Study On The Construction And Performance Of UV-cured Metal Anticorrosive Coatings

Metal corrosion has not only posed a threat to production and life,but also caused serious environmental pollution.At present,applying anticorrosion coatings on the surface of metal devices is the mainstream method.However,traditional solvent-based coatings have been criticized for defects such as high pollution and high energy consumption.UV-cured coatings have the advantages of high efficiency,low energy,environmental protection,etc.They are widely used in many fields,but there are few reports in the field of metal anticorrosion.There are two main reasons: First,metal anticorrosive coatings have been mainly solvent-based coatings,and there is a lack of knowledge about the factors affecting the anticorrosive performance of UV-cured metal coatings;Second,the curing rate of the UV-cured coating is too fast to release the shrinkage stress in time,and it is difficult for UV cured coatings to have strong metal adhesion.Herein,the two components of UV-cured coating: oligomer resin and reactive diluent have been studied and the influence of each component in the coating on the water absorption and anti-corrosion performance of the UV-cured coating have been systematically explored,and the influence factor of the cathodic disbondment resistance of the coating were explored.Finally,a double-layer UV-curable metal coating(primer + topcoat)was designed,and its anti-corrosion performance was evaluated.In the first part,the influence of the chemical structure of reactive diluents on the anti-corrosion properties of UV-cured coatings have been studied.A series of UV-cured metal coatings were constructed by reactive diluents with different structures and commercially available epoxy acrylate oligomers.The water absorption and anticorrosion performance of the UV cured coatings were affected by water absorption test,water contact angle test,electrochemical impedance test and neutral salt spray test.It is found that the water absorption of the UV-cured coatings was largely influenced by the chemical structure of the reactive diluent,which determined the barrier performance and anti-corrosion performance of the UV-cured coating.The reactive diluent with high functionality could increase the cross-linking density of the coating and reduce its water absorption,and the barrier performance and anti-corrosion performance of the UVcured coatings were thus improved.The alkane chain in the reactive diluent can also reduce the water absorption of the coating,but too long alkane chain leads to a decrease in the double bond content in the coating system,and decreased crosslink density of the coating,and the barrier performance and anti-corrosion performance of the UV-cured coatings were thus worsened.The benzene rings in the active diluent could improve the hydrophobicity of the UV-cured coatings,and the barrier performance and anticorrosion performance of the UV-cured coatings were improved.The water absorption and metal adhesion of UV-cured coatings increase with the increasing ether bond in the reactive diluent,and when the UV-cured coatings have low crosslink density,the adhesion of the coating is the main factor that determines the anti-corrosion performance of the UV-cured coating.The branched structure can improve the hydrophobicity of the UV-cured coating and reduce the water absorption of the coating,but too much branched structure leads to poor compatibility of coating components,which reduce the barrier performance and anti-corrosion performance of the UV-cured coatings.In the second part,the influence of the chemical structure of oligomer resin on the anti-corrosion properties of UV-cured coatings have been studied.A series of polyurethane acrylates with different soft and hard segment structures were synthesized,and used to construct UV-curable coatings.The water absorption and anti-corrosion performance of the UV cured coatings were characterized by water absorption test,water contact angle test,electrochemical impedance test and neutral salt spray test.It is found that the hydrophilicity and water absorption of the UV-cured coatings increase with the increase of the ether bond content in the soft segment,which reduce the barrier performance and anti-corrosion performance of the UV-cured coatings.The UV-cured coatings with cyclic structure(aromatic rings or aliphatic rings)of the hard segment has higher hydrophobicity,lower water absorption and stronger anti-corrosion performance than those with the linear structure of the hard segment in polyurethane acrylates;The hydrophobicity of the coatings can be improved by introducing a hydrophobic methyl group nearby the ether bond in the soft segment or reducing the density of the ether bond,both of which can reduce the water absorption of the UVcured coatings and improve the barrier performance and corrosion resistance of the coatings,but the former is more effective than the latter.In the third part,a double-layer UV curing coatings with high adhesion UV-cured primer and high barrier UV-cured top coatings were designed and constructed.First,a series of UV-cured coatings were prepared with different oligomer resins and reactive diluents,and their adhesion and anti-corrosion properties were studied.According to research findings,there is no direct relationship between the dry adhesion of the UVcured coatings and the cathodic disbondment resistance of the coatings,and the wet adhesion of the coating is the key factor affecting the cathodic disbondment resistance of the coatings.The UV-cured coatings constructed with aliphatic polyurethane acrylate and polyester acrylate has excellent dry/wet adhesion and cathodic peel resistance.It was used as a primer combining with topcoating to construct a double-layer UV-cured coating.The double-layer UV-cured coating with both excellent adhesion and barrier properties,and exhibits excellent anti-corrosion properties: for nondefect coatings,there is no blistering or rust on the coating surface after 1000 h salt spray test;for defective coatings,there is no large-scale peeling of the coating after 600 h salt spray test(corrosion product diffusion <3 mm).