EFFECT OF SHOT-PEENING AND ANODIZING VOLTAGE ON MECHANICAL PROPERTIES AND CORROSION RESISTANCE OF AZ91D MAGNESIUM ALLOYS FOR BIODEGRADABLE IMPLANT

• Main Author: Nur Rahmani, Amyra
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69102
• Institution: Institut Teknologi Bandung

Internal implant fixation has become a popular method for fracture healing due to its effectiveness and flexibility. Implant materials currently used include stainless steel, titanium alloys, and cobalt alloys. These materials cannot be degraded and absorbed by the body so surgical removal is needed when the bone has healed. Magnesium alloys have attracted researchers as biodegradable materials to eliminate the need for surgical removal of implants. However, magnesium alloys have a high corrosion rate which causes rapid degradation of mechanical properties in the physiological environment of the body. Anodizing is a surface treatment to produce a thick and stable oxide layer to protect against corrosion. Shot peening can improve mechanical properties through work hardening in magnesium alloys that are difficult to deform. a surface treatment aiming to improve alloys' mechanical properties. This study studied the effect of shot peening and anodizing voltage on the mechanical properties and corrosion resistance of AZ91D alloy in Ringer's Lactate solution. The shot peening (SP) experiment was carried out for 60 minutes. Then, anodizing was carried out on SP and without SP samples in a solution of 3 M KOH + 1 M Na2SiO3 for 60 minutes at a voltage of 5, 10, 20, and 25 V. Morphology and characterization of the composition of the anodized layer were carried out with optical microscope (OM) and scanning microscopy electron - energy dispersive spectroscopy (EDS). The hardness of SP and non-SP samples were tested using the Vickers hardness test (VHT). The surface roughness of the sample was measured using the Surface Roughness Tester (SRT). The corrosion resistance of the samples was determined by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The experiment results show that SP can increase the hardness of the sample by 50.43% to 106 HV near the surface. Anodizing at a voltage of 5 V produced a porous layer of Mg(OH)2 11.53 ?m thick. Meanwhile, at a voltage of 25 V, a 2.06 ?m thick layer of MgO was formed. SP increases the surface roughness of the anodizing layer with a maximum value of Ra equal to 15,187 ?m at an anodizing voltage of 5 V. The highest corrosion resistance was achieved when anodizing at 20 V with a corrosion rate of 0.26 mm/year and the total coating resistance and charge transfer resistance was 2626.32 ?cm2. SP decreased the corrosion resistance of anodized samples due to changes in the anodized layer and the microstructure of AZ91D alloy.