Design,Synthesis And Properties Study Of An Early-stage Corrosion-detection Coating For Cu Alloys

Early-stage corrosion-detection coatings can display a sensitive,selective,nondestructive in-situ detection of metal corrosion,which is crucial for anti-corrosion system of metallic materials.Copper and its alloys are widely used in harsh conditions such as marine propeller,seawater pipeline and safety-valve,since copper possesses relative better corrosion resistance than other popular structural metal materials like steel.However,the diversity of application scenarios and corrosion environments causes significant differences in corrosion behavior of structural materials.Therefore,an efficient,accurate and rapid corrosion detection and protection methods is of great significance for maintaining equipment integrity and guaranteeing system functions.Aiming at the main issue in this field,sensitive molecular sensors to copper ions were prepared and applied to the coating of copper and its alloy materials to obtain a coating system with the function of early-stage corrosion detection for copper alloys.Since the corrosion of copper-based alloys always lead to the release of C u(II)ions,a sensor that is sensitive to Cu(II)can be employed as the corrosio n indicator for copper or copper-based alloys.In this paper we select two colo rimetric/fluorescent dual-channel selective Cu(II)sensor derived from rhodamine B hydrazide,3’,6’-Bis(diethylamino)-2-[[(2-hydroxyphenyl)methylene]amino]spiro[1H-isoindole-1,9’-[9H]xanthen]-3(2H)-one(RHS)and 3’,6’-Bis(diethylamino)-2-[[(2,4-dihydroxyphenyl)methylene]amino]spiro[1H-isoindole-1,9’-[9H]xanthen]-3(2H)-one(RHD),as the corrosion indicator.Corrosion-detection coatings were obt ained by adding RHS/RHD to the formulation of epoxy resin.Both the colori metric and fluorescent signals of the typical 0.5 wt.% RHS-doped coating was observed after 12 hours of salty spray experiment,which showed that the area prior to corrosion was no significant damage.Moreover,a zinc-based metal-organic framework(MOF),ZIF-8,was applied as the nanocontainer of corrosion indicator in this coating.The amount of RHS could be reduced in the corrosion-detection coating modified with ZIF-8,while the detection sensitivity was better than the coating with bare RHS.The signals were captured after 8 hours of salty spray experiment.In conclusion,we successfully realized early-stage corrosion detection for cupronickel in epoxy coating.which could be potentially used in the corrosion detections for copper alloys.Our method is convenient and low-cost,which could be potential for large-scale application.