FUNDAMENTALS OF CATHODIC PROTECTION

Size: px
Start display at page:

Download "FUNDAMENTALS OF CATHODIC PROTECTION"

Transcription

1 FUNDAMENTALS OF CATHODIC PROTECTION Corrosion is the deterioration of a metal because of a reaction with its environment. For the purpose of this report, corrosion is the result of an electrochemical reaction that occurs between two different metal surfaces placed in contact with a common conductive environment. The reaction that occurs is commonly referred to as a reduction-oxidation reaction. Corrosion occurs because an electrical potential difference (voltage) exists between two sites on the metal surface in the environment. The difference may be the result of variations in the metal or in the environment. Variations in the metal may be the result of temperature, stress, metal composition or the presence of impurities. Corrosion may occur between two different sites on a single metal, or between two different types of metal placed in electrical contact with one another. Differences in the environment may be the result of variations in chemical composition, temperature, velocity and oxygen concentration. An electrolyte is a solution or substance that may conduct electrical current as an ionic charge. Water and soil are both electrolytes. The term "anode" refers to the metal surface at which corrosion occurs and from which current leaves the metal surface to enter the electrolyte. The reaction that occurs at the anode is called oxidation. The term "cathode" describes the metal surface from which current leaves the electrolyte to enter the metal. The reaction at this surface is called reduction. Typically oxygen reduction or hydrogen evolution occurs at the cathode. The term "electrolysis" refers to changes that occur in the electrolyte as a result of the corrosion process. During the corrosion process, a metal molecule leaves the metal surface and enters the electrolyte to combine with a free ion at a lower valence state. This is oxidation. Electron flow occurs in the metal between the anode and

2 cathode. Simultaneously, a reduction reaction occurs at the cathode. Electrical current flows onto the cathode surface and off of the anode surface by means of ion exchange. A corrosion cell is a circuit consisting of an anode, a cathode, an electrolyte, and an electrical contact between the anode and cathode. The diagram below represents a simple corrosion cell between a copper cathode and an iron anode placed in a beaker with electrolyte solution. CURRENT FLOW WIRE CATHODE (COPPER) ANODE (IRON) CURRENT FLOW IONIZED ELECTROLYTE CURRENT FLOW (- TO + IN ELECTROLYTE) In relation to the subject structure, the water is an electrolyte and the steel surface is the metal. Both anodic and cathodic sites exist on the steel surface due to variations in the alloy and in the water. Cathodic protection is an electrical means of mitigating corrosion on buried and submerged structures. CP involves the application of a DC (direct current) onto the surface of a metal structure. Since corrosion only occurs at locations where current discharges from a metal surface, corrosion control may be achieved by applying a net DC current flow onto the entire surface of a structure. In those areas where current collects, corrosion is controlled. Two types of cathodic protection systems exist. The first type uses galvanic anodes for protection. When metals such as magnesium or zinc are placed in the environment in contact with a more noble metal such as steel, a current flows from the more active anode to the nobler cathode. This is similar to the operation of a dry cell battery. Current flows because a potential difference

3 (voltage) exists between the two metals relative to their electrolyte. Galvanic systems are most suitable for use with low resistivity environments, well-coated structures and relatively small surface areas. No external power source is required. Galvanic systems tend to have a high initial cost with minimal maintenance costs. The diagram below depicts a galvanic anode installed on a pipeline with a test station. GALVANIC ANODE SYSTEM Test Terminal Board Test Lead Pipeline Anode The second type of system is an impressed current system. These utilize an external power source to develop a high potential difference between the surface to be protected and an anode. A series of anodes installed in the ground are referred to as a groundbed. Impressed current type systems are advantageous because high driving voltages can be developed with an external power supply. This makes it possible to achieve a much higher current output from an anode, than from an equivalent size anode on a galvanic system. Fewer anodes are required for impressed current systems than are required for a galvanic system of equal current capacity. Impressed current systems tend to have a low initial cost with higher operating and maintenance costs than a galvanic system. The following diagram depicts an impressed current system for a pipeline.

4 IMPRESSED CURRENT SYSTEM Anode Groundbed Rectifier AC Power Supply Positive Cable Negative Cable Pipeline Impressed current systems typically use a power source known as a rectifier. The rectifier converts AC power to DC power and provides adjustability to the system. The current output may be increased by increasing the voltage. A transformer is used to adjust the output voltage of the rectifier. This is accomplished by adjusting tap bars on the front panel of the unit. A rectifying element, such as a diode bridge circuit, is used to convert AC power to DC power (ripple). In place of standard diodes, silicon controlled rectifiers (SCRs) may be used in conjunction with a circuit card to maintain a specified level of protection. Automatic rectifiers with SCRs may be adjusted to maintain a set voltage, current output or structure potential. Rectifiers are commonly equipped with meters to read current and voltage outputs. Circuit breakers, lightning arrestors and fuses are used to protect the unit from power surges and faults. Shunts are calibrated resistors used to measure current flow. Filters, chokes and capacitors are sometimes used to increase efficiency and limit radio frequency (RF) interference. The anodes of both galvanic and impressed current type CP systems corrode and are eventually consumed. When conventional anode materials such as graphite and zinc corrode, the anode gets smaller and the resistance of the electrical circuit increases. By Ohm's Law (V=IR), an amount of current (I in

