 18
3-1試片表面前處理18
3-2製程條件18
3-3微結構觀察21
3-3-1掃描式電子顯微鏡21
3-3-2橫截面穿透式電子顯微鏡21
3-3-3能量散佈光譜儀22
3-4表面成分分析22
3-4-1低掠角X-ray繞射分析22
3-4-2化學分析電子光譜22
3-5化成皮膜抗蝕性質分析23
3-5-1極化曲線23
3-5-2鹽霧試驗23
第四章 實驗結果27
4-1AZ91D鎂合金底材分析27
4-1-1ICP-AES化學成分分析27
4-1-2表面形貌SEM觀察27
4-2不同酸洗前處理條件之試樣表面分析28
4-2-1表面顏色觀察28
4-2-2表面形貌SEM觀察28
4-2-3低掠角X-ray繞射分析29
4-2-4橫截面TEM觀察34
4-2-5表面ESCA分析39
4-2-5-1 11wt% HF酸洗處理後表面ESCA分析39
4-2-5-2 0.5wt% HNO3酸洗處理後表面ESCA分析46
4-3不同前處理件下試樣表面化成皮膜分析50
4-3-1表面形貌SEM觀察50
4-3-2橫截面SEM觀察51
4-3-3低掠角X-ray繞射分析51
4-3-4橫截面TEM觀察57
4-3-5極化曲線57
4-3-6鹽霧試驗58
第五章 討論64
5-1酸洗前處理對AZ91D底材造成影響64
5-2酸洗前處理對錫酸鹽皮膜成核影響65
第六章 結論67
參考文獻69



圖2-1 鎂的Pourbaix Diagram5
圖2-2 鎂鋁合金平衡相圖10
圖3-1 實驗流程圖20
圖3-2 橫截面TEM試片製作流程圖24
圖3-3 各種成分分析儀器的穿透深度比較25
圖3-4 鹽霧試驗裝置示意圖26
圖4-1 AZ91D表面形貌：(a)低倍率觀察顯示β相以及缺陷分佈；
(b)高倍率局部區域放大觀察28
圖4-2 經過酸洗前處理後試片表面色澤：(a)11wt% HF；(b)0.5wt% HF；(c)0.5wt% HNO3；(d)0.5wt% HCl30
圖4-3 酸洗前處理20秒後表面形貌觀察：(a)11wt% HF；(c)0.5wt% HF；(e)0.5wt% HNO3；(g)0.5wt% HCl，(b),(d),(f),(h)分別為(a),(c),(e),(g)的局部放大31
圖4-4AZ91D鎂合金底材GA-XRD圖譜32
圖4-5 11 wt% HF酸洗前處理後試樣表面GA-XRD圖譜32
圖4-60.5 wt% HNO3酸洗前處理後試樣表面GA-XRD圖譜33
圖4-7 11wt% HF酸洗前處理後橫截面TEM觀察：(a)鈍化膜形貌；(b)鈍化膜的擇區繞射分析35
圖4-8 圖4-7(a)中鈍化膜的EDS成分分析35
圖4-9 0.5wt% HF酸洗前處理後橫截面TEM觀察36
圖4-10 圖4-9中鈍化膜的EDS成分分析36
圖4-11 (a)0.5wt%HNO3酸洗前處理後橫截面TEM觀察；(b)為鈍化膜的擇區繞射分析；(c)為(a)的局部放大37
圖4-12針對圖4-11(c)中特徵微結構之EDS量測(a)點1(b)點2 38
圖4-12針對圖4-11(c)中特徵微結構之EDS量測(c)點3 39
圖4-13 11wt% HF酸洗處理後表面之元素縱深分析 41
圖4-14 11wt% HF酸洗處理後表面Mg2p的圖譜，分析位置分別為轟擊時間：(a)2min；(b)5min；(c)10min 42
圖4-15 11wt% HF酸洗處理後表面O1s的圖譜，分析位置分別為
轟擊時間：(a)2min；(b)5min；(c)10min 43
圖4-16 11wt% HF酸洗處理後表面F1s的圖譜，分析位置分別為轟擊時間：(a)2min；(b)5min；(c)10min 44
圖4-17 11wt% HF酸洗處理後表面Al2p的圖譜，分析位置分別為轟擊時間：(a)2min；(b)5min；(c)10min 45
圖4-18 0.5wt% HNO3酸洗處理後表面之元素縱深分析 46
圖4-19 0.5wt% HNO3酸洗處理後表面Mg2p的圖譜，分析位置分別為轟擊時間：(a)2min；(b)5min；(c)10min 47
圖4-20 0.5wt% HNO3酸洗處理後表面O1s的圖譜，分析位置分別為轟擊時間：(a)2min；(b)5min；(c)10min 48
圖4-21 0.5wt% HNO3酸洗處理後表面Al2p的圖譜，分析位置分別為轟
擊時間：(a)2min；(b)5min；(c)10min…………………………...49
圖4-22 30秒化成後的表面形貌：(a)未前處理；(c)11wt% HF前處理；(e)0.5wt% HF前處理；(g)0.5wt% HNO3前處理，(b),(d),(f),(h)分別為(a),(c),(e),(g)的局部放大 52
圖4-23 60秒化成後的表面形貌：(a)未前處理；(c)11wt% HF前處理；(e)0.5wt% HF前處理；(g)0.5wt% HNO3前處理，(b),(d),(f),(h)分別為(a),(c),(e),(g)的局部放大 53
圖4-24 10分鐘化成後的表面形貌：(a)未前處理(c)11wt% HF前處理；(e)0.5wt% HF前處理；(g)0.5wt% HNO3前處理，(b),(d),(f),(h)分別為(a),(c),(e),(g)的局部放大 54
圖4-25 不同酸洗條件化成10分鐘進行橫截面SEM觀察(a)未前處理；(c)11wt% HF；(e)0.5wt% HF；(g)0.5wt% HNO3；(b),(d),(f),(h)分別為(a),(c),(e),(g)的局部放大 55
圖4-26 11 wt% HF酸洗前處理後化成10分鐘之試樣表面GA-XRD圖譜56
圖4-27 0.5wt% HNO3酸洗前處理後化成10分鐘之試樣表面GA-XRD圖譜56
圖4-28 11wt% HF酸洗後化成60秒之橫截面形貌：(a)大範圍之橫截面形貌；(b)為(a)箭頭處之局部放大；(c)為(b)之底材部分之延伸59
圖4-29 0.5wt% HNO3酸洗後化成60秒之橫截面形貌：(a) 大範圍之橫截面形貌；(b)為(a)底材凹陷處之局部放大；(c)為(a)箭頭處之放大60
圖4-30 經酸洗前處理並經化成處理10分鐘之極化曲線61
圖4-31 酸洗後化成處理10分鐘之試樣未經鹽霧試驗外觀，酸洗前處理條件為：(a)未前處理；(b)11wt% HF；(c)0.5wt% HF；(d)0.5wt% HNO3；(e)0.5wt% HCl62
圖4-32 酸洗後化成處理10分鐘之試樣經過鹽霧試驗後外觀，酸洗前處理條件為：(a)未前處理；(b)11wt% HF；(c)0.5wt% HF；(d)0.5wt% HNO3；(e)0.5wt% HCl63


表2-1 ASTM結構用鎂合金的表示方式6
表2-2 各種元素的標準還原電位7
表2-3 Dow 化學公司各種鉻酸鹽皮膜處理成份17
表3-1 本研究之酸洗液配置參數19
表3-2 本研究之化成溶液配置參數19

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