Mahmoud Abbas, Rehab M. El-Maghraby, Esraa Hassan
Faculty of Petroleum and Mining Engineering, Suez University, Suez, Egypt.
Reda F. M. Elshaarawy
2Faculty of Science, Suez University, 43533 Suez, Egypt.
Improving the Corrosion Resistance of Tin-bronze by Surface Modification
Authors
Abstract
Bronze alloys are made of copper-based materials with another metal, usually tin. Many surface modification techniques such as chemical etching, oxidation, electro deposition and sol-gel could be employed to improve surface properties. The organic compound that was used in this study was extracted from chili peppers. FT-IR (Fourier-transform infrared) spectroscopy and UV (Ultraviolet) spectroscopy investigations were applied on the extracted compound and results showed that this compound is mainly capsaicin [N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-trans-6-enamide) (HMMTE)]. Electrochemical deposition was employed under cell voltage equal to 30 volts in a two-electrodes cell where bronze was the anode and stainless steel was the cathode in a solution of 10 ml/L (HMMTE)/distilled-water.
Modification of tin-bronze for 1 hr. in 10 ml/L HMMTE/ distilled water solution increased the contact angle from 48° to 132˚. Attension Biolin device (Model: Theta Optical Tensiometers) was used to measure the contact angle at ambient temperature. Electrochemical measurements revealed that a significant improvement in corrosion resistance of tin-bronze in 3.5% NaCl had been achieved. The corrosion rate of tin-bronze decreased from 10.22 mpy to 1.39 mpy. Surface morphology of the samples was investigated with scanning electron microscopy (SEN) and energy-dispersive X-ray (EDX). X-ray diffraction was employed to determined present phases. Surface investigations results confirmed that a layer of red cuprous oxide (Cu2O) was formed on the surface layer after modification which led to the improvement in corrosion resistance. Salt spray test was carried out using Alpha+ Salt Spray Testing Equipment for 13 days on the base and surface modified samples according to ASTM B117. A green layer from [CuCl2 and Cu46Cl24(OH)68-(H2O)4] was observed on the nonmodified specimen (could be patina and bronze disease) while the red layer [Cu2O] is still observed on the modified specimen. Adhesion test (using X-Cut Tape Adhesion test according to ASTM D3359) was also investigated.