5 amps) will flow equal to the driving voltage (V in volts) of the circuit divided by the resistance (R in ohms) of the circuit. As the anodes corrode, the circuit resistance increases and the current output decreases. With impressed current systems, the voltage output may be adjusted in order to maintain protection. Adjustments are typically required on an annual basis. Dimensionally stable anodes, such as platinized niobium wire remain relatively consistent in size and may not require adjustment as frequently. The amount of current required to protect a structure is proportional to the surface area of bare metal being protected and environmental conditions. Coating quality influences the amount of bare metal exposed to the environment tremendously. A bare structure requires current flow onto the entire surface. A well-coated structure requires minimal current flow except at holidays (coating flaws). A well-coated tank may have a current requirement of less than 1% of an equivalent bare tank. As the coating deteriorates, the amount of current required to maintain protection increases. New systems frequently operate well below their maximum designed current output capacity, which is intended for later use in the structure's design life. If changes occur in the structural or environmental conditions, the current output and/or level of protection may be affected. Typical examples are changes in soil condition that vary the moisture content due to rain, and freezing of the ground, either around the anodes or structure. Factors which increase the soil resistivity (make it less conductive) reduce the current output; those which decrease the resistivity (make it more conductive) increase the current output. Examples of change in structural factors may be the amount of tank bottom in contact with the earth based on the fill level of a tank or changes in the electrical isolation of a pipeline system. The primary changes in a water tank system occur due to water level fluctuations. Reference cells are used to measure the level of cathodic protection being received on the structure surface. A half-cell consists of a metal rod immersed in a specific environment. The half-cell serves as a standard against which the

6 structure s potential is measured. The level of protection may be evaluated based on industry established criteria. Reference electrodes are metal rods placed in the environment for the same purpose; however, they have not been placed within a stable environment and respectively may not be as accurate. Reference cells may be permanently installed or portable. Reference cells may not function when frozen. The most popular type of reference half-cell utilized is the copper-copper sulfate (CSE) reference half-cell. It consists of a copper rod in a closed container filled with a saturated copper sulfate solution. The vessel has a porous plug that permits electrical contact when placed on the ground or in water, but does not permit the solution to be lost. A structure-to-electrolyte potential measurement is recorded by placing a reference cell in direct contact with the electrolyte (soil surface or water) and measuring the DC voltage between the reference cell and structure. If the negative meter lead is connected to the half-cell and the positive lead is connected to the structure, the proper polarity will be read. The voltmeter used should have high input impedance (2 mega-ohms minimum). The following diagram depicts the use of a reference cell. DC Volt Meter + - Half Cell Soil Pipe Potential measurements recorded with the cathodic protection current turned on include a component referred to as IR-drop. When CP current (I) flows through the environment (which has a resistance (R)) between the reference cell

7 and structure, a voltage drop occurs in the soil. Electrolyte IR-drop caused by CP always makes the structure-to-electrolyte reading appear more negative than the actual polarized potential of the structure. When the current is turned off, the current goes to zero (I=0 amps) and so does the IR-drop. IR-drop free potential measurements may be recorded immediately after turning off the CP current, but before the structure has time to depolarize. These are referred to as instant off potential measurements. They are considered more accurate than readings recorded with the current on, and are commonly used to evaluate the level of protection achieved. It is the job of the corrosion engineer to design a system which provides sufficient current, adequately distributed on the structure surface to control corrosion, while providing a reliable and safe system of suitable design life. It is the responsibility of the CP system operator to assure an adequate level of cathodic protection continues to be provided and the equipment is maintained in good working condition.

WHY METALS CORRODE By T.R.B. Watson

WHY METALS CORRODE By T.R.B. Watson WHY METALS CORRODE By T.R.B. Watson This paper will concern itself with the very basic fundamental causes of corrosion. The fact is that metals corrode through sheer cussedness. They want to corrode. This

More information

CATHODIC PROTECTION SYSTEM DESIGN

CATHODIC PROTECTION SYSTEM DESIGN CATHODIC PROTECTION SYSTEM DESIGN Presented By DENIS L ROSSI P.E. CORROSION ENGINEER New England C P Inc. Corrosion Fundamentals What is corrosion? It is defined as the degradation or deterioration of

More information

Cathodic Protection Use On Tank Bottoms & Underground Piping In Power Generation Plants

Cathodic Protection Use On Tank Bottoms & Underground Piping In Power Generation Plants Cathodic Protection Use On Tank Bottoms & Underground Piping In Power Generation Plants PG&E Office San Francisco January 18, 2007 Craig K. Meier Corrosion Control Incorporated Corrosion process for tanks

More information

CATHODIC PROTECTION SPECIFICATION

CATHODIC PROTECTION SPECIFICATION CATHODIC PROTECTION SPECIFICATION AUTOMATICALLY CONTROLLED IMPRESSED CURRENT CATHODIC PROTECTION SYSTEM FOR THE INTERIOR OF STEEL WATER TANKS A. SCOPE The cathodic protection design/install constructor

More information

TROUBLESHOOTING PRELIMINARY

TROUBLESHOOTING PRELIMINARY TROUBLESHOOTING PRELIMINARY To troubleshoot, one must first have a working knowledge of the individual parts and their relation to one another. Must have adequate hand tools Must have basic instrumentation:

More information

Corrosion and Cathodic Protection Theory

Corrosion and Cathodic Protection Theory Corrosion and Cathodic Protection Theory by James B. Bushman, P.E. Principal Corrosion Engineer Bushman & Associates, Inc Medina, Ohio USA The contents of this white paper including all graphics are protected

More information

HOW TO PREDICT WHETHER A REDOX REACTION WILL BE SPONTANEOUS:

HOW TO PREDICT WHETHER A REDOX REACTION WILL BE SPONTANEOUS: Chemistry 12 UNIT 5 OXIDATION AND REDUCTION PACKAGE #2 HOW TO PREDICT WHETHER A REDOX REACTION WILL BE SPONTANEOUS: Looking at the table in the data booklet on page 8, INCREASING TENDENCY TO REDUCE = INCREASING

