Influence of medium and temperature on the corrosion behavior and microstructure of copper and brass

U ovom je radu elektrokemijskim mjerenjima ispitana korozijska otpornost bakra i mesinga u vodovodnoj vodi i 3,5 % otopini NaCl pri sobnoj temperaturi i pri 60 °C. Promjene na površini uzoraka praćene su svjetlosnim i pretražnim elektronskim mikroskopom. Rezultati ispitivanja pokazali su da korozijska otpornost i za bakar i za mesing opada porastom temperature i u vodi i u 3,5 % otopini NaCl. Veću brzinu korozije u oba medija i pri obje ispitivane temperature pokazao je mesing, dok se bakar kao plemenitiji metal pokazao otpornijim na koroziju. Metalografskim i mikrostrukturnim ispitivanjima je ustanovljeno da se na površini bakra za vrijeme elektrokemijskog procesa u 3,5 % otopini NaCl stvara sloj bakrovog klorida, koji je nedovoljno postojan da u potpunosti spriječi prodiranje agresivnih iona iz otopine. Iz metalografskih snimaka mesinga nakon elektrokemijskih mjerenja utvrđeno je da dolazi do selektivnog otapanja cinka iz mesinga u kloridnom mediju.In this paper the corrosion resistance of copper and brass in drinking water and 3.5 % NaCl solution at room temperature and 60 °C was examined by electrochemical measurements. Changes in the surface of the samples were followed by light and scanning electron microscope. Investigation results showed that the corrosion resistance of both copper and brass decreases with temperature elevation in water and 3.5 % NaCl solution. Brass showed a higher corrosion rate in both media, while copper as a more noble metal showed more resistance to corrosion. Metallographic and microstructure investigations revealed copper chloride layer formed at copper surface during the electrochemical process in 3.5 % NaCl solution. Copper chloride layer is not stable enough to completely prevent the penetration of aggressive ions from the solution. Results of metallographic investigation of brass proved the process of dezinfication taking place at the metal surface in chloride solution