Study On The Preparation And Properties Of Chrome-free Ddcromet Coating

Dacromet coating has "three high"（high corrosion resistance,high heat resistance,high permeability）and the "two advantages"（weather resistance,good adhesion properties）.It is precisely because of these excellent features so that people pay great attention to,and it has been developed and applied in many fields,such as aerospace,chemical industry,railway,automobile and so on.However,Dacromet technology has a negative side to the environment and health,because it has been used in the practical application of carcinogenic and highly toxic six valent chromium（Cr6+）.The worldwide use on chrome have very clear rules and restrictions,which is limited to the use and development of chromic acid or chromate Dacromet coating technology of passivator.With the gradual increase in people’s awareness of environmental protection,abandon the Dacromet coating in the Cr6+,the exploration and Research on environment friendly and no imminent chromium the technique of model.This paper discusses the main components of the non chromate Dacromet coating and its effect on coating and coating properties,the optimum formula of chromium free Dacromet coating liquid can completely replace chromic acid was determined by using the method of the orthogonal test,and the effects of the addition of rare earth oxide nanoparticles and the non chromium Dacromet coating corrosion resistance was used.Scanning electron microscopy（SEM）,X-ray diffraction analyses the morphology and composition of non chromium Dacromet coatings,application of polarization curves,AC impedance test（EIS）,experimental research and analysis of the brine coating corrosion resistance.The main contents and results:1.The main composition of coating liquid non chromate and each component on the corrosion resistance of the coatings is discussed,the evaluation index of orthogonal test was designed to test as a rapid corrosion resistance to NH₄NO₃,in order to determine the polyurethane used in this paper modified the optimal proportion of chrome free Dacromet of all the components.By using electrochemical techniques（polarization curve,EIS）,saline immersion experiment method to study the corrosion resistance of the coating,the best formula shows that the formula of the coating has excellent corrosion resistancewith commercially available non chromate similar.2.On the basis of chrome free Dacromet technology,selection of rare earth yttrium chloride as additives,using the method of polarization curve test,by adding rare earth yttrium chloride modified rare earth chloride non chromium Dacromet coating the best corrosion resistance when the amount of the added amount of the optimal parameters for the rare earth yttrium chloride.The optimal preparation parameters non chromate Dacromet coating and polyurethane is non chromium Dacromet coating were compared,the electrochemical impedance showed that rare earth yttrium chloride dosage 10 g/L rare earth modified chrome free Dacromet coating.The best corrosion resistance by salt immersion test and corrosion resistant ammonium nitrate rapid experimental comparison of rare earth yttrium chloride was added to 10 g/L When the performance of rare earth modified non chromium Dacromet coating and polyurethane modified non chromium Dacromet coatings,it is found that rare earth yttrium chloride chrome free Dacromet coating had better corrosion resistance than polyurethane modified non chromium Dacromet coating.3.On the basis of chrome free Dacromet technology,using SiO2 nanoparticles and Al2O3 nanoparticles as additives to SiO2 as an example,the resistance of ammonium nitrate quick corrosion experiment to determine the amount of nanoparticles prepared with the best corrosion resistance,and then adding nanoparticles optimal non chromate Dacromet coating preparation of nanoparticles SiO2 and Al2O3,with polarization curve,corrosion resistance and hardness of the electrochemical impedance comparison of two kinds of coating.The results show that the corrosion resistance of the coating of nanoparticles SiO2 and hardness were better than that of Al2O3 coating.4.By using scanning electron microscopy（SEM）,X-ray diffraction（XRD）morphology and composition analysis of the coating prepared in this paper,found that the coating is mainly composed of Zn,Al elements,in the coating is laid on the steel surface of the metal substrate and the overlapping and interlacing coating found no obvious direct matrix pores.To prevent the corrosive intrusion effectively,play a good shielding material,effectively protect the matrix and improve the coating corrosion resistance.