More information

reduction ore = metal oxides metal oxidation

reduction ore = metal oxides metal oxidation Cathodic Protection and Interferences René Gregoor Madrid, June 18 th and 19 th 2009 1 Cathodic protection and interferences Corrosion Cathodic protection Protection criterion ON potential measurements

More information

Understanding and Preventing Guyed Tower Failure Due to Anchor Shaft Corrosion

Understanding and Preventing Guyed Tower Failure Due to Anchor Shaft Corrosion Understanding and Preventing Guyed Tower Failure Due to Anchor Shaft Corrosion Craig M. Snyder, President Sioux Falls Tower Specialists, Inc./ AnchorGuard - Corrosion Control For Tower Anchors Sioux Falls,

More information

o Electrons are written in half reactions but not in net ionic equations. Why? Well, let s see.

o Electrons are written in half reactions but not in net ionic equations. Why? Well, let s see. REDOX REACTION EQUATIONS AND APPLICATIONS Overview of Redox Reactions: o Change in Oxidation State: Loses Electrons = Oxidized (Oxidation number increases) Gains Electrons = Reduced (Oxidation Number Reduced)

More information

ELECTROCHEMICAL CELLS

ELECTROCHEMICAL CELLS 1 ELECTROCHEMICAL CELLS Allessandra Volta (1745-1827) invented the electric cell in 1800 A single cell is also called a voltaic cell, galvanic cell or electrochemical cell. Volta joined several cells together

More information

Model RI ICE Pack Impressed Current Electronic Package the remedy for Mag headaches Typical Applications:

Model RI ICE Pack Impressed Current Electronic Package the remedy for Mag headaches Typical Applications: Model RI ICE Pack Impressed Current Electronic Package the remedy for Mag headaches Typical Applications: Replaces Mg anodes for cathodic protection of underground structures Useful for spot protection

More information

Corrosion Control & Cathodic Protection for Water & Wastewater Systems

Corrosion Control & Cathodic Protection for Water & Wastewater Systems Corrosion Control & Cathodic Protection for Water & Wastewater Systems Presented By: James T Lary Corrpro Companies, Inc 1090 Enterprise Dr. Medina, OH 44256 Tel. 330-723 723-5082 (x1215) email: jlary@corrpro.com

More information

The Electrical Control of Chemical Reactions E3-1

The Electrical Control of Chemical Reactions E3-1 Experiment 3 The Electrical Control of Chemical Reactions E3-1 E3-2 The Task In this experiment you will explore the processes of oxidation and reduction, in which electrons flow between materials, and

More information

5. The overall reaction in a electrochemical cell is. Zn(s) + Cu 2+ (aq) Zn 2+ (aq) + Cu(s).

5. The overall reaction in a electrochemical cell is. Zn(s) + Cu 2+ (aq) Zn 2+ (aq) + Cu(s). 1. Which process occurs in an operating voltaic cell? A) Electrical energy is converted to chemical energy. B) Chemical energy is converted to electrical energy. C) Oxidation takes place at the cathode.

More information

Galvanic Cells. SCH4U7 Ms. Lorenowicz. Tuesday, December 6, 2011

Galvanic Cells. SCH4U7 Ms. Lorenowicz. Tuesday, December 6, 2011 Galvanic Cells SCH4U7 Ms. Lorenowicz 1 Electrochemistry Concepts 1.Redox reactions involve the transfer of electrons from one reactant to another 2.Electric current is a flow of electrons in a circuit

More information

Testing Cathodic-Protection Systems

Testing Cathodic-Protection Systems Testing Cathodic-Protection Systems by Marcel Moreau Testing cathodically protected structures is rarely a cookbook type of procedure. A clear understanding of cathodic-protection principles is a prerequisite

More information

Part A Corrosion of metals

Part A Corrosion of metals Part A Corrosion of metals This section on the corrosion of metals is greatly simplified for purposes of clarity. It is not meant to train the student with the intention of making him/her an expert in

More information

Article 510 CORROSION PROTECTION Adopted by the CGA Board of Directors on October 14, 2006

Article 510 CORROSION PROTECTION Adopted by the CGA Board of Directors on October 14, 2006 California Groundwater Association An NGWA Affiliate State PO Box 14369 * Santa Rosa * CA 95402 707-578-4408; FAX: 707-546-4906; email: wellguy@groundh2o.org Article 510 CORROSION PROTECTION Adopted by

More information

Electrochemical cells

Electrochemical cells Electrochemical cells Introduction: Sudha Madhugiri D.Chem. Collin College Department of Chemistry Have you used a battery before for some purpose? I bet you have. The type of chemistry that is used in

More information

Standard Test Method Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems

Standard Test Method Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems NACE Standard TM0497-2012 Item No. 21231 Standard Test Method Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Piping Systems This NACE Standard is

More information

Electrochemistry. I. Applications of Oxidation/Reduction Reactions. Chapter 10. B. Terminology. A. History. B. Examples

Electrochemistry. I. Applications of Oxidation/Reduction Reactions. Chapter 10. B. Terminology. A. History. B. Examples Electrochemistry Chapter 10 Joesten If a molecule is oxidized it loses H and changes the oxygen bond by either increasing the number of oxygens or by sharing more electrons. If it gains hydrogen it is

More information

INTRODUCTION: The following paper is intended to inform on the subject at hand and is based on years of laboratory observations.

