Preparation Of Waterborne Heavy-duty Epoxy Micaceous Iron Oxide Intermediate Coating And Study On Its Anticorrosion Performance

A kind of waterborne epoxy micaceous iron oxide coating with excellent corrosion resistance mainly used in heavy-duty field was prepared,and the factors influencing the anti-corrosion property were studied;The quick evaluation method of corrosion performance of waterborne epoxy micaceous iron oxide coating was also studied by electrochemical impedance spectroscopy(EIS),and the effects of intermediate coating on the anti-corrosion resistance of waterborne composite coatings were discussed as well.This paper includes several parts below.1.Preparing waterborne epoxy micaceous iron oxide coating: we studied the ratio of waterborne epoxy resin and curing agents,mica iron oxide pigment particle size and content,pigment volume concentration,kinds of wetting dispersants and its dosage,rheological agents,defoaming agents and their influences on the properties of coatings through traditional coating test methods,electrochemical impedance spectroscopy,scanning electron microscopy,infrared spectroscopy and so on.The results show that when choosing bisphenol A epoxy emulsion with medium epoxy equivalent as the membrane material and the molar ratio of epoxy and amine hydrogen is 1.2:1,adding micaceous iron oxide pigment of 600 mesh,and the content 63% of the pigment system,PVC 39%,the corrosion resistance of the coating is the best,and the physical and mechanical properties are also good.Choosing non-ionic polymer dispersant D as wetting and dispersing agent,the dosage 0.7%,bentonite M1 and anti-settling agent M3 as rheological additives,with the collocation use of silicone defoaming agent and mineral oil defoamer,coatings with good appearance and better comprehensive performance can be obtained.2.The failure behavior of waterborne epoxy micaceous iron oxide coatings was studied by electrochemical impedance spectroscopy,and the anti-corrosive properties of the coatings were also quickly evaluated.The results show that the coating resistance decreases rapidly at first,then decreases slowly,until the coating fails.The phase angle at 10 Hz and local fitting coating resistance can be used to quickly evaluate the coating performance and the changes in local fitting coating resistance and the phase angle at 10 Hz are almost same as that of coating resistance.The local fitting resistance reduces to 106Ω·cm2,and the phase angle at 10 Hz decreases to the range from 0 to 20 degrees,indicating that strong corrosion reaction had occurred in the substrate / coating interface and the diffusion behavior was obvious;The time that low frequency diffusion appears on the impedance spectrum of waterborne epoxy micaceous iron oxide coating is defined as electrochemistry failure time,which can shorten the macroscopic test time and accelerate the corrosion resistance detection of coatings.3.The effect of the thickness of the middle coating on the corrosion resistance of the waterborne composite coating was studied.The results show that the increase of intermediate coating thickness has obvious effect for improving the corrosion resistance of waterborne composite coatings.However,while determining the supporting system,the construction,cost and other factors should be taken into consideration.The thickness of the intermediate coating can influence the "self-repair" of zinc rich epoxy primer apparently,thus the changes of coating resistance in the middle stage of immersion,porosity and water absorption rate are influenced as well.