炔醇類有機物對低碳鋼高溫酸洗腐蝕之抑制作用

Inhibition of Steel Corrosion in 2 M HCl at 85 ℃ by Acetylenic Alcohols

本論文在探討使用炔醇類有機物作為碳鋼酸洗液（85℃之2 M HCl）抑制劑之可行性，研究採用重量損失法、極化阻抗法、直流電鐵弗極化法（Tafel Polarization）等方法進行評估，並輔以化學分析電子光譜儀（ESCA）解析抑制劑在鋼鐵表面之吸附行為。研究結果顯示：化學結構上影響炔醇類抑制效率之因素有三：（1）緊鄰C≣C三鍵之碳鏈長度增加，腐蝕抑制效率增加。（2）若C≣C三鍵位於炔醇結構末端，其腐蝕抑制效率較高。（3）在C≣C三鍵上銜接一苯環或氫氧基時，其抑制效率（分別為78.7%、78.6%）高於鍵結一單純之乙基碳鏈（57.0%）。由直流電化學的研究得知炔醇類在此酸洗環境下屬於陰極型抑制劑。酸洗後鋼片之表面，經Ar+離子濺渡蝕刻30秒後，由ESCA分析Fe 2p 3/2顯示：經含高效率抑制劑（2-Propyn-1-ol與2-Nonyn-1-ol）酸洗後之鋼片表面含零價之金屬鐵，而低效率抑制劑酸洗後之鋼片表面，則含氧化鐵，據此推測酸洗過程中抑制劑有效吸附於鋼材表面使其較不易被氧化之作用。

Acetylenic alcohols were used to inhibit the corrosion of low carbon steels in a pickling solution (i.e., 2 M HCl at 85 ℃). Results from coupon tests of weight-loss measurement and electrochemical analyses (including polarization resistance and Tafel extrapolation) were used to estimate the corrosion rate of the steels and the inhibitive efficiency of the inhibitors. The inhibitive efficiency (η) of the acetylenic alcohols was found to depend on their chemical formulae: (1) η increases with increasing number of carbon chains linked to the C≡C triple bond. (2) η is higher for the alcohols with a terminal C≡C triple bond than that with an internal one. (3) Substitution of the -CH3 in 2-Butyn-1-ol with the -CH2OH group (i.e., 2-Butyn-1,4-diol) by a benzene ring (-C6H5) (i.e., 3-Penyl-2-propyn-1-ol) increases the η. A negative shift of the corrosion potential caused by the addition of acetylenic alcohols implied that these alcohols are cathodic inhibitors. The activation energies were estimated to be 105.9 and 90.4 kJmol-1 according the Arrhenius plot in the absence of the inhibitors and in the presence of 2-butyn-1-ol, respectively. A lower activation energy in the presence of 2-butyn-1-ol inferred a chemisorption of this species on the steels. The adsorption of acetylenic alcohols obeyed the Langmuir adsorption isotherm. After a sputtering of 3 keV Ar+ for 30 s for surface oxide removal, the steels pickled in solutions with and without the inhibitors were analyzed by ESCA. The ESCA analysis on Fe 2p 3/2 indicated that metallic irons were present on the surface of the inhibited steels whereas iron oxides on that of the poorly inhibited ones. It is therefore speculated that the adsorption of the inhibitors on the steel surface to inhibit corrosion of the steels.