Corrosion Inhibition Performance Of Green Inhibitors And Melamine Derivatives For Mild Steel In Acid Solution

Mild steel is a kind of primary metallic materials,and is widely used in defense industry,electronics,chemicals,machinery,construction,transportation,and so on.However,mild steel is inevitably subject to some degree of corrosion in the environment in which it is located,especially in the pickling industry.There are H~+and Cl~+in HCl solution,which will interact with lively elements in mild steel,leading serious corrosion.Therefore,the protection of mild steel has always been the concern of researchers.Among the methods for corrosion inhibition,adding corrosion inhibitors is an effective,simple and economical corrosion inhibition method,which is widely used in the industrial field.Corrosion inhibitor molecules with N,O,P,S and some other elements with large electronegativity,will enable the corrosion inhibitor to be strongly adsorbed to the metal surface,preventing metal from corrosion.However,some organic molecules will do harm to environment and human body.With the enhancement for people’s awareness of environmental protection,the development of environmentally friendly and highly efficient corrosion inhibitors has become an important issue in the field of corrosion inhibition today.Developing environmentally friendly corrosion inhibitors not only hinder the corrosion of metals but also do not destroy ecosystems.The research contents of this paper can be divided into two parts:In the first part,the corrosion inhibitions of several melamine derivatives at the same concentration were compared,and the effects of substituent chain length and number on corrosion inhibition performance of corrosion inhibitors were explored.Combining experiments and theoretical calculations,the relationships between corrosion inhibitions and molecular structures,as well as the adsorption configurations and corrosion inhibition mechanisms of corrosion inhibitor on metal surface were explored.The second part,some cheap,non-toxic,non-polluting materials were explored as corrosion inhibitors for the corrosion of mild steel.And there inhibition performances were investigated by experiments,the mechanisms of corrosion inhibition was studied by other means of characterization.The main research contents are as follows:Part 1:Relationship between inhibition performance of melamine derivatives and molecular structure for mild steel in acid solution.The influence of substituent groups on the inhibition performance of the heterocyclic ring is attractive in the field of corrosion inhibitor.The modification of various polar functional groups including dimethylamino ethyl and dimethylamino propyl groups on melamine ring can endow these compounds with good water solubility and even high corrosion inhibition efficiency.The inhibition properties of five functional melamine compounds with methyl and different numbers of tertiary amino groups were investigated electrochemically and theoretically.The inhibition mechanisms of these inhibitors for mild steel in acid solution and the relationship between their inhibition performances and molecular structures are also discussed.Part 2:Application of a cosmetic additive as an eco-friendly inhibitor for mild steel corrosion in HCl solution.The use of the cosmetic ingredient cocamidopropylamine oxide(CAO)to inhibit the corrosion of steel in 0.5 mol/L HCl is investigated.Electrochemical and weight loss methods were used to evaluate the inhibiting effect of CAO and the influences of inhibitor concentration and temperature were determined.It was found that CAO acted as a mix-type inhibitor and was adsorbed chemically onto the steel in HCl solution,and the maximum inhibition efficiency was found at critical micelle concentration(CMC)of CAO in tested corrosive media.Moreover,it was speculated that relationships of the two adsorption sites of the inhibitor and steel surface were different.Part 3:Longan seed and peel as environmentally friendly corrosion inhibitor for mild steel in acid solution.Longan seed and peel were extracted and used for impeding the corrosion of mild steel in hydrochloric acid solution.Experimental analyses indicate that the water extract of Longan’s seed and peel,a mixed type inhibitor,can be chemically adsorbed onto the steel surface,and its inhibition effect rises with increasing extract concentration.To understand the adsorption mechanism and the contributions of the four main compounds of the extract to corrosion protection effect,quantum chemical methods and infrared spectrum were also employed.Theoretically,four main antioxidant compounds were regarded as effective components in the water extract of Longan’s seed and peel.