INTRODUCTION: The following paper is intended to inform on the subject at hand and is based on years of laboratory observations. INTRODUCTION: The following paper is intended to inform on the subject at hand and is based on years of laboratory observations. What does Galvanic Corrosion mean regarding my connector system/contact

More information

GUIDELINES FOR THE EVALUATION OF UNDERGROUND STORAGE TANK CATHODIC PROTECTION SYSTEMS

GUIDELINES FOR THE EVALUATION OF UNDERGROUND STORAGE TANK CATHODIC PROTECTION SYSTEMS GUIDELINES FOR THE EVALUATION OF UNDERGROUND STORAGE TANK CATHODIC PROTECTION SYSTEMS DEPARTMENT OF NATURAL RESOURCES UNDERGROUND STORAGE TANK MANAGEMENT PROGRAM 4244 INTERNATIONAL PARKWAY, SUITE 104 ATLANTA,

More information

Oil and Gas Pipeline Design, Maintenance and Repair

Oil and Gas Pipeline Design, Maintenance and Repair Oil and Gas Pipeline Design, Maintenance and Repair Dr. Abdel-Alim Hashem Professor of Petroleum Engineering Mining, Petroleum & Metallurgical Eng. Dept. Faculty of Engineering Cairo University aelsayed@mail.eng.cu.edu.eg

More information

GALVANIC CATHODIC PROTECTION 1.0 CONTENTS. 1.1 Aluminium Anodes. 1.2 Zinc Anodes. 1.3 Magnesium Anodes SECTION

GALVANIC CATHODIC PROTECTION 1.0 CONTENTS. 1.1 Aluminium Anodes. 1.2 Zinc Anodes. 1.3 Magnesium Anodes SECTION SECTION 1 GALVANIC CATHODIC PROTECTION 1.0 CONTENTS 1.1 Aluminium Anodes 1.1.1 Aluminium Tank Anodes 1.1.2 Aluminium Hull Anodes 1.1.3 Aluminium Platform / Jetty Anodes 1.2 Zinc Anodes 1.2.1 Zinc Tank

More information

Chapter 13: Electrochemistry. Electrochemistry. The study of the interchange of chemical and electrical energy.

Chapter 13: Electrochemistry. Electrochemistry. The study of the interchange of chemical and electrical energy. Chapter 13: Electrochemistry Redox Reactions Galvanic Cells Cell Potentials Cell Potentials and Equilbrium Batteries Electrolysis Electrolysis and Stoichiometry Corrosion Prevention Electrochemistry The

More information

Discovering Electrochemical Cells

Discovering Electrochemical Cells Discovering Electrochemical Cells Part I Electrolytic Cells Many important industrial processes PGCC CHM 102 Cell Construction e e power conductive medium What chemical species would be present in a vessel

More information

Redox and Electrochemistry

Redox and Electrochemistry Redox and Electrochemistry Oxidation: Historically means the combination of a substance with oxygen 2Mg + O 2 2MgO Oxygen is called the oxidizing agent, and magnesium is the substance oxidized. Reduction:

More information

Analog DCVG Holiday Detector

Analog DCVG Holiday Detector Analog DCVG Holiday Detector Model EPT- 4000 Survey Instrument Electronic Pipeline Technology 26 Palomino Drive, Richmond Hill, Ontario, Canada, L4C 0P8 Tel: (905) 918-0025 Fax: (905) 918-0033 www.ep-tech.ca

More information

Chemistry of Voltaic Cells

Chemistry of Voltaic Cells Chemistry of Voltaic Cells An electrochemical cell consists of two parts, called half-cells, in which the separate oxidation and reduction reactions take place. Each half cell contains a metal electrode

More information

EXPERIMENT 10 Electrochemical Cells

EXPERIMENT 10 Electrochemical Cells EXPERIMENT 10 Electrochemical Cells Introduction An electrochemical cell is a device that may be used for converting chemical energy into electrical energy. An oxidationreduction reaction is the basis

More information

Electrochemistry and Concentration Effects on Electrode Potentials

Electrochemistry and Concentration Effects on Electrode Potentials Electrochemistry and Concentration Effects on Electrode Potentials Special mention and thanks goes to Dr. Timothy Friebe for his help in developing this laboratory write-up. Introduction You have already

More information

Guidance Notes. Installation & Inspection of Fuel Cells May What is a fuel cell? Page 1

Guidance Notes. Installation & Inspection of Fuel Cells May What is a fuel cell? Page 1 Guidance Notes Installation & Inspection of Fuel Cells May 2011 This document has been prepared by Energy Safe Victoria to provide guidance for electrical contractors and licensed electrical inspectors

More information

Experiment 12: Building a Conductivity Detector and Testing for Ions. Experiment 22: Chemical Reactions and Electricity

Experiment 12: Building a Conductivity Detector and Testing for Ions. Experiment 22: Chemical Reactions and Electricity Experiment 12: Building a Conductivity Detector and Testing for Ions and Experiment 22: Chemical Reactions and Electricity What are these labs about? Prelab Lecture The common thread of these two labs

More information

Underground Storage Tanks

Underground Storage Tanks Underground Storage Tanks An Informational and Guidance Document for the University Community. Please contact Yale Environmental Health and Safety for latest Regulatory Requirements. A typical UST installation

More information

Determining What Factors Affect the Rate of Electroplating

Determining What Factors Affect the Rate of Electroplating Determining What Factors Affect the Design Research Question Variables Hypothesis Materials How does adjusting the current flowing through an electrolytic cell influence the rate at which a metal is electroplated?

