硝酸鹽和亞硝酸鹽對碳鋼抗蝕性之影響

The Effects of Nitrate and Nitrite on Corrosion Resistance of Carbon Steel

本計畫分為兩部份：(1)硝酸鹽對碳鋼抗蝕性之影響；(2)亞硝酸鹽對鋼抗蝕性之影響。動電位極化法將用以研究之，另以重量損失（改變）法作為核對之用。實驗參數計有：(1)硝酸鹽或亞硝酸鹽之濃度；(2)氯化鈉或鉻酸鈉之濃度，(3)溶劑（水或異丙醇）之種類；溶液之酸鹼度；(4)溶液之酸鹼度。由動電位極化腐蝕所得數據，使用本實驗室所發展之REDIF微電腦程式以計算腐蝕電流密度，極化電阻，和鐵弗爾常數。有關金屬腐蝕型態或鈍化膜之觀察可使用立體顯微鏡為之。由實驗所得之結果，我們提出(1)硝酸鹽或亞硝酸鹽的抗蝕機理。(2)異丙醇所扮演之角色。(3)腐蝕速率異常之解釋。

The project includes two parts: (1) the effect of nitrate on the corrosion resistance of carbon steel and (2) the effect of nitrite on the corrosion resistance of carbon steel. The potentiodynamic polarization technique along with weight loss method are used in this study. The experimental parameters include: (1) the concentraions of nitrate or nitrite; (2) the concentrations of sodium chloride or sodium chromate, (3) the type of solvents (water or isopropyl alcohol); and (4)the pH of the solution. The corrosion data obtained from potentiodynamic polarization are input into the REDIF microcomputer program developed in this laboratory to calculate the corrosion current densities, polarization resistance, and Tafel constants. The corrosion patterns of metal or the passive film were observed by stereo-microscope. From the experimental results, we would (1) suggest the anticorrosion mechanisms of nitrate or nitrite; (2) determine the role of isopropyl alcohol, and (3) suggest the causes of the abnormal pattern of the corrosion.