STUDY THE EFFECT OF COPPER (II) NITRATE ADDITION AND TENSILE STRESS ON STRESS CORROSION CRACKING PHENOMENON OF UNS C44500 MATERIAL.

• Main Author: Adi Farrasandi, Farhan
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/56438
• Institution: Institut Teknologi Bandung

The heat exchanger tube acts as an intermediary for two or more fluids that flow both inside and outside of the heat exchanger to distribute fluid being exchanged. This process was aimed to increase efficiency level in the process industry. One of the constituent materials for the tube is UNS C44500, also known as admiralty brass. This material consists of 70Cu-30Zn, which has suitable properties for heat exchanger tubes, such as high thermal conductivity, good corrosion resistance, and good machinability, which easily formed into a component. However, admiralty brass was found susceptible to the stress corrosion cracking (SCC) phenomenon due to the nitrate compound’s activity, since the tube was also loaded by internal stress during operation. Besides, the SCC phenomenon in admiralty brass was also exacerbated by dezincification, mainly from the fluid due to previous processes, such as condensers in tap water installations dezincified caused by NaCl contamination. The effect of nitrate compounds and dezincification phenomena on SCC on C44500 Tube components will be examined by C-ring testing. The tensile stresses will be varied between 15, 45, and 85% of yield strength. The specimens were immersed into nitrate compounds consisting of NaNO3 and Cu (NO3)2 as the pH variation. Some specimens were washed using 20% HCl to give a dezincification effect. The test was carried out for five days The results obtained SCC occurred at the highest Cu(NO3)2 concentration, characterized by longitudinal crack morphology and passivity breakdown phenomena. All of the dezincified specimens were found to crack due to SCC in the immersion of 1 M Cu (NO3)2, while the undezincified specimens experienced failure when given tensile stresses in the 45% to 85% range of maximum yield strength while immersed in the same solution