More information

Maxwell Technologies GmbH Brucker Strasse 21 D Gilching Germany Phone: +49 (0) Fax: +49 (0)

Maxwell Technologies GmbH Brucker Strasse 21 D Gilching Germany Phone: +49 (0) Fax: +49 (0) WHITE PAPER DESIGN CONSIDERATIONS FOR ULTRACAPACITORS Maxwell s BOOSTCAP ultracapacitors are increasingly being utilized in consumer electronics, traction, automotive, telecoms and industrial, with applications

More information

CATHODIC PROTECTION P E FRANCIS

CATHODIC PROTECTION P E FRANCIS CATHODIC PROTECTION P E FRANCIS CONTENTS 1 INTRODUCTION...2 2 PRINCIPLES OF CATHODIC PROTECTION...3 3 METHODS OF APPLYING CATHODIC PROTECTION...5 3.1 IMPRESSED CURRENT...5 3.2 SACRIFICIAL ANODES...6 4

More information

Experiment 12: Building a Conductivity Detector and Testing for Ions. Experiment 22: Chemical Reactions and Electricity

Experiment 12: Building a Conductivity Detector and Testing for Ions. Experiment 22: Chemical Reactions and Electricity Experiment 12: Building a Conductivity Detector and Testing for Ions and Experiment 22: Chemical Reactions and Electricity What are these labs about? Prelab Lecture Samuel A. Abrash The common thread of

More information

Solving Corrosion Problems On Cast Iron & Ductile Iron Water Mains

Solving Corrosion Problems On Cast Iron & Ductile Iron Water Mains Solving Corrosion Problems On Cast Iron & Ductile Iron Water Mains Presented by: ADITYA SHANKAR GAURAV Regd. No.: 0501223221 Roll No.: ML-21 Dept. Of Mechanical Engg. Krupajal Engineering College Under

More information

E23 OXIDATION AND REDUCTION Electron Transfer Reactions

E23 OXIDATION AND REDUCTION Electron Transfer Reactions E23 OXIDATION AND REDUCTION Electron Transfer Reactions Electron Transfer There are many reactions that involve electron transfers. For example, the reaction between Fe 3+ and H 2 S below involves the

More information

Experiment 12: Building a Conductivity Detector and Testing for Ions. Experiment 22: Chemical Reactions and Electricity

Experiment 12: Building a Conductivity Detector and Testing for Ions. Experiment 22: Chemical Reactions and Electricity Experiment 12: Building a Conductivity Detector and Testing for Ions and Experiment 22: Chemical Reactions and Electricity What are these labs about? Prelab Lecture Samuel A. Abrash The common thread of

More information

Chapter 18. Oxidation Reduction Reactions and Electrochemistry

Chapter 18. Oxidation Reduction Reactions and Electrochemistry Chapter 18 Oxidation Reduction Reactions and Electrochemistry Chapter 18 Table of Contents 18.1 Oxidation Reduction Reactions 18.2 Oxidation States 18.3 Oxidation Reduction Reactions Between Nonmetals

More information

Mixed Potentials Concepts and Basics

Mixed Potentials Concepts and Basics Lecture 11 Mixed Potentials Concepts and Basics Keywords: Mixed Potential, Charge Conservation, Corrosion Potential Principle of charge conservation: Total rate of oxidation must be equal to total rate

More information

EXPERIMENT #9 CORROSION OF METALS

EXPERIMENT #9 CORROSION OF METALS EXPERIMENT #9 CORROSION OF METALS Objective The objective of this experiment is to measure the corrosion rate of two different metals and to show the effectiveness of the use of inhibitors to protect metals

More information

Topics Covered in Chapter 12

Topics Covered in Chapter 12 Chapter 12 Batteries Topics Covered in Chapter 12 12-1: Introduction to Batteries 12-2: The Voltaic Cell 12-3: Common Types of Primary Cells 12-4: Lead-Acid Wet Cell 12-5: Additional Types of Secondary

More information

The full wave rectifier consists of two diodes and a resister as shown in Figure

The full wave rectifier consists of two diodes and a resister as shown in Figure The Full-Wave Rectifier The full wave rectifier consists of two diodes and a resister as shown in Figure The transformer has a centre-tapped secondary winding. This secondary winding has a lead attached

More information

Electrochemical Half Cells and Reactions

Electrochemical Half Cells and Reactions Suggested reading: Chang text pages 81 89 Cautions Heavy metals, such as lead, and solutions of heavy metals may be toxic and an irritant. Purpose To determine the cell potential (E cell ) for various

More information

Electrochemistry Voltaic Cells

Electrochemistry Voltaic Cells Electrochemistry Voltaic Cells Many chemical reactions can be classified as oxidation-reduction or redox reactions. In these reactions one species loses electrons or is oxidized while another species gains

More information

Chapter 21a Electrochemistry: The Electrolytic Cell

Chapter 21a Electrochemistry: The Electrolytic Cell Electrochemistry Chapter 21a Electrochemistry: The Electrolytic Cell Electrochemical reactions are oxidation-reduction reactions. The two parts of the reaction are physically separated. The oxidation reaction

More information

To determine relative oxidizing and reducing strengths of a series of metals and ions.

To determine relative oxidizing and reducing strengths of a series of metals and ions. Redox Reactions PURPOSE To determine relative oxidizing and reducing strengths of a series of metals and ions. GOALS 1 To explore the relative oxidizing and reducing strengths of different metals. 2 To

More information

An explanation of the phenomenon for non-corrosion and non-electrical specialists. Written by Richard Lindley and Ken Lax and presented by Ken Lax of

An explanation of the phenomenon for non-corrosion and non-electrical specialists. Written by Richard Lindley and Ken Lax and presented by Ken Lax of An explanation of the phenomenon for non-corrosion and non-electrical specialists. Written by Richard Lindley and Ken Lax and presented by Ken Lax of Asset Integrity Services Ltd FIRSTLY WE ARE GOING TO

More information

Name Electrochemical Cells Practice Exam Date:

