BASIC MECHANISMS OF CORROSION AND （腐蚀的基本机制和）.pdfVIP

BASIC MECHANISMS OF CORROSION AND CORROSION CONTROL FOR WATER AND WASTEWATER SYSTEMS Graham E.C. Bell, Ph.D., P.E. Department Manager and Sr. VP Walking Through the Minefield of Corrosion Internal Corrosion Market Driver for Corrosion Control is Entropy Our “Business” is Guaranteed by a Fundamental Law of Nature: DS ≥ 0 universe DEFINITION OF CORROSION Corrosion is the deterioration of a substance or its properties as a result of an undesirable reaction with the environment. - NACE International It is irreversible and degenerative and related to the Second Law Thermodynamics “Energy spontaneously tends to flow only from being concentrated in one place to becoming diffused or dispersed and spread out.” Everything You Need to Know About Corrosion 4 Parts of a Corrosion Cell  Anode (location where corrosion takes place) o Oxidation Half-Reaction  Cathode (no corrosion) o Reduction Half-Reaction  Electrolyte (Soil, Water, Moisture, etc.)  Electrical Connection between anode and cathode (wire, metal wall, etc.) Electrochemical corrosion can be stopped by eliminating any one of the 4 components Electrochemical Corrosion Cell Metallic Path e- + ions A - ions C Electrolytic Path Anode Metallic Path Electron Cathode Flow