Effect Of Pigments On Properties Of Aicohoi-soiuble Inorganic Zinc-rich Coating

The effects of replacing 5, 10, 15, 20, 25 and 30wt% of spherical zinc pigments inalcohol-soluble inorganic zinc-rich coating with lamellar shaped zinc pigments,aluminum, graphite, Fe2P, ZnO, talcum powder and high titanium powder respectively onperformances of the coatings were studied in this thesis. Physical properties of thecoatings such as adhesion, thickness were tested. Anti-corrosion properties of thecoatings were evaluated by means of salt spray test and whole-dip in salt test. Corrosionbehavior of the coatings were studied by means of polarization curves(tafel), open circuitpotentials curves (OCP) and electrochemical impedance spectroscopy (EIS).Experimental results showed that the varieties and replacing ratios of pigments haslittle effect on the physical properties of the coatings. For lamellar shaped zinc pigments,aluminum, graphite, Fe2P, ZnO, talcum powder and high titanium powder, lives of thecoatings in salt spray versus the replacing ratio have the similar changing rule, namely,lives were prolonged firstly, then shortened, lives reached their maximum value at 20%,15%, 15%, 20%, 15%, 10%, 20% respectively. For the certain pigment, its life in NaClsolution versus replacing ratio has the similar changing rule and the same optimumreplacing ratio with its life in salt spray test.It was revealed that anodic process of coatings with replacing pigment in NaClsolution was inhibited obviously. In OCP test, the excellent property of coatings atoptimum replacing ratio in salt solution was found coming from its excellentperformance of cathodic protection. The following results were educed from EIS: forconductive pigment, electric resistance of coatings before immersion decreased withreplacing ratio firstly, then increased, it reached its minimum at its optimum replacingratio; for non-conductive pigment, electric resistance of coatings before immersionincreased with replacing ratio; double-layer capacitance value for the seven kinds ofpigment-replacing coatings at their respective optimum replacing ratio was aboutone-tenth the value for non-replacing coating after 1d immersion.