Высокотемпературная коррозия сталей в растворах кислот. Ч. 3. Ингибиторная защита сталей азотсодержащими гетероциклическими органическими соединениями и неорганическими окислителями. Обзор

Abstract

The literature and patent data on the protection of steels in high-temperature acid solutions by nitrogen-containing heterocyclic organic compounds and inhibitors of oxidative type were summarized. Composite inhibitors based on substituted triazoles can provide effective protection of low-carbon and chromium-nickel steels in these environments (200 °С). The mechanism of the protective action of these inhibitors is based on the ability of substituted triazoles to form on the steel surface in acid solutions the protective layers chemically bonded to the metal surface. Often these protective layers are basically composed of a polymer complex compound containing triazole molecules and Fe cations (in the case of nickel-chromium steels — Ni and Cr). It is noted that oxidizing additives can be used to protect steels which are in high-temperature acidic media at a passive state. Using the example of corrosion of chromium-nickel steel in H3PO4 solutions (130 °C), it is shown that additives of oxidants (Cu(II) and NO3–) stabilize the passive state of the metal in this medium, preventing the possibility of its active dissolution. Based on analysis of the literature data, a conclusion was made about the prospects of using compositions based on nitrogen-containing heterocyclic compounds for protecting steels in high-temperature acidic environments. These compositions are superior in important technological parameters to mixed inhibitors based on unsaturated organic compounds.