Tribology and Corrosion Lecture Notes PDF

Tribology and Corrosion 411: CORROSION Lecturer: Dr Babatunde A. Obadele Date: 22nd OCTOBER, 2024 Corrosion LECTURE 1: WEEK 8  TEXTBOOKS/MATERIALS ❖ Tony J.A. Richardson - Shreir’s Corrosion (2009, Elsevier Science) ❖ Pierre Roberge - Handbook of Corrosion Engineering (1999,...

Tribology and Corrosion 411: CORROSION Lecturer: Dr Babatunde A. Obadele Date: 22nd OCTOBER, 2024 Corrosion LECTURE 1: WEEK 8  TEXTBOOKS/MATERIALS ❖ Tony J.A. Richardson - Shreir’s Corrosion (2009, Elsevier Science) ❖ Pierre Roberge - Handbook of Corrosion Engineering (1999, McGraw-Hill Professional) ❖ Ahmad, Z., 2006. Principles of corrosion engineering and corrosion control. Elsevier.  ASSESSMENT ❖ TEST ONE: …% ❖ TEST TWO: …% (13th of November, 2024 @ 6pm) ❖ ASSIGNMENT: …% ❖ LABORATORY: …% ❖ PRESENTATION/PROJECT:…% ❖ EXAM: 60% ❖ IT IS COMPULSORY TO SIT FOR EXAMINATION IN ORDER TO PASS THIS MODULE ❖ The Mark distribution is subject to change during the Semester.  LABORATORY ❖ LABORATORY ONE: CORROSION: GROUPS ❖ LABORATORY TWO: TRIBOLOGY ❖ CORROSION SOFTWARE: FREECORP: CORROSION PREDICTION, ANALYSIS, INTERPRETATION???? @ CMME COMPUTER LABORATORY ❖ IT IS COMPULSORY TO SIT FOR EXAMINATION IN ORDER TO PASS THIS MODULE ❖ The Mark distribution is subject to change during the Semester.  Outlines ❖ Introduction to Corrosion (Nature/Theory of Corrosion) ❖ Factors affecting Corrosion ❖ Electrochemical corrosion of metals ❖ Thermodynamics of Corrosion ❖ Galvanic cells/series ❖ Forms of Corrosion ❖ Determination of Corrosion ❖ Corrosion Testing and Monitoring ❖ Corrosion Prevention/Control ❖ Tribology-Corrosion Synergy Introduction to Corrosion (Nature/Theory of Corrosion) Materials are “attacked” by their operating environment. The degradation of metals is called Corrosion. In metals, corrosion is produced by the loss of actual material, which leaves the piece as an ion in solution, and is carried away by an electrolyte. Rust and Corrosion? Degradation: Polymers  What is Corrosion? Corrosion is the degradation of metallic materials by electrochemical means with its environment. The deterioration of materials due to reactions with their environments. ELECTRONIC COMPONENTS GALVANIC COMPONENTS PROPELLER BLADE 7 Evidences of Corrosion around us …Corrosion around us  Why do metals Corrode? 1. Metals corrode due to chemical pollution/contamination of the environment. 2. Metals are chemically unstable in the environment. Corrosion is the reverse process of metallurgy. In other words, the energy used to transform ore into a metal is reversed as the metal is exposed to oxygen and water. Corrosion Cycle of Steel  Corrosive environments Corrosion environment consists of the entire surrounding in contact with the material. Primary factors to describe the environment are: (a) Physical state – gas, liquid, or solid (b) Chemical composition – constituents and concentrations (c) Temperature (Tank storage and temperatures) For every environment – there is a particular material that is suitable for such an environment. Other factors possible – Velocity of solution (e.g: Tidal waves), Mechanical loads on materials, etc.  