Study On The Corrosion Mechanism Of Pure Copper In The Presence Of Ammonium Sulfate

Ammonium sulfate,widely exists in industrial atmosphere,rural atmosphere and haze,and its existence will accelerate the corrosion of copper.In this dissertation,the corrosion mechanism of Cu was investigated with the presence of ammonium sulfate.The main works of this dissertation are presented as follows:?1?The traditional potassium permanganate titration method was improved in response to that the amount of cuprous oxide,which is the most important corrosion product of copper,cannot be determined accurately before,viz.deaeration of electrolyte,dissolution of the corrosion products,specimen rinsing,oxidation of cuprous ions and titration,the high-purity nitrogen flow is bubbled throughout the whole process to maintain the oxygen-free environment except for the titration.This high accurate method with the error range of±3%can quantitatively analyze the cuprous oxide in the corrosion product regardless of uniformity of corrosion.?2?The corrosion behavior of copper in the bulky solution of ammonium sulfate.The corrosion product generated in bulky solution are main of cuprous oxide and basic copper sulfate,in which the cuprous oxide is the major phase.The layer-structrued cuprous oxide is generated on the cooper surface on the outset,The subsequently generated blue crystal is basic copper sulfate,which disperse unnifromly on cuprous oxide.It is found that the corrosion of copper was the synergistic effect of electrochemical and chemical corrosion,in which the process of copper losing one electron is an electrochemical reaction,and the free Cu²⁺reacting with the copper matrix to form Cu₂O is regarding as a chemical reaction.The chemical reaction would consume the copper matrix and promote the corrosion of copper to a great extent.In addition,the Cu?NH₃?_n²⁺is a critical intermediate for free Cu²⁺supplyment,by which the corrosion products generation on the copper surface is promoted.The dual effect of NH₄⁺is accelerating copper corrosion and hindering the formation of copper corrosion products,both of which are caused by the copper-ammonium complexation.?3?Atmospheric corrosion mechanism of copper caused by ammonium sulfate particles.The effect of particle size,deposition amount of ammonium sulfate and relative humidity of exposure atmosphere on the corrosion of copper are studied.The decrease of particle size,the increase of deposition amount and relative humidity would all promote the corrosion of copper.In addition,there are two catalytic mechanisms for the atmospheric corrosion of copper caused by ammonium sulfate particles.One is the copper-ammonium complexation effect to promote the electrochemical corrosion of copper,and the other is the mutual conversion of Cu⁺with Cu²⁺,which promotes the chemical corrosion of copper.The amount of free copper ions has a great influence on the corrosion rate of copper.