Preparation And Properties Of Water-borne On-rust Coating Based On 1-pentyl Gallate

Water-based rust coatings are environmentally friendly,non-toxic and non-flammable,and are increasingly used in the rust treatment of steel components.Traditionally,rust coatings use gallic acid or phosphoric acid derivatives as the main conversion agent,which have the disadvantages of insufficient rust conversion ability and poor stability.Therefore,it is of practical importance to develop a water-based rust coating that can overcome the above-mentioned shortcomings.In this paper,n-pentyl gallate was first synthesized from gallic acid and n-pentanol,and the rust converter was made with n-pentyl gallate,isopropanol,acetic acid,and water.The optimal reaction condition of the synthesis reaction was determined,and the rust conversion effect was studied.Meanwhile,the rust conversion and rust prevention effects of 1-alkyl gallate and gallic acid with different side-chain lengths,such as methyl gallate,ethyl gallate,propyl gallate,butyl gallate and pentyl gallate,were investigated as rust converters.By analyzing the composition and surface morphology of the rust converter film,the results showed that the increase in the length of side chains could increase the cross-linking between molecules to form a more complete surface of the rust converter film.The electrochemical properties of the rust conversion film were further investigated by electrochemical means such as electrochemical polarization and electrochemical impedance spectroscopy,and the results showed that increasing length of the carbon chain of gallate can result in higher electrochemical impendence.Based on the above comprehensive characterization,n-pentyl gallate has advantages over other side chain based gallates and can be used as the main rust converter component for subsequent research.Secondly,this paper explored the application of electrochemical noise method in rust transfer and rust prevention.The above corrosion noise signals were characterized by exploring the characteristics of corrosion noise signals under different electrolyte conditions,such as statistical information,wavelet analysis information,and recurrence plot information.The electrochemical noise parameters were classified by linear discriminant analysis,and the classification matrix was then applied to the fitting of initial conditions for the conversion agent concentration in the rust converter.The optimal initial conditions obtained from the fitting were combined with designed orthogonal experimental and the salt spray resistance of different formulations by means of salt spray test,etc.The optimal rust conversion system ratios were obtained with 1-pentyl gallate as the main conversion agent:20%gallate,9%polyphosphate,2%polyethylene glycol,30%isopropanol by mass,and the rest was water,which could prevent rust under neutral salt spray test for 504 h.Finally,this paper investigated the formulation of primers for rust conversion systems based on 1-pentyl gallate.The optimal film-forming additives were obtained by examining the mechanical properties of the paint film such as adhesion and impact resistance under different compositions.The optimum composition of talc 7.5%by mass and the precipitation of barium sulfate 12.5%by mass was determined by studying the water absorption of the paint film with different compositions.The optimal ratios of the remaining components in the color filler were obtained by orthogonal experimental design:5%by mass of iron oxide red,12%by mass of aluminum tripolyphosphate and 6%by mass of zinc phosphate.At the optimum concentration of rust converting agent,the prepared waterborne rust-belt coating has 0-level coating adhesion,1 mm flexibility,50/50(kgf·cm)front and back impact resistance,and salt spray resistance up to 480 h.