Corrosion behavior of brass coinage in synthetic sweat solution
(1. College of Transportation Equipments and Ocean Engineering, Dalian Maritime University, Dalian 116026, China;
2. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China)
2. Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China)
Abstract: Corrosion behavior of brass coinage was investigated in synthetic sweat solution by electrochemical measurement and surface analysis methods including scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX). It is indicated that chloride ions in sweat solution accelerate the anodic active dissolution of brass, which is the main reason of pitting corrosion and dezincification corrosion. Meanwhile, lactic acid and ammonia water also promote the anode reaction. The corrosion products on the surface are mainly composed of basic copper chloride, cuprous oxide, the complex consisting of urea in association with copper, and few lactate ion. The kinetics of pitting corrosion development obeys the following equation of J0=0.3735(t+185.93)-1/2, and the process is controlled by dissolution of salt deposited on pit surface.
Key words: brass coinage; dezincification; pitting corrosion; synthetic sweat solution