Corrosion & Cathodic Protection

Corrosion & Cathodic Protection
in Petroleum Industry Delta consulting 12-16 November, 2006

Corrosion Control Techniques
5.Cathodic Protection Cathodic protection Delta consulting

5.Cathodic Protection 2- Impressed current system DC source Ground bed Drain Point I Umbrella Fe Anode DC Delta consulting

5.Cathodic Protection Basics of Impressed current system Results: 1- The nail at +ve terminal Corrodes 2- The nail at –ve terminal remains Uncorroded Steel nails fixed to dry battery terminals The steel nails immersed in saline water Delta consulting

5.Cathodic Protection Impressed current system Nothing happens since the nails are in different electrolytes Delta consulting

Corrosion Control Techniques Transformer Rectifiers (T/R)
5.Cathodic Protection Transformer Rectifiers (T/R) AC input Voltage, Single/ three phase, Frequency DC maximum output Amp, Volt Air Cooled: with sun-shade Oil Cooled: with thermometer Location: according to area classification Explosion proof (hazardous area) Non-explosion proof (non-hazardous area) Delta consulting

Corrosion Control Techniques Transformer Rectifiers
5.Cathodic Protection Transformer Rectifiers T/R with sun-shade Delta consulting

5.Cathodic Protection Transformer Rectifiers Explosion-proof Wall-mounted/indoors Pole-mounted Delta consulting

Corrosion Control Techniques Transformer Rectifier
5.Cathodic Protection Transformer Rectifier Direct Current Alternating Current Delta consulting

5.Cathodic Protection Common Impressed current anodes: Consumable Anodes Non Consumable Anodes Mixed Metal Oxide (MMO) Platinized Graphite Si – Fe Si – Cr – Fe Delta consulting

5.Cathodic Protection Common Impressed current anodes: Si – Fe Si – Cr – Fe Delta consulting

5.Cathodic Protection Fe Si Anodes Are the most common impressed current anodes Are used in soil, water or sea water Come in two grades; FeSi and FeSiCr for sea water applications Cable connection to anode shall be handled with great care. Delta consulting

5.Cathodic Protection Common Impressed current anodes: Mixed Metal Oxide (MMO) Anodes MMO is an electrically conductive coating that is applied onto a Titanium substrate in order to make it act as an Anode Delta consulting

5.Cathodic Protection Common Impressed current anodes: Mixed Metal Oxide (MMO) Anodes MMO Coating Delta consulting

5.Cathodic Protection Common Impressed current anodes: Graphite Anodes Delta consulting

5.Cathodic Protection Common Impressed current anodes: Platinized Anodes Delta consulting

5.Cathodic Protection Impressed current anodes are some times packaged with the Carbonaceous backfill. Delta consulting

5.Cathodic Protection Installation of CP Systems Impressed Current CP Systems Delta consulting

5.Cathodic Protection Types of ground beds: Deep-well GB Horizontal shallow GB Distributed Anodes Delta consulting

5.Cathodic Protection Deep well > 50m depth Non-metallic vent tube Sand topping Carbonaceous backfill for anodes section Delta consulting

5.Cathodic Protection Carbonaceous backfill Property 218-L 4518 Resistivity, ohm-inch 0.02 0.01 Resistivity, ohm-cm 0.05 0.03 Carbon (L.O.I. method) 99.0 99.9% Moisture 0.10% 0.02% Ash 0.35% VCM 0.30% 0/22% Sulfur 3.75% 4.3% Bulk Density (lbs/ft3) 46-50 62-66 General Sizing + 4 Mesh + 8 Mesh - 8 Mesh +4M < 10% +8M > 90% -8M < 10% 4M 10% +20M > 80% -20M 10% Delta consulting

5.Cathodic Protection Deep-well ground beds Non-metallic Perforated Casing Delta consulting

5.Cathodic Protection Shallow Bed Depth 3 – 5 m Delta consulting

5.Cathodic Protection Delta consulting

5.Cathodic Protection Distributed Impressed Current Anodes Arrangement Delta consulting

5.Cathodic Protection Anode Connection : Anodes cables are connected to anode / positive junction box Each anode can be connected via a variable resistance to control the current output A header cable connects the PJB to e +ve terminal of T/R Delta consulting