Corrosive environments All environments are corrosive to some degree OXIDATION AQUEOUS CORROSION High Temperature Atmosphere (rural, marine, Industrial CHEMICAL – Gases SOIL (H, O, N, etc.) (Pipelines, storage tanks) BIOLOGICAL Biofilms, human body fluids …Corrosive environment: Dental Implants  Classification of Corrosion THREE MAJOR CLASSIFICATION SYSTEM Nature of corrodent “Dry” corrosion versus “Wet” corrosion Dry corrosion or oxidation occurs when oxygen in the air reacts with metal without the presence of a liquid. Dry corrosion occurs when there is no water or moisture to aid the corrosion, and the metal oxidises with the atmosphere alone. Wet corrosion of metals occurs through electron transfer, involving two processes, oxidation and reduction. In oxidation, the metal atoms lose electrons. The surrounding environment then gains the electrons in reduction. The metal, where electrons are lost, is called the anode. The other metal, liquid or gas which gains the electrons is called the cathode. Classification of Corrosion Air contains an average of 21% oxygen, 78% nitrogen, and 1% argon. It can also contain water vapour, ozone, and carbon dioxide. Water is very commonly aerated which again means there is oxygen for reaction with metals. …Classification of Corrosion: Wet Corrosion  Classification of Corrosion Mechanism of corrosion Chemical versus Electrochemical Chemical corrosion refers to the gradual destruction of a metal's surface due to the reaction of the surface with substances in its external environment. It is often characterized by the oxidation of a metal with an acid to form oxides. Electrochemical corrosion of metals occurs when electrons from atoms at the surface of the metal are transferred to a suitable electron acceptor or depolarizer Classification of Corrosion  Classification of Corrosion Appearance of corrosion Uniform versus Localised Unlike uniform corrosion, localized corrosion occurs at discrete sites on a metal surface. Types of localized corrosion include pitting, crevice, and filiform corrosion. Uniform Localised  Corrosion Cell (The Daniell Cell) This example illustrates some of the basics of corrosion On the surface of the Zn bar, this reaction takes place: Zn → Zn +2 + 2 e − On the surface of the Cu bar, this reaction takes place Cu +2 + 2 e − → Cu Note the current path. The salt bridge provides for ion exchange. Corrosion Reaction Reduction-Oxidation (REDOX) reactions in Corrosion Reduction-Oxidation (REDOX) reactions in Corrosion Reduction-Oxidation (REDOX) reactions in Corrosion  What is needed for Corrosion 1. An anode. This is where the damage occurs. Oxidation takes place. 2. A cathode. Here’s where the reduction reaction takes place. 3. An electrolyte. (Almost any moisture will do.) 4. A current path between the cathode and anode.  Cost of Corrosion Direct cost Replacement of damaged/corroded equipment. Use of corrosion resistant alloys. Use of coatings and inhibitors. Electrochemical protection measures. Indirect cost ❑Loss of production during plant downtime. ❑Loss of product due to leakage. ❑Loss of efficiency due to corrosion (electricity, water and etc). ❑Overdesign. ❑Loss of human lives due to explosion, fire, etc. Where does corrosion happen? ATMOSPHERIC CORROSION F/A-18C Hornet Where does corrosion happen? CORROSION IN WATER Where does corrosion happen? CORROSION IN SOIL Where does corrosion happen? CORROSION IN CONCRETE  Where does corrosion happen? HIGH TEMPERATURE CORROSION  Where does corrosion happen? CHEMICAL CORROSION IN NUCLEAR REACTOR VESSEL HEAD February 16, 2002, Davis-Besse Nuclear Power Station in Oak Harbor, Ohio Boric Acid leak from control rod drive mechanism led to chemical corrosion of reactor vessel head Serious potential for loss of reactor coolant access Where does corrosion happen? ELECTRONIC COMPONENTS Where does corrosion happen? CORROSION @ BIUST Where does corrosion happen? CORROSION @ BIUST ANY QUESTION? Thank you for your attention! For more information contact: Dr B.A. OBADELE: [email protected]