Research On Process And Corrosion Resistance Of Chromium-free Passivated Copper And Copper Alloys

Owing to its excellent electrical conductivity,thermal conductivity,cold resistance,corrosion resistance and good mechanical workability,as well as affinity with other elements,solubility and chemical stability,copper and copper alloys are a material widely used in machinery,electronics,electrical,chemical,transportation,energy,construction,information,communications and other fields.However,it must be expand their application with the development of industry technology.So,its corrosion takes placte at a significant rate at the special environment,including sea water and chloride environments.To our knowledge,nowadays,chromate passivation on the environment and human health have a great harm.Therefore,the promotion of non-chrome passivation of Cu and its alloys has strong practical significance and economic value in this work.In this paper,the chemical immersion method was used to treat different Cu materials(T2 and QCr0.5)with different passivation formulas under different passivation parameters.And then,macroscopic morphology observation,nitrate drip experiment,brine immersion experiment,X-ray diffraction analysis,X-ray photoelectron spectroscopy,' scanning electron microscopy,salt spray test,and electrochemical experiments were perfomed to investigate surface morphology,phase composition,the combination of form as well as corrosion resistance,Finally,a chromium-free passivation mechanism for copper is discussed and proposed.The following conclusions can be drawn from the present work:1.For T2 copper,the chromium-free passivation formula are composed of 4g/L TTA,4g/L BTA and 20ml/L H2O2,the passivation solution is controlled to have a pH of 4,and is passivated at 40? for 1 minute and then dried with a hair dryer for 20s.Under the aging of 24h in a natural environment,a layer of 20?m was formed on the surface of T2 copper,which mainly consisted of BTA,TTA,CuO and Cu2O,and the copper color passivation film covering the copper matrix was more dense.The corrosion current density was reduced from 8.6475·10-6A·cm-2 to 1.5660·10-6 A·cm2 than unpassivated sample,and the corrosion inhibition rate reached 81.9%.2.For QCr0.5 samples,chromium-free passivation formula consisted of 8g/L TTA,2g/L sulfosalicylic acid and 50ml/L H2O2,the passivation solution is controlled to have a pH of 6,and is passivated at 20? for 3 minute and then dried with a hair dryer for 20s.Under the aging of 24h in a natural environment,a copper color passivation film layer with a thickness of about 15 ?m is formed on the surface and consists mainly of adsorbed TTA,CuO,Cu2O,and sulfosalicylic acid copper complexes.The corrosion current density was reduced from 6.5874·10-8A·cm2 to 7.0929·10-9A·cm2 than Unpassivated sample,and the corrosion inhibition rate reached 89.23%.3.For chromium-free passivation of copper alloys,the information of the adsorption film and the oxide film were the main passivation mechanism.The main process could be divided into three steps:(1)The oxidation and dissolution of the copper matrix generates CuO and Cu2O;(2)BTA and its derivatives Adsorption of substances,BTA and TTA with Cu atoms and a copper ion to form Cu-BTA(TTA)and Cu(I)-BTA(TTA)polymer;(3)The self-stabilization of the adsorption membrane,the role of the polymer membrane in its own structure.The slower group rearrangement occurred and reached the most stable state.At the same time,CuO and Cu2O particles filled the voids of the passivation film to form a dense passivation film.