Research On Environmental-friendly Conversion Coating With Low Electrical Contact Resistant And High Corrosion Resistant On 6063 Aluminum Alloy

Aluminum alloy has good comprehensive properties,so it has a wide range of applications in navigation,aerospace,automotive,3C electronics and other fields.It is arduous yet of great significance to develop environmental friendly chemical conversion technology in terms of conductivity and corrosion resistant for improving the corrosion resistance and anti-static and electromagnetic interference（EMI）shielding performance of aluminum alloy as shielding material.It provides a strut and heat dissipation function for high-power device module,so that it has good anti electromagnetic interference,electromagnetic shielding,anti-static accumulation and other functions,which has an important role in improving the heat dissipation performance,computing efficiency,stability and data safety of electronic devices.Based on the above,three series of conversion films were prepared by adding tannic acid,potassium permanganate and Sodium vanadate into Mo/Ti-based solution separetly.The corrosion resistance and surface contact resistance（ECR）of the conversion coating were studied by a variety of characterization analysis and testing methods.The conclusions and achievements are as follows:（1）There are large cracks on the surface of the organic-metal conversion coatings（ZTV,MTT）by the surface morphology（SEM）,but no cracks for the transition metal conversion coatings（MTM,MTV）.And,it can effectively avoid the formation of micro-cracks and improve the film density by replacing tannic acid with potassium permanganate or Sodium vanadate in Mo/Ti based conversion solution.（2）The ECR of transition metal films（MTM,MTV）is smaller than those of organic metal films（ZTV,MTT）.They are 70.434 mΩ/in²,44.858 mΩ/in²,2.7992 mΩ/in² and 30.058 mΩ/in²,respectively.The ECR of MTM coating,remarkably,was decreased by even more one order of magnitude as compared with those of ZTV coating.There are harmful to the conductivity of the conversion film that micro-cracks on the surface of the conversion coating containing organic-metal complexes.（3）After the Humid-hot cycle experiment,the ECR of the samples treated by transition metal conversion was almost unchanged by the deterioration under Humid-hot environment,but the organic metal conversion film was increased nearly 2 times.These results show that the ECR of MTM and MTV conversion coating has better stability in Humid-hot environment,which could be attributed to the thermally and chemically stability of molybdate conversion film,as well as the compact and crack free transition metal conversion film.（4）As compared with the bare substrate,the drip-resistant time of the samples treated were increased by nearly 5 times.What’s more,the corrosion potential（/ V）were shifted positively by 240 m V to 490 m V,and the corrosion current density（）were decreased to 0.48 μAcm^-2 from 2.56 μAcm^-2.In addition,Mo/Ti-based conversion films were less likely to loose and fall off as compared with ZTV conversion films in the hot and humid environment.The above results show that the corrosion resistance of samples treated by Mo/Ti-based conversion solutions is greatly improved as compared with 6063 Al-alloy substrate.