Study On Color Coating On The Aluminum Alloys By Micro-plasma Oxidation

Aluminum alloy is widely applied to engineering due to its outstanding specific strength,electrical conductivity,thermal conductivity,easily forming and making,etc. However,its lower surface hardness and poor corrosion resistance confine its appliance.So,it is important that its engineering properties are improved by surface treatment on aluminum alloy.The color coating on aluminum alloy is prepared by traditional technology, which include that film of anodic oxidation adsorb organic or inorganic color dye, and color coatings is directly formed by anode oxidation.But the coating obtained by traditional technology has labile color,lower wearing resistance and poor corrosion resistance,etc.Currently,micro-plasma oxidation is explored and developed,which is a technology that ceramic film is formed in condition of hyperthermia and heavy pressure produced by micro-plasma on aluminum alloy in given electrolyte.A film with excellent hardness,heat resistant,corrosion resistance,adhesive power and color can be prepared by said micro-plasma oxidation technology.The LD31 aluminum alloy can gain different colors of ceramic coatings in silicate aluminum electrolyte which including different additives has been studied in this paper.Microscopic analysis has been done on the micro-plasma oxidation ceramic coating.The ceramic coating is mainly composed ofα-Al₂O₃ andγ-Al₂O₃ by X ray diffraction analysis.So it can be concluded that the thickness increasing of the oxidation coating is caused primarily by means of the combination of aluminum and oxygen.After the addictives Na₂ WO₄ and NH₄ VO₃ have been added in electrolyte,W and V oxides have been found in the ceramic coating by analyzing the composition of ceramic film with the use of X-ray spectrometer.The analysis result indicate that Na₂ WO₄ and NH₄ VO₃ have been involved in the oxidation reaction and the W and V exit by means of one or more W and V oxides in the ceramic.Study and analysis found that ceramic coating showing different colors is the result of additives which involved in the oxidation reaction.The hardness and thickness have been tested,the effect of electrolyte composition and other process parameters on ceramic coating has been studied and analyzed.The friction test shows that micro-plasma oxidation ceramic film has outstanding anti-friction ability. Micro-plasma oxidation ceramic coatings with different colors have been successfully produced,and the colors of the ceramic coatings can be modified by changing electrolyte composition,process parameters and so on.Compared with traditional hard anodic oxidation coating,micro-plasma oxidation ceramic coating is superior in term of the hardness,anti-wear and colour stability.The micro-plasma oxidation ceramic color coating of LD31 aluminum alloy is studied and researched.The effect of electrolyte composition and other process parameters on ceramic coating performance such as thickness,hardness,anti-wear and so on have been systematically analyzed,and try to explain these phenomenons theoretically,the color principle of ceramic coating also has been studied.All these unknown fields need subsequent study and research.