Name Electrochemical Cells Practice Exam Date: Name Electrochemical Cells Practice Exam Date: 1. Which energy change occurs in an operating voltaic cell? 1) chemical to electrical 2) electrical to chemical 3) chemical to nuclear 4) nuclear to chemical

More information

Power Supplies. 1.0 Power Supply Basics. www.learnabout-electronics.org. Module

Power Supplies. 1.0 Power Supply Basics. www.learnabout-electronics.org. Module Module 1 www.learnabout-electronics.org Power Supplies 1.0 Power Supply Basics What you ll learn in Module 1 Section 1.0 Power Supply Basics. Basic functions of a power supply. Safety aspects of working

More information

Electrochemistry: study of the relationship between chemical change and electrical energy

Electrochemistry: study of the relationship between chemical change and electrical energy Electrochemistry Electrochemistry Chapter 20 Electrochemistry Electrochemistry: study of the relationship between chemical change and electrical energy Investigated through use of electrochemical cells:

More information

Conductivity of Electrolytes in Solution

Conductivity of Electrolytes in Solution Conductivity of Electrolytes in Solution Introduction: Electrical current can be thought of as the movement of electrons or ionic charges from an area of high potential to an area of low potential. Materials

More information

ELECTRICAL TRAINING 7 DAYS D.C. 1.0 Electron Theory, Voltaic Cells. And Electromagnetism. Materials 3.0 Resistances In Series And Parallel.

ELECTRICAL TRAINING 7 DAYS D.C. 1.0 Electron Theory, Voltaic Cells. And Electromagnetism. Materials 3.0 Resistances In Series And Parallel. Num TITLE TABLE OF CONTENT OBJECTIVES DURATION UNIT E-01 FUNDAMENTALS OF 1.0 Electron Theory, Voltaic Cells Describe The Atomic D.C. And Electromagnetism. Structure And Its Influence 2.0 D.C. Circuits

More information

Electrochemistry - ANSWERS

Electrochemistry - ANSWERS Electrochemistry - ANSWERS 1. Using a table of standard electrode potentials, predict if the following reactions will occur spontaneously as written. a) Al 3+ + Ni Ni 2+ + Al Al 3+ + 3e - Al E = -1.68

More information

A Review of the Construction of Electrochemical Cells

A Review of the Construction of Electrochemical Cells CHEM331 Physical Chemistry Revision 2.0 A Review of the Construction of Electrochemical Cells Electrochemical cells provide us with our first real example of a system which performs non-pv work. The work

More information

Redox and Electrochemistry

Redox and Electrochemistry Name: Thursday, May 08, 2008 Redox and Electrochemistry 1. A diagram of a chemical cell and an equation are shown below. When the switch is closed, electrons will flow from 1. the Pb(s) to the Cu(s) 2+

More information

Practical Examples of Galvanic Cells

Practical Examples of Galvanic Cells 56 Practical Examples of Galvanic Cells There are many practical examples of galvanic cells in use in our everyday lives. We are familiar with batteries of all types. One of the most common is the lead-acid

More information

Line Reactors and AC Drives

Line Reactors and AC Drives Line Reactors and AC Drives Rockwell Automation Mequon Wisconsin Quite often, line and load reactors are installed on AC drives without a solid understanding of why or what the positive and negative consequences

More information

ELECTROCHEMICAL CELLS LAB

ELECTROCHEMICAL CELLS LAB ELECTROCHEMICAL CELLS LAB Purpose: The purpose of this lab is to demonstrate the ability of chemistry to make electric current using oxidation/reduction (REDOX) reactions, and to measure the electric current

More information

A simple illustration of the various forms of corrosion is shown in below Figure

A simple illustration of the various forms of corrosion is shown in below Figure CORROSION FORM we have mainly (more or less implicitly) assumed that: 1) electrochemical corrosion is the only deterioration mechanism; ) anodic and cathodic reactions take place all over the electrode

More information

Chapter 17 Study Questions Name: Class:

Chapter 17 Study Questions Name: Class: Chapter 17 Study Questions Name: Class: Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 1. If two charges repel each other, the two charges

More information

Galvanic cell and Nernst equation

Galvanic cell and Nernst equation Galvanic cell and Nernst equation Galvanic cell Some times called Voltaic cell Spontaneous reaction redox reaction is used to provide a voltage and an electron flow through some electrical circuit When

More information

Power to Go SCIENCE TOPICS PROCESS SKILLS VOCABULARY

Power to Go SCIENCE TOPICS PROCESS SKILLS VOCABULARY SIDE DISPLAY Power to Go Visitors observe an electrochemical cell constructed from a small jar containing zinc and copper strips immersed in separate solutions. The strips are connected to a motor that

More information

Determining Equivalent Weight by Copper Electrolysis

Determining Equivalent Weight by Copper Electrolysis Purpose To determine the equivalent mass of copper based on change in the mass of a copper electrode and the volume of hydrogen gas generated during an electrolysis experiment. The volume of hydrogen gas

More information

Building Electrochemical Cells

Building Electrochemical Cells Cautions Heavy metals, such as lead, and solutions of heavy metals may be toxic and an irritant. Purpose To determine the cell potential (E cell ) for various voltaic cells and compare the data with the

More information

DC MEASUREMENTS IN STRAY VOLTAGE INVESTIGATIONS

DC MEASUREMENTS IN STRAY VOLTAGE INVESTIGATIONS DC MEASUREMENTS IN STRAY VOLTAGE INVESTIGATIONS Michael F. Stringfellow, Ph.D., P.E. The Infamous Bucket Test Currents measured through water bucket as cows drink Currents present when AC power cut to

More information

5.111 Principles of Chemical Science

5.111 Principles of Chemical Science MIT OpenCourseWare http://ocw.mit.edu 5.111 Principles of Chemical Science Fall 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 25.1 5.111 Lecture

More information

Type SA-1 Generator Differential Relay

Type SA-1 Generator Differential Relay ABB Automation Inc. Substation Automation and Protection Division Coral Springs, FL 33065 Instruction Leaflet 41-348.11C Effective: November 1999 Supersedes I.L. 41-348.11B, Dated August 1986 ( ) Denotes

More information

ELECTROLYSIS. Explain why molten ionic compounds conduct electricity but solid ionic compounds do not.