5.Cathodic Protection Anode Connection : Direct connection to +ve bus bar Anode Cables from GB Main Cable to +ve Terminal of T/R Positive Junction Box Delta consulting

5.Cathodic Protection Anode Connection : Connection via variable resistance Anode Cables from GB Main Cable to +ve Terminal of T/R Positive Junction Box Delta consulting

5.Cathodic Protection Typical Impressed Current System Arrangement Ground Bed Delta consulting

5.Cathodic Protection Positive current flux through soil to buried pipeline and resulting distribution of current density on pipe wall Delta consulting

Corrosion Control Techniques Pipeline attenuation and
5.Cathodic Protection Pipeline attenuation and multiple ground beds V vs CSE GB GB GB3 Delta consulting

Corrosion Control Techniques Typical Under-Tank Cathodic Protection
System for New Tanks Delta consulting

5.Cathodic Protection Under tank cathodic protection MMO anode grid Delta consulting

5.Cathodic Protection Main Problem with Under-Tank CP Systems The protective +ve CP current causes decomposition of water Since water content of the soil underneath the tank is very limited As a result, the GB dries up – i.e. no electrolyte – and the CP system is aborted Delta consulting

Corrosion Control Techniques Laser Slotted PVC Tubes
5.Cathodic Protection Solution Installation of Under-Tank Watering System Concrete Ring Slotted PVC Pipes Compacted Soil Laser Slotted PVC Tubes Delta consulting

5.Cathodic Protection Installation of Under-Tank Watering System ICCP Anode Grit Tank PVC Watering Pipe To T/R Compacted Soil Delta consulting

5.Cathodic Protection Peripheral Anode Cathodic Protection System for Existing Tanks Horizontal GB MMO strip anode Existing Tank Protecting outermost bottom Delta consulting

Corrosion Control Techniques Cathodic Protection System
Distributed Anode Cathodic Protection System Delta consulting

Corrosion Control Techniques installation for a well
5.Cathodic Protection Cathodic protection installation for a well casing Delta consulting

5.Cathodic Protection Impressed Current Cathodic Protection for Tank Internals Hanging ICCP anode Delta consulting

5.Cathodic Protection Anode Cable extended to outside along vent tube Impressed Current Cathodic Protection for Tank Internals ICCP anode PVC Support Delta consulting

5.Cathodic Protection ICCP for jackets 1- Hanging Anodes Delta consulting

5.Cathodic Protection ICCP for jackets 2- Sub-sea Sleds Delta consulting

Corrosion Control Techniques Cathodic Protection Criteria
7 14 Potential 2.0 1.6 0.8 1.2 -0.4 0.4 0.0 -1.6 -0.8 -1.2 Immunity Fe3+ Passivity Corrosion pH Fe2+ Pourbaix diagram showing the theoretical conditions for corrosion, passivation, and immunity of iron in water and dilute aqueous solutions Delta consulting

5.Cathodic Protection Fe-to-Soil Potential in Low Resistivity Soils showing the degree of corrosion Description Potential vs Cu/CuSO4 mV -500 Free Corrosion -700 Zone of Cathodic Protection -900 Intense Corrosion -600 Sever Over-Protection Problems -1200 Increased Over-Protection -1100 Some Over-Protection -1000 Some Protection -800 The value – 850 mV is the CP criterion for protecting steel in aggressive soils Delta consulting

5.Cathodic Protection Excessive negative potentials can cause : Cathodic Disbonding : i.e. loss of adhesion between the coating and the metal surface Hydrogen Damage : due hydrogen evolution at –ve potentials Delta consulting

Corrosion Control Techniques Potential criterion (mV)
5.Cathodic Protection Potential criteria for cathodic protection of some metals and alloys at 25º C (1) According to British code of practice No. CP 1021, August 1973. But not more negative than about -1.2 Volts. Metal/ Alloy Potential criterion (mV) vs Cu/ Cu SO4 Iron, steel, stainless steel: Aerobic conditions Anaerobic conditions -850 -950 Lead -600 Copper -500 Aluminum -950 (2) Delta consulting

