Inhibition of corrosion of ASTM A192 steel in hydrochloric acid solution by the mucilage of Linum usitatissimum

ABSTRACT In this study, the inhibition of the corrosion of ASTM A192 steel in HCl 0,5 M at temperature different, by the Linum usitatissimum mucilage, was investigated using techniques: Tafel extrapolation, linear polarization resistance, electrochemical impedance spectroscopy and electrochemical frequency modulation. The Linum mucilage acts as an optimum corrosion inhibitor of ASTM A192 steel in HCl. The average inhibition efficiency obtained with the evaluated techniques were of 84,3% at 25 °C, 89,0% at 45 °C and 91,8% at 65 °C, with a concentration of the mucilage of 1 g/l. It was found that the efficiency of inhibition and the adsorption constant increased with increasing temperature. The standard enthalpy of adsorption was positive and the apparent activation energy decreased with the increase of the concentration of the mucilage. All these parameters indicate that the adsorption of flaxseed mucilage in steel evaluated occurs through a chemical adsorption. In addition, as the temperature increases, mucilage behavior changes from an anodic inhibitor to a mixed-type inhibitor.摘要 本研究采用塔菲尔外推法(Tafel extrapolation)、线性极化电阻法(linear polarization resistance)、电化学阻抗谱(electrochemical impedance spectroscopy)及电化学频率调制法(electrochemical frequency modulation)，探究了亚麻籽(Linum usitatissimum)粘液对不同温度下0.5 mol/L盐酸中ASTM A192钢的腐蚀抑制作用。该亚麻籽粘液可作为该体系中ASTM A192钢的高效腐蚀抑制剂。当粘液浓度为1 g/L时，采用上述测试方法得到的平均缓蚀效率分别为：25℃下84.3%、45℃下89.0%、65℃下91.8%。研究发现，缓蚀效率与吸附常数均随温度升高而增大。标准吸附焓为正值，且表观活化能随粘液浓度升高而降低。上述所有参数均表明，所测试的ASTM A192钢表面的亚麻籽粘液吸附过程属于化学吸附。此外，随着温度升高，该粘液的缓蚀行为从阳极型抑制剂转变为混合型抑制剂。