| The economic and social impact of metal corrosion is so great that people have been studying the corrosion behavior and protective measures of various metals.As a common method of steel surface treatment,it is necessary to study and improve its corrosion resistance.Normal room temperature phosphating bath often contains nitrite,chlorate,nickel salt,fluoride compounds and other phosphating promoters which is harmful to the environment and human health.Therefore,it is necessary to develop a phosphating accelerator with low toxicity,low pollution and good film performance.Molybdenum disulfide can adsorb free film-forming elements and act as nucleation sites.Therefore,it can be used as a new phosphating accelerator to solve the existing problems.Based on the traditional phosphating treatment technology,Mo S2 with high specific surface area and unique three-dimensional structure was introduced in this paper to promote the production and performance of phosphating film by virtue of its excellent adsorption characteristics.In this paper,the effects of Mo S2 phosphating promoter and phosphating process on the composition,structure and corrosion resistance of phosphate coating on the surface of Q235 steel were studied.The main research work is summarized as follows:In this paper,Q235 steel plate was used as the matrix.The bulk Mo S2 powder and nano-Mo S2 particles were respectively introduced into the basic zinc phosphating formula to carry out the phosphating experiment.The orthogonal experiment was carried out to determine the optimal process parameters of nano-Mo S2 phosphating:phosphating temperature 40℃,p H2.5,phosphating time 20 min,no surface adjustment.The surface morphology and composition of the phosphate coating were characterized by field emission scanning electron microscope,energy spectrum analyzer,digital optical microscope,X-ray photoelectron spectrometer and X-ray diffractometer.The results showed that the number and size of phosphating grains increased after adding bulk Mo S2,while the structure of phosphate coating became denser and more uniform after adding nano-Mo S2 particles.The main composition of the phosphate coating does not change,which are Zn3（PO4）2·4H2O and Zn2Fe（PO4）2·4H2O.The corrosion resistance of phosphate coating was studied by electrochemical experiment and neutral salt spray experiment.The results showed that after adding 1.2 g/L nano-Mo S2 particles,the corrosion voltage of the phosphate coating increased by 0.085V,the corrosion current density decreased form 1.49ⅹ10-5μA/cm2 to 1.20ⅹ10-6μA/cm2,which decreased by an order of magnitude,and the time for the occurrence of 10%red rust in the neutral salt spray test increased from 0.2 hours to 18 hours,and the time for the occurrence of the droplet changing color increased from 2.3 seconds to 71.6 seconds. |
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