5.Cathodic Protection According to ISO Part 1, 2003 concerning the CP protection criteria of On-Land Pipelines : “The CP system shall be capable of : polarizing all parts of the buried pipeline to potentials more negative than – 850 mV referred to CSE, & to maintain such potentials throughout the design life of the pipeline”. Delta consulting

5.Cathodic Protection According to ISO Part 1, 2003 concerning the CP protection criteria of On-Land Pipelines : “For pipelines operating in soils with very resistivity, a protection potential more positive than – 850 mV referred to CSE may be considered, e.g. as follows”: - 750 mV for 10,000 < p < 100,000 ohm.cm - 650 mV for p ,000 ohm.cm > i.e., the value of – 850 mV is only for soils with p < 10,000 ohm.cm p = Soil Resistivity Delta consulting

Corrosion Control Techniques Potential Measurement
5.Cathodic Protection Cathodic protection monitoring Potential Measurement Structure/Electrolyte Potential is measure by means of a reference electrode : Copper / Copper Sulfate Soil Silver / Silver Chloride Sea Water Delta consulting

Corrosion Control Techniques Copper / Copper Sulfate
5.Cathodic Protection Copper / Copper Sulfate reference electrode Portable Type Delta consulting

Corrosion Control Techniques Copper / Copper Sulfate
5.Cathodic Protection Copper / Copper Sulfate reference electrode In order to measure the structure – to – soil potential , the CSE must become part of the soil This is fulfilled by inter-mixing of the CSE content with the soil content due to diffusion down a concentration gradient Delta consulting

5.Cathodic Protection H2O ( SO42- Soil) Copper Rod CuSO4 Saturated Water molecules migrate into CSE Sulfate ions migrate from CSE to soil Porous Disc AVO meter Typical Arrangement for Pipe – to – Soil Measurement Solution HIGH WATER CONTENT HIGH SO42- IONS CONTENT Pipe Cu Cu2+ Delta consulting

5.Cathodic Protection Typical Arrangement for Pipe – to – Soil Measurement Icp umbrella CSE Delta consulting

5.Cathodic Protection IR error Ep CP current soil surface Coating Eon Reading Eon = Ep + IR Error Voltmeter Voltmeter Delta consulting

5.Cathodic Protection Ep soil surface Coating Eoff Reading , instantaneous Eoff = Ep Voltmeter Voltmeter Delta consulting

5.Cathodic Protection Permanent Copper / Copper Sulfate reference electrode Prepackaged CSE Backfill : Gypsum + Bentonite clay + Sodium sulfate Delta consulting

5.Cathodic Protection Test Posts for CP Monitoring Flush – to – ground Delta consulting

4.Cathodic Protection Electrode Placement For pipelines : every Km destination For tanks : preferred under tank or closest Delta consulting

5.Cathodic Protection CP Permanent Monitoring ( Test ) Point consists of :- Permanent Reference Electrode ( or Portable type ) Test Post : for pipelines every Km intervals for tanks : near the tank Delta consulting

5.Cathodic Protection Structure-to-Soil potential measurement using Voltmeter. Delta consulting

5.Cathodic Protection Permanently Installed Reference Electrode & Test Post Delta consulting

5.Cathodic Protection Permanent Monitoring for Under Tank Cathodic Protection Tank Diameter (m) No. of Electrodes Required 5-10 1 10-23 2 23-36 3 45 and above 4 Delta consulting

5.Cathodic Protection Reference Electrodes Locations for Under - Tank CP Systems 1/4D 1/6D 2/6D 2/8D 3/8D 1/8D D=45m and above D=23-36m D= m D=5-10m Key : Reference Electrode Delta consulting

5.Cathodic Protection PVC Pipe Under Tank Soil Concrete Ring CSE PVC pipe installed through the concrete different locations for CSE placement. Concrete Ring Under Tank Soil PVC Pipe – See Details Top View Delta consulting

5.Cathodic Protection CSE Perforated PVC Pipe Filled with Water Tank Perforated PVC Pipe Installed for Reference Electrode Placement AVO Delta consulting

