WESTERN REGION GAS CONFERENCE AUGUST 21, 2012 CORROSION 101 BASIC CORROSION MADE CLEAR AS MUD PRESENTED BY John Brodar P.E. of the Salt River Project

Just as Fire requires all three conditions (Fuel, Oxygen and an Ignition Source) to burn, several conditions must be present for Corrosion to occur. Corrosion requires an anode, a cathode, an electrolyte and a metallic path connecting the anode and cathode. If any one of these conditions is not present or prevented, corrosion will not occur. Corrosion is electrochemical in nature: the electrolyte and metallic path are necessary for current to flow. If there is no current flow there is no corrosion.

ACME CAME MECA ECAM … REMOVE ANYONE AND THERE IS NO CORROSION.

STOP CORROSION. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

STOP CORROSION. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

STOP CORROSION. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

STOP CORROSION. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

STOP CORROSION. REMOVE THE ANODE REMOVE THE CATHODE REMOVE THE METALLIC PATH REMOVE THE ELECTROLYTE AND YOU STOP CORROSION.

WHAT MAKES SOMETHING AN ANODE?

WHAT MAKES SOMETHING AN ANODE? WHAT MAKES SOMETHING A CATHODE?

WHAT MAKES SOMETHING AN ANODE. WHAT MAKES SOMETHING A CATHODE WHAT MAKES SOMETHING AN ANODE? WHAT MAKES SOMETHING A CATHODE? DIFFERENCES!

WHAT MAKES SOMETHING AN ANODE. WHAT MAKES SOMETHING A CATHODE WHAT MAKES SOMETHING AN ANODE? WHAT MAKES SOMETHING A CATHODE? DIFFERENCES!

WHAT MAKES SOMETHING AN ANODE. WHAT MAKES SOMETHING A CATHODE WHAT MAKES SOMETHING AN ANODE? WHAT MAKES SOMETHING A CATHODE? DIFFERENCES!

WHAT MAKES SOMETHING AN ANODE. WHAT MAKES SOMETHING A CATHODE WHAT MAKES SOMETHING AN ANODE? WHAT MAKES SOMETHING A CATHODE? DIFFERENCES!

Illustration of Ohm’s Law _ + E = 1 volt R = 1000 ohms I

Illustration of Ohm’s Law _ + E = 1 volt R = 1000 ohms I

Illustration of Ohm’s Law _ + E = 1 volt R = 1000 ohms I

Illustration of Ohm’s Law _ + The “I” is conventional current. I

Illustration of Ohm’s Law _ + The “I” is conventional current. Conventional current always leaves the positive side of the battery. I

Illustration of Ohm’s Law _ + The “I” is conventional current. Conventional current always leaves the positive side of the battery. I In Cathodic Protection the direction of conventional current is incredibly important!

Electrochemical Circuits Metallic Path Metallic Path e - + ions + ions A A C C  - ions ions Electrolytic Path Electrolytic Path Conventional Current Flow Conventional Current Flow

Components of a Corrosion Cell Anode (oxidation reaction) corrosion Cathode (reduction reaction) no corrosion Electrolyte (cations and anions) External path (usually metallic)

Electron and Ion Flow + Direction of Electron Flow e CATHODE ANODE e- ELECTROLYTE e - e- Direction of Electron Flow CATHODE ANODE

Electron and Ion Flow + Direction of Electron Flow e CATHODE ANODE e- ELECTROLYTE e - e- Direction of Electron Flow CATHODE ANODE Direction of Conventional Current Flow

Direction of Conventional Current Flow + ELECTROLYTE e - e- Direction of Electron Flow CATHODE ANODE Direction of Conventional Current Flow

IN THE ELECTROLYTE, AS CONVENTIONAL CURRENT LEAVES THE ANODE IT TAKES IRON IONS INTO SOLUTION: CORROSION OCCURS

Anodic Process (half reaction) Fe++ e- ANODE ELECTROLYTE

AS CONVENTIONAL CURRENT LEAVES THE ANODE IN THE ELECTROLYTE CORROSION OCCURS + ELECTROLYTE e - e- Direction of Conventional Current Flow CATHODE ANODE

Illustration of Ohm’s Law _ + The “I” is conventional current. Conventional current always leaves the positive side of the battery. I In Cathodic Protection the direction of conventional current is incredibly important!

