THE EFFECT OF SEALING ON FATIGUE STRENGTH OF ANODIZED 2024-T351 ALUMINUM ALLOY USING TARTARIC-SULPHURIC ACID

• Main Author: Putu Arya Aditya Nugraha, I
• Format: Final Project
• Language: Indonesia
• Subjects: Metalurgi
• Online Access: https://digilib.itb.ac.id/gdl/view/36831
• Institution: Institut Teknologi Bandung

Tartaric-Sulphuric Acid Anodizing (TSAA) which is followed by sealing using boiling water is an environmentally friendly process that is expected to replace the process that has been containing dangerous chrome ions in the aircraft industry. That environmentally friendly process still needs to be optimized to be able to produce good corrosion resistance without neglecting the mechanical properties produced especially fatigue strength. Fatigue strength is an important aspect for the safety of aircraft structure materials. This research studied the effect of duration of sealing using boiling water on fatigue strength of Aluminum Alloys (AA) 2024- T351 that has been carried out by the TSAA process. The series of experiments begins with samples preparation consisting of racking and cleaning which includes solvent cleaning, alkaline cleaning, and acid pickling. TSAA was then carried out at anodizing potential of 14 V and temperature of 37°C. After TSAA, sealing using boiling water is done with variations in duration of 40, 50, and 60 minutes. Samples that have been carried out by the TSAA process and sealing are followed by several tests which include Salt Spray Test (SST), Eddy Current Test (ECT) and tension-tension fatigue test. SST was carried out for 96 hours to test the corrosion resistance while ECT was carried out to test the thickness of the coating. Tension-tension fatigue test was carried out at frequency of 20 Hz and load ratio of 0.1 with maximum load detail of 286, 265, 245, 225 and 204 MPa. The experiment was ended with SEM analysis to study the fracture surface of the sample that had been tested for fatigue strength and to observe the surface condition of the coating from the treatment. The test results show that the variations in duration of sealing in the range of 40-60 minutes give the same corrosion resistance. On the other hand, it is shown that the duration of sealing has a relationship that is proportional to the thickness of the coating, reduction in size and number of pores, and fatigue strength produced. The smallest coating thickness is owned by 40 minute sealing sample of 1.81 µm and the largest is owned by 60 minute sealing sample of 3.77 µm. Then the fatigue strength produced is in the High Cycle Fatigue (HCF) area or in the cycle range 104 to 105 . The SEM analysis results show that the fatigue crack is initiated from the surface of the sample which results in a ductile fracture characterized by the presence of dimples. Compared with previous study, fatigue strength produced by surface treatment in the form of Chromic Acid anodizing (CAA) followed by sealing using dichromate resulted in much higher fatigue strength than the surface treatment carried out in this study