5.Cathodic Protection Correct method for measuring structure potentials when surface is covered with concrete or asphalt. AVO CSE in Wet Soil Buried Pipe Concrete / Asphalt Delta consulting

5.Cathodic Protection For monitoring tank’s internal CP system use: Hanging RE ( from roof ) Plug RE ( fixed on shell ) RE Hanging Reference Electrodes Plug RE Delta consulting

5.Cathodic Protection Potential Measurement of jackets / platform legs Diver with portable reference electrode Delta consulting

5.Cathodic Protection Potential Measurement of jackets / platform legs Transponder CP monitoring Delta consulting

Corrosion Control Techniques Potential plot after data
5.Cathodic Protection Potential plot after data analysis Delta consulting

5.Cathodic Protection Potential Measurement of subsea pipelines Trailing-wire potential survey Delta consulting

5.Cathodic Protection Potential Measurement of well casing Delta consulting

5.Cathodic Protection Cable Connections Cable – to - cable connection Cable – to - pipe connection Cable – to - structure connection Delta consulting

5.Cathodic Protection Cable Connections Splice Kit : for cable-to-cable connection 1 2 Araldite is poured & let to dry Delta consulting

5.Cathodic Protection Cable Connections For cable-to-pipe connection : 1- Thermite ( Cad / Exothermic ) Welding 2- Pin Brazing 3- Mechanical connection ( for gas pipelines ) Delta consulting

5.Cathodic Protection Crucible Disks Cartridge Cable Connections For cable-to-pipe connection 1- Thermite Welding : Spark Flint Delta consulting

5.Cathodic Protection Thermite Welding Prior to welding : The coating must be removed at welding point ( 5x5 cm square ) Metal surface to be polished and cleaned Thermite Weldment Delta consulting

5.Cathodic Protection Protecting the Thermite Weldment 1 2 3 Self-adhesive Handy-cap Delta consulting

5.Cathodic Protection Cable Connections For cable-to-pipe connection 2- Pin Brazing : emits less heat output Pin Brazing Unit Pistol / Gun Pins & Ferrules Lug Grinder Delta consulting

5.Cathodic Protection Cable Connections For cable-to-pipe connection 2- Pin Brazing Delta consulting

5.Cathodic Protection Cable Connections For cable-to-pipe connection 2- Pin Brazing 1 Clean the surface 2 Load gun with pin & ferrule 3 pin braze 4 Test connection Delta consulting

5.Cathodic Protection Cable Connections For cable-to-pipe connection 3- Mechanical Connection : recommended for drain point connection of gas pipelines Delta consulting

5.Cathodic Protection Cable Connections Terminal Lugs : for cable-to-structure ( tank ) connection Delta consulting

4.Cathodic Protection Electrical Isolation Structures to be protected shall be electrically isolated from portions which do not require protection. Electrical isolation is made by : Isolating flange kit ( IFK ) IFK is Aboveground / Underground Interface Delta consulting

4.Cathodic Protection Electrical Isolation Isolating flange kit ( IFK ) Delta consulting

4.Cathodic Protection Isolating flange kits In hazardous areas , IFK’s are protected by means of Spark Gaps Spark Gap Fitted Delta consulting

4.Cathodic Protection Electrical Isolation Monolithic Blocks Delta consulting

4.Cathodic Protection The monolithic blocks are protected against electrostatic charges and lightening by polarization cell Monolithic Blocks + Polarization Cell Delta consulting

4.Cathodic Protection Casings for Road Crossings Delta consulting

5.Cathodic Protection Casings for Road Crossings There should NOT be any contact between the pipe & casing Test posts usually crossings to monitor the potential of pipe and casing separately Delta consulting

4.Cathodic Protection Clamp Meter Clamp Meters are used to check: electric cables integrity current output of each anode Clamp Meter Delta consulting

5.Cathodic Protection Pipeline & Cable Warning Markers Delta consulting

5.Cathodic Protection CP System Design Delta consulting

5.Cathodic Protection There are numerous codes and references that shall be referred to when dealing with cathodic protection among these are: NACE RP 0169 NACE RP 0176 NACE RP 177 NACE RP 575 ISO , PART I – 2003, “On-land Pipelines” ISO , PART II – 2004, “Offshore Pipelines” DnV RP B 401 API 651 J. Morgan, “Cathodic Protection” A.W. Peabody, “Control of Pipeline Corrosion” Delta consulting

