Aluminum Protection by Using Green Zirconium Oxide Layer and Organic Coating: An Efficient and Adherent Dual System

In this work, the use of ZrO2 nanocoating in aluminum substrates, generated by controlled electrochemical chronoamperometry in hexafluorozirconic acid solutions (H2ZrF6·5H2O), resulted in a lower porous films than that obtained by chemical conversion coating. After the application of an epoxy coating, long-term cyclic immersion corrosion tests and scratch tests proved the superior protection of the dual system and the coating lifespan, thanks to the enhanced adhesion of ZrO2 intermediate layer and the organic coating. As zirconium-based electrolytes are considered more friendly bath if compared to that of other conversion coating processes, like chromating, phosphating or anodizing processes, the study opens new insights to the protection of structural metals in sectors such as automotive, naval and aerospace industries. The main advantages are the employment of lightweight intermediate pre-treatment (nanoscale), compared to conventional ones (microscale), and reduction of waste slurry (electrolyte bath free of additives).

Development of a Numerical Model to Simulate Laser-Shock Paint Stripping on Aluminum Substrates

An explicit 3D Finite Element (FE) model was developed in the LS-Dyna code to simulate the laser shock paint stripping on aircraft aluminum substrates. The main objective of the model is to explain the physical mechanisms of the laser shock stripping process in terms of shock wave propagation, stress and strain evolution and stripping shape and size and to evaluate the effects of laser and material parameters on the stripping pattern. To simulate the behavior of aluminum, the Johnson–Cook plasticity model and the Gruneisen equation of state were applied. To simulate stripping, the cohesive zone modeling method was applied. The FE model was compared successfully against experiments in terms of back-face velocity profiles. The parameters considered in the study are the aluminum thickness, the epoxy paint thickness, the laser spot diameter, the fracture toughness of the aluminum/epoxy interface and the maximum applied pressure. In all cases, a circular solid or hollow stripping pattern was predicted, which agrees with the experimental findings. All parameters were found to affect the stripping pattern. The numerical results could be used for the design of selective laser shock stripping tests.

Study of making the SnO2/Sb2O3 membrane mixture on aluminum metal base as insulation and heat transfer material

SnO2 materials are attracting the attention of many scientists, because nano-sized SnO2 materials are applied to sensor, new energy, semiconductors field, etc. A typical application when coating SnO2/Sb2O3 on aluminum substrates is as a thermally conductive insulating material for electronic components such as IC cooling, microprocessors, leds, .... When changing factors such as pH solution, dipping time, calcination and calcination temperature, the structure and morphology also change, leading to changes in physico-chemical properties. The research on synthesizing nano SnO2/Sb2O3 (0.6%) by hydrothermal method brings very good results because this material has both insulating ability and high chemical and electrochemical strength, low toxicity to environment.Aluminum base is a material with mechanical strength (plasticity, malleability), high chemical resistance, good heat dissipation. When coated with SnO2/Sb2O3 on an aluminum base, this material can become a heatsink integrated board for accessories and electronic equipment (resistance value from 5÷ 15MW, thermal conductivity reaching 93.4% efficiency).

Use of Different Process Gases for Manufacturing Isolating Alumina Coatings by Flame Spraying with Cords

This study assesses the quality of flame-sprayed alumina coatings produced from recently developed alumina cord using argon and compressed air as atomizing gases. Coatings of different thicknesses were deposited on aluminum substrates and then analyzed using optical microscopy, X-ray diffraction, and resistivity measurements. The coatings, particularly those sprayed with argon, had fine microstructure and higher surface and volume resistivity than flame-spray coatings made from alumina cord in the past. They were also found to have higher alpha phase content than plasma-sprayed coatings, regardless of the atomizing gas used. The effect of humidity and the possible formation of aluminum hydroxides are also addressed.