hrvatski

Korozijska stabilnost materijala u rashladnim sustavima s morskom vodom

Seawater cooling systems are usually built up from copper-nickel and copper-zinc alloys which corrosion stability is due to their continuous surface layer of corrosion products with good protection ability. During their work, in cooling systems often strong floctulations of fluid inside the tubes are damaging protective layer on copper surface leading to rapid corrosion and perforation of the tube. This work is based on investigation of jet impingement by 3.5 % NaCl on the surface corrosion of copper alloy CuNi 90/10. Applied velocitiy was from 1 to 5 ms-1. Jet impingement measurements were done after controled formation of protective layer in 3.5 % NaCl, potable water, benzotriazole solution (BTA) and FeSO4 solution in potable water. Observation of layer formation in stagnant conditions was performed on CuNi 90/10 and CuZn alloys. Layer formation was observed by measuring the polarization resistance, Tafel polarization and electrochemical impedance spectroscopy. Layers formed on CuZn alloy were analysed with scanning electron microscope (SEM-EDX). Layer degradation under jet impingement was observed by measuring the polarisation resistance. Results show that formed layers are diferent in their corrosion resistance in following this order: seawater>BTA>FeSO4>potable water. Jet impingement causes damage on the protection layer and decreases polarization resistance for 24 %, 35 %, 50 % and 92 % in case of 3.5 % NaCl, BTA, FeSO4 and potable water, respectively. Corrosion resistance of unharmed and damaged layer was compared with corrosion resistance of polished and degreased metal surface and metal surface treated with peracetic acid.

CuNi 90/10; CuZn; morska voda; erozijska korozija

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