Conductive coating strategy for Magnesium alloy as a surface protection and reliability
Ooi Peng Sheng
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The methods and technologies in various coatings for magnesium alloys are studied. The magnesium alloy used in this final year project is AZ91D, which is still in very early using stages in semiconductor industry. This final year project is carried out to study on AZ91D applications and properties, especially the corrosion resistance of AZ91D. One of the most commercial solutions to prevent corrosion of AZ91D is by coated the material with a protective layer, which is called coating. Without proper coating, AZ91D is not adequate for use in harsh service conditions, as they are intrinsically highly reactive and usually have relatively poor corrosion resistance, which restricts the application of AZ91D in practical environments. Besides of corrosion resistance, coatings are also important in soldering, cosmetic, shielding, hardness and so on. There are four coating methods studied in these final year project, which are electroless nickel plating, zirconium plating, shadan passivation and spray painting. Those coatings have different function and usage, thus several testing involve surface protection and reliability properties is done to investigate, compare and determine type of coating which is the most suitable and feasible to be used. The testing involved are salt spray test, humidity test, temperature shock resistance test, dry tape adhesion test, Vickers hardness test, Norman abrasion resistance test and cross sectioning. From result obtained, spray painting have greater corrosion resistance than other coating designated for this project, but very poor reliability when subjected to sudden temperature change. Electroless nickel plating with thickest coating layer is able to provide appropriate hardness and unquestionable abrasion resistance far better than other coating sample.