Study On The Adhesion Promoter Of UV-cured Anticorrosive Coating

Due to the rapid curing speed of UV-cured coatings,shrinkage stress could not be released in time,which results in poor adhesion between coatings and metal substrates,thus limiting the application of UV-cured coatings in the field of the metal corrosion prevention.The addition of adhesion promoter is the most efficient and simplest way to improve the adhesion of UV-metal coatings.However,there were few studies on the addition of adhesion promoters to improve the adhesion between UV-cured coatings and metal substrates.The effects of different adhesion promoters on the adhesion of the UV-cured coatings,whether the same adhesion promoters could be applied to different metal substrates,and the relationship between adhesion and anti-corrosion performance of coatings remain still to be unclear.In order to solve above problems,in this paper,the influence of phosphate adhesion promoter and the silane coupling agents on the adhesion between UV-cured coatings and metal substrates(low carbon steel,aluminum plate)was systematically explored.Based on the above studies,two new biobased adhesion promoters--photosensitive phytic acid(PA-GMA),photosensitive tannic acid(TA-GMA)were synthesized successfully.The influence of biobased adhesion promoters on adhesion and anti-corrosion performance were studied.The main results were as followed.(1)The influence of phosphate ester adhesion promoter and silane coupling agent on the adhesion of UV-cured coating on metal substrates was systematically investigated by row grid method,drawing method,lap shear and wet adhesion experiment.Furthermore,the anti-corrosion performance of UV-cured metallic coatings was also determined by electrochemical impedance test and salt spray test.The results showed that the adhesion,corrosion performance of the UV-cured coating were significantly improved when adding phosphate promoters into UV-cured formulation.However,the addition of silane coupling agent had no obvious effect on the adhesion and anti-corrosion performance.It was also found that the coating with good wet adhesion tends to exhibit excellent salt spray resistance.(2)A series of photo-sensitive phytic acid(PA-GMA)with different contents of double bond was synthesized successfully via the ring opening reaction of phytic acid(PA)and glycidyl methacrylate(GMA).The structure of the PA-GMA was determined by FT-IR,~1H-NMR and the content of double bond in PA-GMA was confirmed by X-ray photoelectron spectroscopy(XPS).The effects of PA-GMA on the adhesion between coatings and metal substrates(low carbon steel plate,aluminum plate)as well as the anti-corrosion performance of coatings were systematically investigated.The results showed that PA-GMA could significantly improve the UV-cured coating adhesion.As the grafting amount increased,the adhesion promotion of PA-GMA enhanced firstly and then decreased.When the molar ratio of PA and GMA was 1:9,the efficiency of adhesion promoter PA-GMA was superior.Compared with the coating without adhesion promoter,the adhesion of the coating with PA-GMA increased from 0.44MPa(low carbon steel plate)and 0.13MPa(aluminum plate)to 2.48 MPa and 1.40 MPa,respectively.The results of electrochemical impedance test and neutral salt spray test showed that the addition of PA-GMA could enhance the anti-corrosion performance and the UV-cured coating with addition of PA-9GMA could protect the mild steel plate and aluminum plate for 500 h and 1000 h,respectively.(3)A series of photo-sensitive tannic acids(TA-GMA)with different contents of double bond were prepared via the ring opening of epoxy and hydroxyl group.The structure of TA-GMA was determined by FT-IR,~1H-NMR.The content of double bond in TA-GMA was also confirmed by ~1H-NMR.The effects of TA-GMA on the adhesion between coatings and metal substrates(low carbon steel plate,aluminum plate)as well as the anti-corrosion performance of coatings were systematically investigated.The results showed that the adhesion of UV-cured coatings was improved when TA-GMA was added,but the efficiency of TA-GMA was inferior compared with phosphate adhesion promoters.The adhesion promotion of TA-GMA enhanced firstly and decreased with the increasing grafting amount.When the molar ratio of TA and GMA was 1:20,TA-GMA exhibited the highest adhesion promoting efficiency.Compared with the coating without adhesion promoter,the adhesion was increased from 0.44MPa(low carbon steel plate)and 0.13MPa(aluminum plate)to 1.65 MPa and 1.11 MPa,respectively.The performance of metal anti-corrosion was determined by electrochemical impedance test and neutral salt spray test,the result showed the anti-corrosion of coating was improved.The UV-cured coating with TA-20GMA could protect the low carbon steel plate and aluminum plate for 500 h and 1000 h,respectively.