Corrosion Control Techniques 5.Cathodic Protection Design
Terms & Definitions Natural Potential: Is potential of structure to be protected whenever no cathodic protection system is applied. Protection Potential: Is the potential of structure to be protected whenever corrosion rate is insignificant. Anode Backfill: Materials with low resistivity surrounding buried anode, may be moisture retaining materials, used for decrease anode to electrolyte resistance and prevent anode polarization. Delta consulting

Terms & Definitions Drain Point: Location of negative cable connection to the structure to be protected through which the cathodic protection current returns to its source. Coating Break-down Factor: Is the ration between the current density required to polarize coated surface and density required to polarize bare surface. Initial Current Density Estimated current density required for polarization of structure to be protected at the start of the lifetime. Final Current Density: Estimated current density required to maintain polarization at the end of the lifetime. Delta consulting

Terms & Definitions Mean Current Density: Estimated current density for the entire of the lifetime Anode Electro-chemical Capacity: The amount of electricity expressed by (Amper.Hour/kg) that is produced due to anode consumption. Cathodic Protection Criteria: Limits of protection potentials. Delta consulting

5.Cathodic Protection CP System Design : Basic information for design considerations Type of electrolyte (environment) Soil Fresh/ saline water. Availability of power supply Temperature Type of coating For pipelines: Pipeline route Crossings (foreign pipeline, roads, rivers, etc.) Presence of high transmission power lines Presence of foreign metallic structures. Delta consulting

Corrosion Control Techniques Soil resistivity (ohm.cm)
5.Cathodic Protection Soil resistivity Soil represents the electrolyte Soils with low resistivity have high conductivity; i.e. corrosive NACE ranking : Soil resistivity (ohm.cm) Corrosivity up to 1,000 Severely corrosive 1,000-5,000 Corrosive 5,000-10,000 Moderately corrosive 10,000-20,000 Slightly corrosive 20,000 and above Non-corrosive Delta consulting

5.Cathodic Protection Four-Terminals (Wenner) Method : For Measurement of Soil Resistivity. Kit Power Unit Stainless Steel Pins Cables Delta consulting

5.Cathodic Protection 4-Terminals Arrangement a Depth = a Ohm’s Low : R = V/I R : Resistance (ohm) V : Applied Voltage I : Recorded Amperage Delta consulting

Current demand for CP: Current density : it is the current required to polarize (1 meter)2 of bare steel in a given electrolyte. Current density increases with increasing temperature Delta consulting

Temperature : current demand shall be increased by 25% per every 10º C incremental rise above 30º C. This requirement is described by the following equation: i = i0 + [i0 x 0.25 (t - t0)] / 10 Where, i = current density at operating temperature, Amp/m2 i0 = base current density at standard temperature t = operating temperature ºC t0 = standard temperature (30ºC) Delta consulting

5.Cathodic Protection Current density determined in mA/m2 is dependant on the media aggressivity. Therefore if soil resistivity is low then current density shall be high Media Current Density mA/m2 Aggressive Soil 10 Normal soil 5 Sea water 90 Fresh water 30 Delta consulting

5.Cathodic Protection Power Supply : The T/R is fed with AC current from the nearest power supply. If there is no power supply available, Solar Units to be used instead of T/R. Delta consulting

5.Cathodic Protection 240 Watt Solar Array 0-24 Volt Delta consulting

5.Cathodic Protection GB Pipe to be protected Converter Regulator Batteries Junction Box Solar Modules Structure (-) (+) Typical Arrangement for ICCP Using Solar Energy Sun Delta consulting

5.Cathodic Protection Typical Coating Resistances for various coating qualities Coating quality Range of specific leakage resistance (RC), ohm.m2 Poor 1,000-2,500 Fair 5,000-10,000 good 25,000-50,000 Excellent 100, ,000 Delta consulting

