| Because steel is prone to corrosion in complex environment for a long time,corrosion of steel will change its structure and reduce the service life of buildings.While coating protection is an effective and economical way of protection,at present,most common coating materials are organic coatings,which often have some disadvantages such as toxicity,poor durability and poor compatibility with concrete.Geopolymers come from a wide range of sources,are economical,environmentally friendly,have simple fabrication process,and have good compatibility with concrete as well as high density and corrosion resistance.These advantages of geopolymers can be used as new directions for steel protective coatings.In this subject,metakaolin and ethylene acetate-ethylene copolymer emulsion(eva emulsion)are combined to prepare geopolymer anti-corrosion coating,which can reduce the corrosion rate of steel and the loss caused by corrosion of steel.In this paper,metakaolin-based polymer coating was prepared by alkali excitation using metakaolin-based polymer as base material and zinc oxide and aluminium hydroxide as anti-corrosion fillers.Then,the water absorption,adhesion,hardness,toughness and other properties of coated samples are tested to study the influence of different powder-liquid ratio,stirring ratio,water-binder ratio,anti-corrosion filler and coupling agent on the coating performance.The corrosion resistance of coatings with different content of anti-corrosion fillers under chloride salt immersion,dry-wet cycle and salt spray test was investigated.The mechanism was analyzed by scanning electron microscopy(SEM).Finally,the following conclusions are reached:(1)The effects of different powder-liquid ratio,stirring ratio,water-binder ratio,anti-corrosion filler and coupling agent on coating performance were studied to obtain the best coating formulation of geopolymer.With the increase of powder-liquid ratio,the water absorption and hardness of the coating gradually increase.The adhesion of the coating first increases and then decreases.The toughness of the coating gradually deteriorates.With the increase of the excitation ratio,the water absorption of the coating first decreases and then increases.The adhesion and hardness of the coating first increase and then decrease.The toughness of the coating first improves and then decreases.With the increase of the water-binder ratio,the water absorption of the coating first decreases and then increases.The adhesion of the coating first increases and then decreases.The hardness of the coating decreases gradually.The toughness of the coating improves first and then decreases.The anticorrosive filler contains zinc oxide and aluminium hydroxide,and the water absorption of the coating decreases with the increase of zinc oxide content.The adhesion and hardness of the coating first increase and then decrease.The toughness of the coating gradually improves.With the increase of aluminium hydroxide content,the water absorption gradually increases.The adhesion of the coating first increases and then decreases.The hardness of the coating decreases gradually.The toughness of the coating gradually improves.With the increase of the amount of coupling agent,the water absorption of the coating gradually decreases.The adhesion of the coating first increases and then decreases.The hardness of the coating gradually increases;The toughness of the coating gradually improves.Finally,the coating has the best comprehensive performance when the powder-liquid ratio is 1.5,the excitation ratio is 1,the water-binder ratio is 0.33,the zinc oxide content is 8%,the aluminium hydroxide content is 2%,and the coupling agent content is 3%.(2)The corrosion resistance of coatings of anticorrosive fillers with different content under the conditions of chloride salt immersion,dry-wet cycle and salt spray test was studied.In the chloride salt immersion test,wet-dry cycle test and salt spray test,the geopolymer coating with 8% zinc oxide has better corrosion resistance than that with other additions.Geopolymer coatings with 2% aluminium hydroxide have better corrosion resistance than those with other additions.The corrosion resistance of two coatings of geopolymer with8% zinc oxide content is better than that of one coat of geopolymer.In the 15-day chloride immersion test,the adhesion of coatings with 8% zinc oxide is 0.618 MPa higher than that of coatings without zinc oxide,the open-circuit potential is 0.247 V lower and the impedance modulus of coatings with 8% zinc oxide is higher than that of other polymer coatings.At the same time,combining with SEM,it can be seen that the geopolymer coating with 8% zinc oxide content is more compact and less porous than other geopolymer coatings,thus improving the corrosion resistance of the coating. |
