Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology > Metal complex layer of protection

AZ31 Magnesium Alloy Electroless Ni-P Amorphous Plating and Its Crystallization

Author WangChunMei
Tutor JingQin
School Yanshan University
Course Materials Science
Keywords AZ31 magnesium alloy Electroless nickel plating Heat treatment Hardness Corrosion resistance
CLC TG174.44
Type Master's thesis
Year 2010
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Magnesium alloy is the lightest metal in the practical application of structural materials , in addition to have high specific strength and specific stiffness , electromagnetic shielding , damping , damping , cutting , or a , in the aerospace , automotive, electronics and other areas are being increasingly wide range of applications . However , the chemical properties of magnesium alloys is very lively , and lower corrosion resistance can become constraints to further obstacle to the development of magnesium alloy . Accordingly, the magnesium alloy workpiece after a certain surface treatment step before use to provide protection . The electroless plating is one effective way of protection of the magnesium alloy workpiece , magnesium alloy after the electroless nickel plating process , and not only the corrosion resistance and abrasion resistance is improved , but also to obtain a uniform coating thickness in the complex shape of the castings . AZ31 magnesium alloy surface plating , prepared by the appearance of smooth , bright , good binding capacity Ni-P coating . Optimization of the electroless plating pre-treatment process , the main salt , a reducing agent , pH and temperature and other factors on the deposition rate . Metallographic observation , SEM observation , EDS analysis , XRD analysis , DSC analysis test method coating surface morphology , structure , composition , and crystallization transition point were measured and analyzed . Last test method by the salt spray test , polarization curves of the coating as well as coating heat treated after the performance . Magnesium alloy surface by electroless plating Ni-P treatment , its hardness has been greatly improved , nearly ten times the magnesium alloy matrix coating with excellent corrosion resistance in 3.5% NaCl solution , resulting Ni-P coating the corrosion potential relative to the matrix by nearly 800mV electroless plating samples in the salt spray chamber continuous spray 72h no peeling , flaking , magnesium alloy electroless plating corrosion resistance has been greatly improved . Electroless plating Ni-P coating the surface hardness of the coating after annealing crystallization has been greatly improved , but the corrosion resistance decreased .

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