硼酸盐缓蚀作用机理的研究——对缓蚀过程中溶解氧作用的新见解

采用腐蚀失重法、电位-时间曲线、极化曲线、划伤电极技术、赤血盐显色试验及XPS等方法,研究了硼砂对碳钢的全面腐蚀与孔蚀的缓蚀作用与机理。结果发现,硼砂对碳钢的缓蚀作用并不依赖于溶解氧的存在,而且随溶解氧浓度的增加.其缓蚀率、抗孔蚀及Cl~-侵蚀的能力,以及膜的修复能力下降。在有溶解氧存在的条件下,硼砂在碳钢表面所形成的保护膜的主要组成是FeO、Fe2_O_3与铁的硼酸盐,并夹杂有Cl-,硼砂表现出阳极抑制型缓蚀剂的特性;在脱氧的条件下.膜的主要组成是在微薄的FeO、Fe_2O_3膜上吸附B_4O_1~(2-)离子,硼砂表现出混合抑制型缓蚀剂的特征。

ON THE EFFECT OF DISSOLVED OXYGEN ON THE CORROSION INHIBITION OF CARBON STEEL WITH BORAX

Corrosion weight loss test, corrosion potential-time curve, polarization curve, scratched electrode technique and colour test with K_3Fe(CN)_6 and NaCl solution etc. have been used to investigate the inhibition effect of borax on carbon steel in deionized water, FeCl_3 and KClO_3 solutions with different conditions of aeration. The chemical composition of the inhibitory film has been analysed by XPS. It is found that the inhibition of borax is independent on the existence of dissolved oxygen in the solutions. As the concentration of dissolved oxygen increase, the inhibition efficiency, the resistance to pitting perforation of Cl~- and the ability to repair the inhibitory films decrease. The inhibitory films formed by borax on the surface of carbon steel in FeCl_3 solution with dissolved oxygen mainly consists of Fe_2O_3, FeO and ferric borate, with occluded Cl~- ions. In this case, the borax acts as an anodic inhibitor. Under fully deaerated condition, however, the inhibitory film consists of FeO, Fe_2O_3 and adsorbed B_4O_7~(2-) ions, and the borax acts as a mixing inhibitor.