Chlorophyll and pheophytin: experimental aspects of corrosion regulation

Abstract

The introduction indicates the object of research – natural porphyrin chlorophyll and its derivative pheophytin, as possible inhibitors of steel corrosion. Modern, reasoned data on the structure and physico-chemical properties of chlorophyll, such as aromaticity, chelate effect, amphotericity, ability to redox transformations are presented. The basic concepts are defined: porphyrin, pheophytin, aromaticity, pyrrole nitrogen, complexing ability, acidophobia, diphilicity of porphyrin and pheophytin, mass and volume corrosion indicators, corrosion inhibitor, degree of protection, inhibition coefficient. The aim of the research was to study the anticorrosive activity of chlorophyll and its derivative, pheophytin, in relation to carbon steel St3. The main part describes a method for extracting chlorophyll from the leaves of nettle dioecious (Nettle dioecious L.) and the subsequent production of feofitin from it. The methods of determining the mass and volume indicators of the corrosion rate are described. The absence of pronounced anticorrosive activity of chlorophyll in relation to carbon steel St3 in hydrochloric acid medium is shown. The effect of absorption by chlorophyll of hydrogen released at the cathode is demonstrated, which makes the use of a volumetric corrosion rate indicator vulnerable under these conditions. It was found that the pheophytin layer deposited on the metal surface exhibits an inhibition effect under conditions of acid and atmospheric corrosion. The inhibitory effect of feofitin (4,4) was established during 96 hours of exposure with subsequent damping dynamics in the experiment with 3M HCl. Under the influence of feofitn, an elongation of time was observed before the appearance of visible foci of atmospheric corrosion. Studies of the efficacy of porphyrins as corrosion inhibitors should be supplemented by the results of the long-term effects of these compounds.