Corrosion-resistant coating of reinforcing stell for marine concrete and preparation method therefor

A preparation method for a corrosion-resistant coating of a reinforcing steel for marine concrete, comprising the steps:

• (1) pretreating a surface of the reinforcing steel;
• the reinforcing steel is ready to be used after a deoiling step, a acid pickling step, a water washing step and a sandblasting step;
• (2) preparing a self-repairing corrosion microcapsules, comprising the steps:
• (a1) adding urea in 10-12 weight portions, formaldehyde in 18-20 weight portions and ammonium chloride in 1-3 weight portions into an reactor, adding a pH regulator to adjust the pH value to 8-10, a temperature rises to 60° C.-80° C. after being stirred evenly, an urea-formaldehyde resin prepolymer is formed by a reflux reaction for 2-3 hours;
• (b1) stirring for 10-15 minutes at a temperature of 50° C.-60° C. after mixing resorcinol in 5-10 weight portions, polyvinyl alcohol in 3-7 weight portions, linseed oil in 10-20 weight portions, 2-phenylbenzimidazole in 1-3 weight portions, emulsifying for 20-30 minutes to form an oily emulsion after adding 1-5 parts of deionized water and 0.1-0.5 parts of sodium dodecylbenzene sulfonate;
• (c1) adding the urea-formaldehyde resin prepolymer obtained in step (a1) into the oily emulsion in step (b1), the pH value is adjusted to 3-4 with hydrochloric acid, the reflux reaction is carried out at 70° C.-90° C. for 2-3 hours, the obtained product is vacuum filtered, washed with deionized water and acetone, and dried in a drying oven to obtain a self-repairing corrosion microcapsules;
• (3) preparing a cathodic electrophoretic coating,
• (a2) by weight, adding 5-10 parts of 2,4-toluene diisocyanate and 20-30 parts of propylene glycol methyl ether into a reaction kettle, after stirring and raising the temperature to 50° C.-60° C. under a protective atmosphere, dripping 3-5 parts of methyl isobutyl ketone within 2-3 hours, after completion, it is heated again to 110° C.-120° C. for reaction lasting for 2-3 hours, and the content of NCO group is measured to obtain a semi-blocked isocyanate;
• (b2) in a reaction bottle equipped with a thermometer, a stirrer and a reflux condenser tube, 50-60 parts of water-based hydroxyacrylic resin, 10-30 parts of semi-closed isocyanate are added in turn, it is stirred and raised to 40° C.-60° C., and 2-5 parts of acetic acid, 1-5 parts of metal powder, 1-5 parts of graphene oxide powder, 5-10 parts of isopropanol and 10-30 parts of deionized water are added, then continue to stir for 10-20 minutes to prepare a colorant;
• (c2) 30-50 parts of organic amine modified epoxy resin, 2-10 parts of diethylene glycol butyl ether, 5-15 parts of bisphenol A polyoxyethylene ether, 1-5 parts of methyl isobutyl ketone, 10-20 parts of semi-blocked isocyanate and 20-30 parts of deionization are mixed evenly to obtain a lotion with solid content of 30-50%;
• (d2) the colorant and the lotion is mixed in proportion of (1:2)-(1:4), then 1-5 parts of deionized water is added, stirred and matured evenly for 24-48 hours;
• then 5-10 parts of self-repairing corrosion microcapsules are added and stirred for 10-30 minutes to the obtain cathodic electrophoretic coating, and then the cathodic electrophoretic coating is put into a cathodic electrophoretic tank;
• (4) cathodic electrophoresis:
• placing the reinforcing steel in the cathodic electrophoresis tank, the process parameters of the electrophoresis are set as follows:
• the solid content of a tank liquid of the cathodic electrophoresis is 10%-15%, the pH value is 5.5-6.5, the conductivity is 200-500 us/cm, the temperature of the tank liquid is 30° C.-50° C., the electrophoresis voltage is 50-100V, and the electrophoresis duration is 3-10 minutes;
• (5) curing:
• moving the electrophoresed reinforcing steel into the drying oven, at the temperature of 150° C.-200° C., and the duration for 20-40 minutes, and then cool it naturally.