| Effects of dosage of zinc powder, addition of graphite powder and the morphology ofzinc powder on the cathodic protection performances of alcohol-soluble inorganic zincrich paints (ZRP) were studied and the effects of zinc content in a variety of factors oncathodic protection performances were analyzed in this thesis. Cathodic protectionperformances of ZRP coatings were evaluated by means of open circuit potential (OCP)method. Conductive adhesive electrochemical impedance spectroscopy (CAEIS) methodwas used to evaluate ZRP coatings’ dry film electrical conductivity. Self-designedgalvanostatic dissolution (GD) test was used to evaluate anodic dissolution performancesof ZRP coatings and the results were compared with the results from OCPmethod.Cross-section morphology of the coatings were observed by means of scanningelectron microscope(SEM).Experimental results showed that higher the zinc content is, longer the cathodicprotection duration is when the zinc powders applied were same in morphology and nographite pigments were added into the paint. This rule was broken when graphite pigmentswere added or zinc powder in different morphology were used in preparing paint. Afteradding graphite pigments the cathodic protection duration of ZRP coatings with zinccontent of72.5wt.%increased to120h which is longer than the duration of ZRP coatingwith zinc content of85.9wt.%. Zinc powders from Beijing and Tianjin were both in theprimary level and their particle size were500mesh, the zinc content of ZRP using Tianjinpigments was94.9wt.%, which was higher than the zinc content of ZRP using Beijingpigments (81.4wt.%). While the cathodic protection duration was576h for the coatingwith Tianjin zinc powders, which is shorter than the coating with Beijing zincpowder(1440h).It was disclosed that certain correlations existed both between CAEIS results, GDresults and OCP result. When the cathodic protection duration is shorter than100h, boththe dry film impedance and OCP in CAEIS method reduced with the increase of cathodicprotection duration, while when the cathodic protection duration is longer than100h, thedry film impedance was closed to105, and the OCP values in CAEIS method wereabout0V. Positive correlation relationship was found between active dissolution time inGD method and cathodic protection duration in OCP method when none graphitepigments were involved in and single kind of zinc pigment was used. |
