Corrosion Failure Behavior And Service Life Prediction Of Heavy Anti-corrosion Coatings Under Saline Soil Environment

Qinghai province is the third largest saline soil distribution area in China,soluble salt in the saline soil has brought great damage to the durability of concrete,surface protective coating can protect the concrete from erosion,extend the service life of the concrete and improve the durability.According to the corrosion environment characteristics of concrete structures in saline soil area,build indoor simulation test platform,study the failure behavior of heavy anticorrosion coatings in saline soil environment.It has important practical significance on rsearch of long term heavy anti-corrosive coatings and ensure the anti-corrosion performance of concrete structures throughout entire life cycle.In this paper,the research focuses on waterborne fluorocarbon coating(FS),waterborne epoxy coating(ES),and waterborne acrylic coating(AS),indoor dry-wet cycle acceleration test,brine solution immersion test,and saline soil burial test are adopted.The changes of coatings’ morphology,conventional performance of coatings,conventional performance of concrete specimens and the resistance of the coating to chloride ion corrosion are studied,analyses the aging behavior of coated concrete from multiple perspectives,establishes the relationship between coating service life and performance index and acceleration effect of wet and dry cycles.The main conclusions are as follows:(1)The three coating systems show excellent anti-corrosion performance in the dry-wet cycle acceleration test,brine solution immersion test and saline soil burial test.In the term of protective effect on concrete is: AS>ES>FS.The main reason why the protective effect of FS coating is significantly lower than other coatings related to its microscopic defects,the excellent compactness of ES coating and AS coating after film formation makes them perform well in simulated failure tests.(2)The results of three indoor simulated failure tests show that,the failure process of heavy anti-corrosion coatings has three stages: the first stage is the failure of the top paint leading to a decrease in the gloss of the coating;the second stage is that with the failure of the top paint,when the middle paint faces the erosion of a large number of water molecules and corrosive ions,the pigment filler particles begin to lose stability and gradually peel off,causing the color of the coating to change;the third stage is that with the failure of the top paint and the intermediate paint,the primer directly faces the destruction of corrosive ions,and the adhesion between coating and substrate decreases,ultimately leading to the failure of the entire coating system.(3)According to the test data,analyze the functional relationship between glossiness,color,and adhesion with time,the results show that the service life of FS coating is 2.45 years,ES coating is 2.48 years and AS coating is 2.74 years under brine solution immersion test.Based on Fick’s second law,the service life of FS coated concrete,ES coated concrete and AS coated concrete are 21.38 years,22.32 years and 24.70 years respectively under saline soil burial test.The acceleration effects of dry and wet cycles on FS,ES and AS are 3.29,5.03 and 6.14 times compare with brine solution immersion test.