Voltmeter Circuit Connection + _ VOLTS Parallel Connection RA RB RC E I

Voltage Sign Current + _ Voltage measurement is positive 20 mV

Potential Measurement Between Two Reference Electrodes + Reading + _ Reference Electrode Voltmeter with Current

Sign of Voltage for Dissimilar Metals Noble Active + _ Voltage measurement is positive .600 V

Sign of Voltage for Dissimilar Metals Noble Active + _ Voltage measurement is positive .600 V ANODE NEGATIVE -OXIDATION RUST LOSE ELECTRONS LOSE POSITIVE IONS GAIN NEGATIVE IONS CATHODE POSITIVE + REDUCTION DOES NOT RUST GAINS ELECTRONS GAINS POSITIVE IONS REPELS NEGATIVE IONS

Electrochemical Circuits Metallic Path Metallic Path e - + ions + ions A A C C  - ions ions Electrolytic Path Electrolytic Path Conventional Current Flow Conventional Current Flow

Voltmeter Connections

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND?

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON)

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON) COPPER

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON) COPPER GALVANIZED STEEL (ZINC)

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON) COPPER GALVANIZED STEEL (ZINC) MAGNESIUM

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? STEEL (IRON) COPPER GALVANIZED STEEL (ZINC) MAGNESIUM

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? WHICH IS AN ANODE?

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? WHICH IS AN ANODE? WHICH IS A CATHODE?

WHAT ARE THE FOUR MOST COMMONLY USED METALS UNDERGROUND? WHICH IS AN ANODE? WHICH IS A CATHODE? ALL OF THEM CAN BE EITHER!

STEEL (IRON) COPPER GALVANIZED STEEL (ZINC) MAGNESIUM DID YOU KNOW THAT EACH OF THESE METALS HAS A DIFFERENT NATURAL VOLTAGE OR POTENTIAL? STEEL (IRON) COPPER GALVANIZED STEEL (ZINC) MAGNESIUM

COMPARE OTHER METALS TO STEEL INTRODUCE THE REFERENCE CELL TYPICAL POTENTIALS RELATIVE TO CSE

Reference Electrodes (Half Cells)

Portable Reference Electrodes

Copper-Copper Sulfate Reference Electrode Connection for Test Lead Removal Cap Copper Rod Clear Window Saturated Copper Sulfate Solution Porous Plug Undissolved Copper Sulfate Crystals

CORROSION IS AN ELECTRO-CHEMICAL PHENOMENON CORROSION IS AN ELECTRO-CHEMICAL PHENOMENON. IN WATER IMMERSION SERVICE IT IS RELATIVELY EASY, UNDER SOME CONDITIONS, TO WORK WITH THE CHEMICAL PORTION OF THIS PHENOMENON.

ITS CALLED WATER TREATMENT AND IS USED IN MANY DIFFERENT INDUSTRIES.

CORROSION IS AN ELECTRO-CHEMICAL PHENOMENON CORROSION IS AN ELECTRO-CHEMICAL PHENOMENON. IN WATER IMMERSION SERVICE IT IS RELATIVELY EASY, UNDER SOME CONDITIONS, TO WORK WITH THE CHEMICAL PORTION OF THIS PHENOMENON. UNDERGROUND IT IS VERY DIFFICULT TO WORK WITH THE CHEMICAL PORTION. THAT’S WHY IT IS SO IMPORTANT TO UNDERSTAND AND BE ABLE TO WORK WITH THE ELECTRICAL PORTION.

LET’S LOOK AT IRON

WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME

WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE

WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE THE IRON IS NO LONGER CALLED AN ATOM IT IS NOW AN ION WITH A PLUS TWO VALIANCE.

WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE THE IRON IS NO LONGER CALLED AN ATOM IT IS NOW AN ION WITH A PLUS TWO VALIANCE. THE IRON ION NO LONGER STICKS TO THE OTHER IRON ATOMS, IT GOES INTO SOLUTION.

WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE THE IRON IS NO LONGER CALLED AN ATOM IT IS NOW AN ION WITH A PLUS TWO VALIANCE. THE IRON ION NO LONGER STICKS TO THE OTHER IRON ATOMS, IT GOES INTO SOLUTION. THE IRON ATOM CORRODES AND THE CORROSION PRODUCT IS AN IRON ION.

PRESENTED BY John Brodar P.E. of the Salt River Project CORROSION 101 FREE SAMPLES: LET’S MAKE RUST PRESENTED BY John Brodar P.E. of the Salt River Project

WHEN AN IRON ATOM CORRODES SEVERAL THINGS HAPPEN AT THE SAME TIME THE IRON ATOM GIVES OFF TWO ELECTRONS AND BECOMES POSITIVE THE IRON IS NO LONGER CALLED AN ATOM IT IS NOW AN ION WITH A PLUS TWO VALIANCE. THE IRON ION NO LONGER STICKS TO THE OTHER IRON ATOMS, IT GOES INTO SOLUTION. THE IRON ATOM CORRODES AND THE CORROSION PRODUCT IS AN IRON ION.

++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++

++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ WHEN WILL THIS END? ++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++

++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++ WHAT CAN WE DO? ++ ++ ++ ++ ++ ++ ++ ++ +++ ++ ++ ++ ++ ++ ++ ++ ++ ++ ++

YOU’RE RIGHT. THE FIRST LINE OF DEFENSE AGAINST CORROSION IS COATINGS. THEY ARE RELATIVELY CHEAP AND AMAZINGLY EFFECTIVE. EXCEPT..

COATINGS ARE EFFECTIVE EXCEPT AT HOLIDAYS (COATING DEFECTS AT THE TIME OF APPLICATION). OR AT DAMAGED AREAS. DAMAGE MAY OCCUR DURING MANUFACTURE, TRANSPORTATION, INSTALLATION OR IN SERVICE.

HOW BAD CAN THE CORROSION AT A DAMAGED AREA OF THE COATING BE?

FARADAY’S LAW FOR STEEL FARADAY’S LAW SAYS THAT ONE AMPERE OF CURRENT FLOWING OFF OF STEEL FOR ONE YEAR WILL CAUSE THE CORROSION OF 20 POUNDS OF STEEL.

FARADAY’S LAW IS VERY MUCH A MATHEMATICAL RELATIONSHIP FARADAY’S LAW IS VERY MUCH A MATHEMATICAL RELATIONSHIP. ½ AMP FOR ONE YEAR WILL CONSUME 10 POUNDS OF STEEL ½ AMP FOR TWO YEARS WILL CONSUME 20 POUNDS OF STEEL 2 AMPS FOR ½ YEAR WILL CONSUME 20 POUNDS OF STEEL

CURRENT FLOWING OFF OF YOUR PIPELINE WILL CONSUME STEEL. HOW MUCH DOES A ½” DIAMETER HOLE IN A ¼” WALL PIPE WEIGH? NOT MUCH! JUST 0.0558 LBS.

HOW MUCH CURRENT DOES IT TAKE TO MAKE THAT ½” HOLE? 1 YEAR @ 0.0028 AMPS 2 YEARS @ 0.0014 AMPS OR 1.4 MILLIAMPS 5 YEARS @ 0.6 ma 10 YEARS @ 0.28 ma that’s little more than ¼ ma

Why coatings?

BECAUSE COATINGS ARE THE CHEAPEST THING WE CAN DO TO STOP CORROSION. Why coatings? BECAUSE COATINGS ARE THE CHEAPEST THING WE CAN DO TO STOP CORROSION.

Why cathodic protection?

Why cathodic protection? Since coatings are not perfect we have to do something to protect the holidays and damaged areas. AND

Why cathodic protection? CATHODIC PROTECTION IS THE EASIEST THING TO DO TO A PIPELINE AFTER IT IS INSTALLED.

