The Preparation And Performance Of Chemical Conversion Coating On Copper Zinc Alloys

In order to enhance the corrosion resistance and decorative of brass,metal passivation and coloring process were used to prepare chemical conversion coating on brass.The performance of the coatings were characterized by metalloscope,scanning electron microscope?SEM?,electrochemical workstation,X ray diffracmeter?XRD?,Energy Disperse Spectroscopy?EDS?,drip experiment and so on.The optimal preparation process of passivation coating and colored coating were obtained.The passivation coating of brass were prepared.Pickling effect of three acid system and hydrogen peroxide were compared.The result show three acid system which can form weak corrosion on brass surface is good for the formation of passivation coating.The effects of BTA,C₂H₅OH,conversion temperature,conversion time on the performance of the coatings were researched.The optimum formula of BTA passivation was acquired.The optimum formula is 100mg/L BTA,1ml/L C₂H₅OH,conversion temperature 60?,conversion time 90 min.Effect of different additives?rare earth salts,sodium tungstate,potassium iodide,hydrogen peroxide,OP-10 emulsifier and so on?and pH on the corrosion resistance of coating were reached.The optimum formula of BTA and CeCl₃ passivation was acquired.The optimum formula is 100 mg/L BTA,4g/L CeCl₃,1ml/L C₂H₅OH,10 g/L KI,1.5 g/L OP-10,conversion temperature 60?,conversion time 90 min.The results show that the corrosion current of BTA and CeCl₃ passivation coating is lower one unit order than the BTA passivation coating and two unit order than substrate,and the corrosion potential is higher 0.146 V than the BTA passivation coating and 0.187 V than substrate.The coating surface is dense and uniform.The main components of the coating are Ce₂O₃ and BTA-I-Cu.The purple coating of brass were prepared.The effects of Sb₂O₃,?CH₃COO?₂Cu,conversion temperature,conversion time on the performance of the coatings were researched.The optimum formula of brass purple coating was acquired.The optimum formula is 10g/L Sb₂O₃,20g/L?CH₃COO?₂Cu,conversion temperature 65?, conversion time 150 s.The curve of E-t show that the coating is formed by co-deposition of copper and zinc.The coating with good adhesion is dense and growth like petal.The corrosion current of the coating is lower one unit order than the substrate,and the corrosion potential moves 0.022 V to the forward direction.The black coating of brass were prepared.The optimum formula was acquired by orthogonal experiment.The optimum formula is 60g/L NaOH,40g/L Cu₂?OH?₂CO₃,80g/L NH₄HCO₃,conversion temperature 25?,conversion time 3min.At the same the,the optimum additional formula of colored liquid was researched.The optimum additional formula is the1:4 concentrate liquid which ammonium content reduced by10%.The pink coating of brass were prepared.The optimum formula was acquired by single factor experiment: 100 g /L CuSO₄,25 g /L NaCl,200 g /L NH₄Cl,25 g /L tartaric acid,conversion temperature 60?,conversion time 2min.The results show that The coating surface is dense and uniform.The main components of the coating is Cu₂O.The process of preparing black and pink coating of brass were used to the production of color zipper at factory.The water washing,abrasion and salt spray test result of productions can meet the requirements of actual production.This show the process can be used to industrial production.