Development And Performance Study Of A Nearly Neutral Rust Remover For Steel Material

Steel materials are widely used in variours industries.However,large amounts of rust are easily grown on the substrate and need to be removed due to corrosion.At present,strong acid pickling is the main method to remove rust.Although the cost is low and the removal rate is fast,there are many disadvantages,for example,the solution is harmful to the operator,the substrate after treatment with rust remover is severely corroded,and it has lots of damage to the environment.In order to solve problems brought by acid pickling and achieve the needs of industry,this thesis aims to develop a formula that can remove rust in a nearly neutral environment.In this thesis,Q235 carbon steel was used as the research material,rusty specimens immersed in simulated marine environment were used as the rust removal object.Rust removal rate of the formula with different ingredients was studied and compared by weight loss method under 25℃ water bath.A nearly neutral rust remover formula with good rust removal rate was developed.The rust removal rate of the formula under different experimental conditions was also discussed,and the technical indicators of the the nearly neutral rust remover was tested.Macroscopic observation,metallographic microscope observation,Fourier transform infrared spectrometer,X-ray photoelectron spectroscopy analysis were used to compare the substrate of the specimen before and after treatment with the nearly neurtal rust remover.This thesis also compares the performance of the experimentally prepared nearly neutral rust remover with the strong acid pickling solution,and the commercially available neutral rust remover in terms of rust removal rate and corrosion rate.Besides,the rust removal mechanism of the nearly neutral rust remover is proposed.The research results of this thesis are as follow:(1)The main ingredients of the nearly neutral rust remover formula developed by weight loss method include:citric acid 100 g/L,etidronic acid 100 g/L,isopropanol 25 g/L,zinc acetate 2.5 g/L,sodium molybdate 7.2 g/L,chelating agent A 4.5 g/L,surfactant A 5.0 g/L,and other ingredient is deionized water.Adjust pH to 6.0 with sodium hydroxide.(2)For moderate rust on Q235 carbon steel,the rust removel rate of the nearly neutral rust remover is 200～250 g/m2·h under 25℃ water bath,and 1kg rust remover can deal with 7.5 g～8.0 g rust.(3)The performance of rust removal ability and corrosion ability of the nearly neutral rust remover prepared in the experiment was compared with two strong acid pickling solutions and a commercially available neutral rust remover.The rust removal rate of the nearly neutral rust remover is slower than those pickling solutions,and faster than the commercially available neutral rust remover.The corrosion rate of the nearly neutral rust remover is lower than those pickling solutions,and is close to the commercially available neutral rust remover.(4)Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy analysis were used to analyze the rust removal mechanism of the nearly neutral rust remover.Two organic acids are ionized in the solution,O on the oxygen-containing functional group has lone-pair electron,while the highvalent iron on the rust has an empty orbital.Fe accepts the lone-air electron of O to form a coordination bond,which can clean up rust at nearly neutral condition.Some of the reaction products enter the solution,and the other products adsorb on the substrate,and provide protection to the substrate.