ELECTROLYSIS. Explain why molten ionic compounds conduct electricity but solid ionic compounds do not. G10 worksheet for Electrloysis ELECTROLYSIS By the end of the topic, students should be able to: Explain why molten ionic compounds conduct electricity but solid ionic compounds do not. State in which

More information

How Sensors Work. How Oxygen, Electrochemical Toxic, and Metal Oxide Semiconductor Sensors Work *

How Sensors Work. How Oxygen, Electrochemical Toxic, and Metal Oxide Semiconductor Sensors Work * How Oxygen, Electrochemical Toxic, and Metal Oxide Semiconductor Sensors Work * 1. Oxygen sensor detection principle Most portable or survey instruments used for workplace evaluation of oxygen concentrations

More information

CHAPTER 17 NOTES FOR EIGHTH GRADE PHYSICAL SCIENCE ALL MATTER IS COMPOSED OF VERY SMALL PARTICLES CALLED ATOMS.

CHAPTER 17 NOTES FOR EIGHTH GRADE PHYSICAL SCIENCE ALL MATTER IS COMPOSED OF VERY SMALL PARTICLES CALLED ATOMS. CHAPTER 17 NOTES FOR EIGHTH GRADE PHYSICAL SCIENCE ALL MATTER IS COMPOSED OF VERY SMALL PARTICLES CALLED ATOMS. THE LAW OF ELECTRIC CHARGES STAES THAT LIKE CHARGES REPEL AND OPPOSITE CHARGES ATTRACT. BECAUSE

More information

CATHODIC PROTECTION MODELLING OF BURIED STRUCTURES

CATHODIC PROTECTION MODELLING OF BURIED STRUCTURES CATHODIC PROTECTION MODELLING OF BURIED STRUCTURES By ALOK SHANKAR A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER

More information

DETERMINATION OF EQUILIBRIUM CONSTANTS

DETERMINATION OF EQUILIBRIUM CONSTANTS DETERMINATION OF EQUILIBRIUM CONSTANTS USING GALVANIC CELLS PURPOSE The purpose of this experiment is to prepare several electrochemical cells and compare the relative voltages of the half-cells. This

More information

SAMPLE. Cells and Batteries. Learner Workbook. Version 1. Product Code: Training and Education Support Industry Skills Unit Meadowbank

SAMPLE. Cells and Batteries. Learner Workbook. Version 1. Product Code: Training and Education Support Industry Skills Unit Meadowbank Learner Workbook Version 1 Training and Education Support Industry Skills Unit Meadowbank Product Code: 5641 Table of contents Introduction... 5 Section 1: Primary cells... 7 Review questions... 15 Section

More information

Electrolytic Electromigration of Metallic Material and Silver Filled Epoxy

Electrolytic Electromigration of Metallic Material and Silver Filled Epoxy Electrolytic Electromigration of Metallic Material and Silver Filled Epoxy Electrolytic Electromigration Basics The most common electrolytic electromigration process in modern electronics is that associated

More information

Figure 1. A voltaic cell Cu,Cu 2+ Ag +, Ag. gas is, by convention, assigned a reduction potential of 0.00 V.

Figure 1. A voltaic cell Cu,Cu 2+ Ag +, Ag. gas is, by convention, assigned a reduction potential of 0.00 V. Voltaic Cells Introduction In this lab you will first prepare a set of simple standard half-cells and then measure the voltage between the half-cells with a voltmeter. From this data you will be able to

More information

WIRELESS REMOTE MONITORING OF CATHODIC PROTECTION SYSTEMS. John Hawkyard MICorr Deputy General Manager Rawabi Corrosion Technology Co Ltd Al-Khobar

WIRELESS REMOTE MONITORING OF CATHODIC PROTECTION SYSTEMS. John Hawkyard MICorr Deputy General Manager Rawabi Corrosion Technology Co Ltd Al-Khobar WIRELESS REMOTE MONITORING OF CATHODIC PROTECTION SYSTEMS John Hawkyard MICorr Deputy General Manager Rawabi Corrosion Technology Co Ltd Al-Khobar INTRODUCTION Cathodic Protection is an electrochemical

More information

Battery Handbook. By: RON SMITH

Battery Handbook. By: RON SMITH Battery Handbook By: RON SMITH Information compiled from the Battery Charger Handbook and the Battery Handbook written by Alvin G. Graham, Chief Engineer, Ratelco Electronics Inc. Introduction The purpose

More information

AC Direct Off-Line Power Supplies

AC Direct Off-Line Power Supplies AC Direct Off-Line Power Supplies r Introduction Many DC power supplies found in electronic systems, including those in this Tech School, rectify the 120 volts available at an electric outlet. The initial

More information

ANADOLU UNIVERSITY DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

ANADOLU UNIVERSITY DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING ANADOLU UNIVERSITY DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING EEM 102 INTRODUCTION TO ELECTRICAL ENGINEERING EXPERIMENT 9: DIODES AND DC POWER SUPPLY OBJECTIVE: To observe how a diode functions