DEMO PROTECTED PIPE

Microscopic View of a Corrosion Cell Anode Cathode Microscopic Corrosion Cell on the Surface of a Pipeline

Cathodic Protection on a Structure (Macroscopic view) Anode Cathode Metallic Connection Electrolyte Cathodic Protection Anode Cathodic Protection Current Applied

Polarization of a Structure -.5 -.6 -.65 -.7 -.58 Native Potentials Corrosion Mitigated -.7 -.58 NATURALLY OCCURING CATHODE. MORE POSITIVE POLARIZATION NATURALLY OCCURING ANODE. MORE NEGATIVE

APPLY (PARTIAL) CATHODIC PROTECTION!! Prepare to duck.

Polarization of a Structure -.5 -.6 -.65 -.7 -.58 Native Potentials Corrosion Mitigated POLARIZATION

APPLY (PARTIAL) CATHODIC PROTECTION!! APPLY MORE CATHODIC PROTECTION

Polarization of a Structure -.5 -.6 -.65 -.7 -.58 Native Potentials Corrosion Mitigated POLARIZATION

APPLY (PARTIAL) CATHODIC PROTECTION APPLY (PARTIAL) CATHODIC PROTECTION!! APPLY MORE CATHODIC PROTECTION APPLY EVEN MORE CATHODIC PROTECTION

Polarization of a Structure -.5 -.6 -.65 -.7 -.58 Native Potentials Corrosion Mitigated POLARIZATION

APPLY (PARTIAL) CATHODIC PROTECTION APPLY (PARTIAL) CATHODIC PROTECTION!! APPLY MORE CATHODIC PROTECTION APPLY SUFFICIENT CATHODIC PROTECTION

Polarization of a Structure -.5 -.6 -.65 -.7 -.58 Native Potentials Corrosion Mitigated POLARIZATION

Cathodic Protection on a Structure (Macroscopic view) Anode Cathode Metallic Connection Electrolyte Cathodic Protection Anode Cathodic Protection Current Applied

Cathodic Protection Cathodic protection is the cathodic polarization of all noble potential areas (cathodes) to the most active potential on the metal surface. Cathodic protection is achieved by making the structure the cathode of a direct current circuit. The flow of current in this circuit is adjusted to assure that the polarized potential is at least as active as the most active anode site on the structure. NACE CP 1 When the potential of all cathode sites reach the open circuit potential of the most active anode site, corrosion on the structure is eliminated. NACE CP2 Slides Cathodic protection is the polarization of the most cathodic areas on a structure to a potential equal to or more negative than the most anodic potential on the structure. When all areas are polarized to a potential equal to or more negative than -850 mv relative to a copper copper sulfate reference electrode, all corrosion has been halted.

DEMO TEST REELS

Close Interval Potential Survey Reading + _ Cu/Cu SO4 Ref. Cell Voltmeter Pipe Electrolyte

CIS Potential Profile

DEMO TWO WIRES

Shunts

Current Shunts Measure voltage drop across a known resistance. Current is calculated using Ohm’s Law.

Shunt Measurement

Current Shunt Calculations #1 Given: Shunt = .01 ohms Voltage across shunt = 50 mV Calculate Current: 1. Convert units of voltage, 50mV = .05 v 2. Calculate current using Ohm’s Law, I = .05 v /.01 ohms = 5 amps

Current Shunt Calculations #2 Given: Shunt = 15 amps 50 millivolts Voltage across shunt = 28 mV Calculate Current: I = 28 mV x 15 amps 50 mV = 8.4 amps

Direction of Current Flow + _ VOLTS RA RB RC E I Current Flow is from Left to Right Up Scale Deflection

Typical Current Measurements There are several current measurements commonly made in cathodic protection surveys: Current output of a galvanic anode system Rectifier current output Test current for determining current requirement of a structure Current on a structure (this is a voltage measurement, and current is calculated) Current across a bond

Current Along a Pipeline

2-Wire Line Current Test

Example of 2-Wire Current Line Calculations Pipe span = 200 feet Pipe is 30-inch weighing 118.7 pounds/ foot Voltage drop across span = 0.17 millivolts Determined resistance of span = 4.88 x 10-4 ohms Calculated current flow = 348 milliamps from west to east

