The Development Of Carbon Steel Inhibitor In Citric Acid Solution

The carbon steel is the earliest and most widely used basic materials in modern industry,such as the application in the Chemical industry, Oil pipeline, Electricity, etc. The equipmentof carbon steel used for a long time will produce scale, rust scale and other sediments,pickling is an effective cleaning methods. In order to reduce the consumption of acid solutionand the corrosion of metal, need to add the appropriate corrosion inhibitor in the solution.Now, the research of pickling solution at home and abroad is a lot, but hydrofluoric acid andsulfuric acid exist defects of corrosivity strong and volatile. Citric acid is a kind of relativelyweak acid, the rate of circulation is fast when it is pickling. The corrosion inhibitor of citricacid has prominent features of simple and safe operation, less dosage, high corrosion rate,stable performance, non-toxic and pollution, etc, so the research of corrosion inhibitor in citricacid is very meaningful. In the process of chemical cleaning, by reducing the corrosion rate,itcan restrain the occurrence of the hydrogen embrittlement and the corrosion of Fe3+on metal,furthermore, prevent the metal from pitting corrosion.Firstly a large number of organic and inorganic compounds were filtered by theweight-loss method. The results showed that several compounds have better corrosioninhibition efficiency in3%citric acid solution. They are thiourea,1,2,3-BTA (Benzotriazole),CPB (Cetylpyridinium Bromide). The three kinds of compounds above were considered asone-component object to study, respectively were measured by the weight-loss method andelectrochemical polarization curve method. Which is to present the corrosion inhibition effectof one-component inhibitor of carbon steel in3%citric acid solution under differentconditions, and get the corresponding thermodynamic data. Then, make the correspondingweightlessness curve, the adsorption isotherm and the change curve of adsorption coefficientand temperature, etc. The experimental results showed that the three compounds in the surfaceof carbon steel were monolayer adsorption, and conform to Langmuir adsorption rule.Secondly on the basis of the experimental results of one-component screening,orthogonal experiments were performed with various kinds of compounds by usingorthogonal experiment method, which is to get a compound corrosion inhibitor with bettereffect. Moreover, the performance of the compound corrosion inhibitor were analyzed andmeasured by various experimental methods like weight-loss method, electrochemicalpolarization curve analysis and scanning electron microscopy. Finally through a variety ofexperimental methods, the relationship between corrosion rate of carbon steel and concentration of compound corrosion inhibitor under different temperature, and therelationship between compound corrosion inhibitor and time, temperature, and acidconcentration were analyzed. The conclusion is that the compound corrosion inhibitor madeby compound experiments is a good kind of carbon steel corrosion inhibitor in citric acidmedium.