More information

M A S S A C H U S E T T S I N S T I T U T E O F T E C H N O L O G Y. 3.014 Materials Laboratory Fall 2006

M A S S A C H U S E T T S I N S T I T U T E O F T E C H N O L O G Y. 3.014 Materials Laboratory Fall 2006 D E P A R T M E N T O F M A T E R I A L S S C I E N C E A N D E N G I N E E R I N G M A S S A C H U S E T T S I N S T I T U T E O F T E C H N O L O G Y 3.014 Materials Laboratory Fall 2006 LABORATORY 3:

More information

www.klmtechgroup.com TABLE OF CONTENT

www.klmtechgroup.com TABLE OF CONTENT Page : 1 of 13 Project Engineering Standard www.klmtechgroup.com KLM Technology #03-12 Block Aronia, Jalan Sri Perkasa 2 Taman Tampoi Utama 81200 Johor Bahru Malaysia ELECTIRAL GROUNDING TABLE OF CONTENT

More information

Module 5 : Electrochemistry Lecture 22 : Free energy and EMF

Module 5 : Electrochemistry Lecture 22 : Free energy and EMF Module 5 : Electrochemistry Lecture 22 : Free energy and EMF Objectives After studying this Lecture you will be able to Distinguish between electrolytic cells and galvanic cells. Write the cell representation

More information

Magnesium TM. Soil Anodes. High Potential Magnesium. Production - Quality Control. Laboratory- Testing. Packaging- Availability

Magnesium TM. Soil Anodes. High Potential Magnesium. Production - Quality Control. Laboratory- Testing. Packaging- Availability Magnesium TM Soil Anodes High Potential Magnesium SuperMag High Potential Magnesium Anodes from Galvotec Alloys, Inc. offers typical high workingldriving potentials of -1.70 volts or better vs. copperlcopper

More information

CATHODIC PROTECTION TRANSFORMER RECTIFIER (CPTR)

CATHODIC PROTECTION TRANSFORMER RECTIFIER (CPTR) CATHODIC PROTECTION TRANSFORMER RECTIFIER (CPTR) Fig1. CPTR SMART CONTROL PRECISION CUSTOMIZED MANUAL OR AUTO SCR OR DIODE DRY TYPE SWITCH MODE DRY TYPE SCR OR DIODE OIL TYPE 1 INDEX PAGE 1. Cover 2. Index

More information

Science AS90191 Describe Aspects of Physics.

Science AS90191 Describe Aspects of Physics. Circuits and components Science AS90191 Describe Aspects of Physics. An electric current is the movement of electrons (negatively charged particles). A circuit is made up of components connected together

More information

= V peak 2 = 0.707V peak

= V peak 2 = 0.707V peak BASIC ELECTRONICS - RECTIFICATION AND FILTERING PURPOSE Suppose that you wanted to build a simple DC electronic power supply, which operated off of an AC input (e.g., something you might plug into a standard

More information

Chapter 11 Electron Transfer Reactions and Electrochemistry

Chapter 11 Electron Transfer Reactions and Electrochemistry Chapter 11 Electron Transfer Reactions and Electrochemistry Introduction Redox, or electron transfer, reactions constitute one of the broadest and most important classes of reactions in chemistry. All

More information

CORROSION BASICS. (from Swain (1996) and Schultz (1997))

CORROSION BASICS. (from Swain (1996) and Schultz (1997)) What is corrosion? CORROSION BASICS (from Swain (1996) and Schultz (1997)) Webster s Dictionary corrode (v.) To eat away or be eaten away gradually, especially by chemical action. NACE Corrosion Basics

More information

Atomic Structure. Atoms consist of: Nucleus: Electrons Atom is electrically balanced equal electrons and protons. Protons Neutrons

Atomic Structure. Atoms consist of: Nucleus: Electrons Atom is electrically balanced equal electrons and protons. Protons Neutrons Basics of Corrosion Performance Metals Sacrificial anode manufacturer Specialize in aluminum alloy anodes All products made in the USA (Berks county, PA) ISO9001/2001 Certified Quality System Also traditional

More information

How to maintain NiMH Battery?

How to maintain NiMH Battery? How to maintain NiMH Battery? NiMH battery outperforms other rechargeable batteries and has higher capacity and less voltage depression. These properties make them ideal for use in high drain devices like

More information

German Cathodic Protection REMOTE MONITORING AND CONTROL

German Cathodic Protection REMOTE MONITORING AND CONTROL German Cathodic Protection REMOTE MONITORING AND CONTROL Michael Kahle / 17-19. October 2011 / 1. NACE-Jubail Industrial Forum 2011 1. Brief introduction of GCP GCP - Competence in Cathodic Corrosion Protection

More information

PROCEDURE: Part A. Activity Series and Simple Galvanic Cells

PROCEDURE: Part A. Activity Series and Simple Galvanic Cells Experiment 21G ELECTROCHEMISTRY: GALVANIC CELLS AND BATTERIES FV 2/8/11 MATERIALS: Ag, Cu, Zn strips; sandpaper; 20d bright common nails (2); 0.25 M solutions of AgNO 3, Cu(NO 3 ) 2, Zn(NO 3 ) 2 ; 1.0

More information

TECHNICAL SERVICE DEPARTMENT Technical Service Bulletin 1-800-432-8373. Anode Rods, Cathodic Protection and the Porcelain (glass) Lining

TECHNICAL SERVICE DEPARTMENT Technical Service Bulletin 1-800-432-8373. Anode Rods, Cathodic Protection and the Porcelain (glass) Lining Corrosion can be defined as the destructive attack of a metal by an electrochemical reaction with its environment. Steel exposed to moisture and oxygen will rust and corrode. Corrosion is defined as the

More information