4-Wire Line Current Test Pipe Span for Measuring Current Wires must be color coded 0.17 mV + _ Pipeline Power Source Current Interrupter AMPS VOLTS

CLEARLLY THE 4 WIRE LINE CURRENT TEST IS MORE COMPLEX CLEARLLY THE 4 WIRE LINE CURRENT TEST IS MORE COMPLEX. YOU ONLY HAVE TO DO IT ONCE FOR ANY PARTICULAR PIPE SEGMENT TO DETERMINE THE RESISTANCE. IT IS A MULTI STEP PROCESS.

AFTER YOU BECOME AN OHM’S LAWYER AND CAN WORK WITH E=IR I=E/R R=E/I

YOU WILL UNDERSTAND THAT IF YOU PASS A KNOWN CURRENT AND MEASURE A VOLTAGE YOU CAN USE OHM’S LAW TO CALCULATE RESISTANCE.

ONCE YOU KNOW THE RESISTANCE FOR A SECTION OF PIPE, YOU CAN NOW MEASURE A VOLTAGE DROP AND, AGAIN USING OHM’S LAW, CALCULAE THE ACTUAL CURRENT FLOWING IN THE PIPE.

4-Wire Line Current Test Pipe Span for Measuring Current Wires must be color coded 0.17 mV + _ Pipeline Power Source Current Interrupter AMPS VOLTS

Example of 4-Wire Current Line Calculations Test current = 10 amps Potential shift due to test current (ON= 5.08millivolts and OFF = 0.17 millivolts) = 4.91 millivolts Calibration factor (10/4.91) = 2.04 amps/millivolts Voltage drop across span = 0.17 millivolts Calculated current flow (2.04 x 0.17) = 347 milliamps from east to west

WHY ARE ANODES SOMETIMES NEGATIVE AND SOMETIMES POSITIVE?????

Galvanic Anode Cathodic Protection System

Impressed Current Cathodic Protection

APPLY (PARTIAL) CATHODIC PROTECTION APPLY (PARTIAL) CATHODIC PROTECTION!! APPLY MORE CATHODIC PROTECTION APPLY SUFFICIENT CATHODIC PROTECTION OVER PROTECT A SEGMENT OF PIPELINE

Electrical Shielding due to Shorted Casing Vent Pipe End Seal Casing Pavement Pipe Lying on Casing due to Lack of Insulating Spacers

4-Wire Line Current Test Pipe Span for Measuring Current Wires must be color coded 0.17 mV + _ Pipeline Power Source Current Interrupter AMPS VOLTS

Criteria for Cathodic Protection Cathodic protection is a polarization phenomenon. Cathodic protection is achieved when the open circuit potential of the cathodes are polarized to the open circuit potential of the anodes. Practical application makes use of structure-to-electrolyte potentials.

NACE Standards for Underground or Submerged Iron and Steel SP0169 Control of External Corrosion on Underground or Submerged Metallic Piping Systems SP0285 Corrosion Control of Underground Storage Tank Systems by Cathodic Protection

Criteria for Underground or Submerged Iron or Steel Structures –0.850 volt potential--Negative (cathodic) potential of at least 850 mV with the cathodic protection applied –0.850 volt polarized potential--Negative polarized potential of at least 850 mV 100 millivolts polarization--Minimum of 100 mV of cathodic polarization

Voltage (IR) Drops Across a Measuring Circuit + _ Polarization Film Structure Electrolyte Reference Cell Voltmeter Measurement & C.P. current across electrolyte Resistances Measuring Lead (+) Contact Lead (+)/Ref. Cell Reference Cell Contact Reference Cell to Electrolyte Electrolyte Polarization Structure Contact Test Lead/Structure Test Lead Contact Test/Measuring Lead Measuring Lead (-) Internal Meter

IR Drops Across Electrolyte Reference electrode placement Current interruption

Pipe-to-Soil Potentials -850 mV On IR -850 mV Instant Off or IR Corrected Potential 100 mV Polarization Depolarization + Depolarized Potential t=0 Time