5.Cathodic Protection CP current Typical Coating Breakdown Values Coating type % breakdown Initial Mean Final Thick coating ≤ 1 5 10 Epoxy coal tar ≤ 2 5-10 10-20 Fusion bonded epoxy 1-2 5-20 Polypropylene (25 yrs) 0.5 2 Polyethylene (25 yrs) 1 3 Delta consulting

5.Cathodic Protection Recommended potential limits for different coatings to avoid coating disbondment Coating type Volt (vs Cu/ CuSO4) Asphalt Enamel -2 Epoxy coal tar -1.5 Fusion bonded epoxy Tape wrap Polyethylene -1.0 Delta consulting

5.Cathodic Protection Pipeline Route Cross-country P/L’s pass through different types of soils, i.e. different electrolytes Presence of high voltage power transmission lines Delta consulting

5.Cathodic Protection Pipeline Route Delta consulting

5.Cathodic Protection Pipeline AC interference from electromagnetic field Delta consulting

5.Cathodic Protection For protection against stray current from high tension lines, zinc ribbon and polarization cells are used Delta consulting

5.Cathodic Protection Stray current interference In case of pipe-crossing of cathodically protected pipelines BONDING is required by means of : Solid boning, or Resistance bonding Delta consulting

5.Cathodic Protection Stray-current corrosion Pipeline potential shifts in cathodic direction ( more negative values ) Possibility of coating disbondment and hydrogen damage Pipeline potential shifts in anodic direction ( more positive values ) Possibility of high anodic current densities , i.e. high corrosion rates Delta consulting

5.Cathodic Protection Stray-current corrosion Delta consulting

Corrosion Control Techniques Basic Cathodic Protection Calculations
Delta consulting

5.Cathodic Protection CP Current Requirement CD= S x a x CBDC Delta consulting

5.Cathodic Protection Impressed Current (On-land) Systems Anodes Weight & Quantity Requirement Delta consulting

5.Cathodic Protection CP Circuit Resistance : (ICCP systems) Delta consulting

5.Cathodic Protection CP Ground-Bed Resistance : Delta consulting

5.Cathodic Protection CP Ground-Bed Resistance (cont’) : Delta consulting

5.Cathodic Protection CP Ground-Bed Resistance : Delta consulting

5.Cathodic Protection CP Cables Resistance : Delta consulting

5.Cathodic Protection CP Circuit Resistance & Driving Voltage : (ICCP systems) Delta consulting

5.Cathodic Protection Transformer/Rectifier (T/R) Rating: T/R Output Rating: Select near standard T/R rating: (e.g. 12V, 24V, 36V, 48V, 5A, 10A, 15A, 20A…etc) T/R output: 15A/24V DC T/R Input Characteristics: Check available electrical power characteristics: Either 3PH, 400V AC, 50Hz Or PH, 230V AC, 50Hz T/R Input: 3PH, 400V AC, 50Hz Delta consulting

5.Cathodic Protection CP Current Attenuation (Spread) Check (for Pipelines) Delta consulting

5.Cathodic Protection Typical Coating Resistance (for various coating qualities) Coating quality Range of specific leakage resistance (Rl), ohm.m2 Poor 1,000-2,500 Fair 5,000-10,000 good 25,000-50,000 Excellent 100, ,000 Delta consulting

5.Cathodic Protection Sacrificial Anode Systems CP Current Requirement CD= S x a x CBDC Delta consulting

5.Cathodic Protection Anode Material & Dimensions Selection Anode Material Selection Delta consulting

5.Cathodic Protection Anodes Weight & Quantity Requirement Delta consulting

4.Cathodic Protection Sacrificial VS Impressed Current CP Sacrificial Impressed current No need for external power source Requires an external power source Easy to design and install Requires skillful design and installation uncontrollable Can be controlled Used only for limited surface areas and well coated structures Can be used for uncoated surfaces and used for any surfaces Has no detrimental effects Can cause serious problems if not handled carefully Is limited to low resistivity can be used at any resistivity Low maintenance High maintenance Delta consulting

5.Cathodic Protection Sacrificial VS Impressed Current CP Delta consulting

Thank You and Good Luck Delta consulting

Corrosion & Cathodic Protection

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Corrosion & Cathodic Protection

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