The Resistance Mechanism Of Amino Alcohol Corrosion Inhibitors In Acid Rain

Currently reinforced steel concrete is the most commonly used building structures,the reinforced steel is not easy to damage by corrosive ions because reinforced steel can form passivation film under the pH close to 12.6 in pore solution in concrete.With the development of the industry,acid rain has become more popular especially industrial zone,reinforced steel has corroded by serious acid rain with service time of concrete structure prolonged.Many methods used to prevent reinforced steel to be corroded,such as coatings,cathode protection,increasing the compactness of concrete,corrosion inhibitor.It is widely used for corrosion inhibitor because simple,inexpensive etc.Amino alcohol corrosion inhibitors can control the anodic and cathodic process at the same time.It has the better performance in chloride environment and has received the widespread attention.Typical representative of corrosion inhibitors for this class is amino alcohol corrosion inhibitors,it can be divided into the internal mixing type for new project and the coating type for repairing project.Amino alcohol corrosion inhibitor has carried out a large amount of research by relevant scholars,but its research in acid environment is little,so the corrosive mechanism and performance of amino alcohol corrosion inhibitor in acid rain and chloride environment was researched in this article through the macroscopic observation,microscopic characterization and electrochemical method contrast to MFP.This experiment was initially judged the corrosion resistance effect through directly observed and calculated the corrosion area of carbon steel and steel surface.Then the microscopic characterization method was used for further judgment of corrosion resistance performance by using SEM and XRD directly to determine the carbon steel surface passivation membrane integrity and density,the density of mortar pore and the hydration products in the mortar.The electrochemical method was used in carbon electrodes and the reinforced concrete electrode to determine the charge transfer resistance,corrosion resistance etc.contrast to MFP under the addition of corrosion inhibitor in different media solution.The corrosive performance and mechanism of amino alcohol corrosion inhibitors in acid rain and chloride environment were comprehensively evaluated and drew the following conclusions through the experiment.1)On the one hand,amino alcohol corrosion inhibitors form the passivation membrane by promoting the steel surface to improve the steel surface activation energy and protect the reinforcing steel rebar,on the other hand,the coating corrosion inhibitor hinders the encroaching ion and media into the concrete by forming the deposits on the concrete surface;The internal corrosion inhibitor promotes concrete water forming gel material,adsorbing erosion ion and medium,and inhibiting the encroaching ion and media into the concrete.2)Both of them shown that the corrosion resistance performance of amino alcohol corrosion inhibitors were better than MFP,the coating corrosion inhibitor was the best among them through the experiments of direct observation,microscopic characterization and electrochemical impedance regardless of chlorine salt or acid rain environment in simulated pore solution.Liquid amino alcohol corrosion inhibitors are more likely to spread and merge with contacts compared with MFP powder no matter in simulated pore solution or mortar structure.The possible reason of coating corrosion inhibitor is the best one among them is that the specific functional groups or chelate can form a more homogeneous and stable passivation membrane.The coating corrosion inhibitor can form the white precipitate with cement material through functional groups or parts of chelating substances to stop the outside corrosive ions invading,and then it reach to the surface of the reinforced steel through the diffusion or capillary absorption;The XRD object analysis of the internal mixing corrosion inhibitor showed that the C3 S diffraction peak is incerased to prove that this type of corrosion inhibitor can promote the hydration of concrete,increase its density to prevent corrosive ions into effect;Both of them form a protective film after reaching to the surface of the reinforced steel and improve the density of concrete to prevent corrosive substances but also corrosion inhibitor into.The possible reason of the coating corrosion inhibitor has the better effect maybe that its ability of diffusion and capillary adsorption is strong to penetrate to the surface of reinforced concrete easier,and the more homogeneous and stable protective film can be formed to provide a more stable protection mechanism than the other corrosion inhibitor.3)The corrosion resistance performance of coating corrosion inhibitor is superior to the internal mixing corrosion inhibitor under the condition of chlorine salt environment in mortar structure,while the corrosion resistance performance of internal mixing corrosion inhibitor is better than the coating one in acid rain,and both of them are superior to MFP.Acid rain includes low pH,composite ion can change environment rapidly compared with a single chlorine salt environment to accelerate the reinforced steel depassivation.Therefore,corrosion inhibitor can provide better corrosion resistance effect in chlorine salt environment.The possible reason of internal mixing corrosion inhibitor can provide better performance is that sulfate and chloride salt coupling effect the migration of corrosion inhibitor.4)In chlorine salt environment,the corrosion resistance performance of the coating amino alcohol corrosion inhibitor is superior to the internal mixing amino alcohol corrosion inhibitor in the simulated concrete pore solution and concrete specimen.The corrosion resistance performance of coating amino alcohol corrosion inhibitor is superior to the mixing amino alcohol corrosion inhibitor in the acid rain,but the corrosion resistance performance ofmixing corrosion inhibitor is superior to the coating corrosion inhibitor in concrete specimen.The reason is that the water type corrosion inhibitor can react with carbon steel electrode surface quickly in simulated pore solution.The adsorption ability of coating amino alcohol to carbon steel surface is stronger than the internal mixing amino alcohol corrosion inhibitor,it can be more rapid and complete passivation film formation to protect the reinforced steel rebar.The coating corrosion inhibitor form the white precipitate on the concrete surface in chlorine salt environment in concrete specimen,it can directly inhibit the corrosive ions into the internal concrete.The coating amino alcohol corrosion inhibitor can reach to the reinforced steel rebar quickly through capillary absorption,evaporation compared with internal corrosion inhibitor.The hydrogen ions in acid rain combined with the alkaline matter in the concrete to reduce the pH,the acid rain in the sulfate and alkaline matter precipitation in concrete,although inhibits the corrosive substances to enter to a certain extent,but also inhibits the entry of corrosion inhibitor.There is a competitive relationship between the sulfate and chloride ions in acid rain in simulated pore solution,hydrated calcium aluminate will combine with chlorine ion and sulfate reacts with the rest of hydrated calcium aluminate,so the chloride ion can delay sulfate erosion,but reduces the pH and worsen the conditions of the reinforced steel surface passivation membrane.