NACE CP2 2023 with 100% correct questions and answers

oxidation loss of electrons, positive charge atoms (anode) reduction gain of electrons, negative charged atoms (cathode) forms of corrosion uniform, crevice, galvanic (dissimilar metals) if two metals have to be couple then best to couple metals close together in the galvanic series, pitting, intergranular, selective leaching (dezincification, graphitization), velocity phenomena, environmental cracking (corrosion fatigue, hydrogen embrittlement, SCC (Carbonates/bicarbonates) High PH Low hydrogen, alkaline, easy polarization Low PH high hydrogen, acidic, harder to polarize High oxygen/High Hydrogen concentration harder to polarize, work at the cathode only, called cathodic depolarizers. factors affecting corrosion A. anything that affects polarization. (temp. etc...) B. concentration cells (oxygen, temp, etc.) In an oxygen concentration cell, what is the anode? (i.e. the area with more or less oxygen?) In a metal ion cell, which area is the anode (i.e. the area with the greater of lower concentration)? C. Anaerobic bacteria (MIC) Absence of oxygen, depolarizer polarization a. corrosion current reduces with polarization b. polarization increases with CP current applied c. Occurs at surface of both anode and cathode. shielding a. shorted casings b. proximity of other structures c. reinforced concrete amphoteric materials corrode at low and high pH on potential native + polarization + IR drop polarized potential (off) native + polarization kirchoff's laws a. voltage (series circuits) b. current (parallel circuits) faraday's law W=KIT relates weight loss of metal in a corrosion cell with time and current flow. rate of corrosion directly proportional to current flow cathodic protection limitations -shielding issues -attenuation -interference -excessive current density -contact with other metals (shorts) measurement methods true voltage reading voltmeter reading % error calculations effect of voltmeter resistance IR correction methods test stations allow electrical connection to structure for potential measurements and bonds. Spans allow current and direction (IR drop). inistall during construction pH measure of acidity(hydrogen ion concentration) high pH is alkaline low pH is acid pH is a log function therefore each increase in pH is a factor of 10. RECTIFIER - positive to anode -negative to structure - AC suppy -AC circuit breaker -Transformer (increase or decrease voltage) -AC fuse -rectifier bridge - diodes change AC to DC -Voltmeter and Ammeter -Surge Protection -Filters Esecondary = (Eprimary x Secondary turns) / primary turns Reference electrode location the reference electrode should be placed as close to the structure as practical. (underground piping or tanks- over the center of the structure, multiple readings along the structure as required) internal surfaces of storage tanks, waterfront and offshore structures (as close to the wall as possible) impressed current vs sacrificial impressed current- higher current, better control sacrificial- no power required, less maintenance, easy to install, less land AC considerations capacitance, inductance, and resistance hazardous AC potential - 15 Vac Safe method of connecting ground0 cable to ground then to pipe arcing hazards corrosion rates from AC (current density) switching or pulse rectifiers Reference cells CuCuSO4- most common, (soil, fresh water) AgAgCL - seawater Calomel- lab Hydrogen - standard (lab) zinc- stationary Cathodic Protection protect the cathode attempts to bring the cathode potential as negative as the anode potential NACE criteria- what are the exceptions? -high temperature -bacteria -sulfides -acid environments -dissimilar metals Isolation Requirement confine protection to protected structure thus limiting the current required for protection. use for stray current with care continuity requirement bonds are necessary for continuity: mechanical fittings (compression, bell & spigot, rebar etc.) Impressed Current Anodes graphite cast iron (high silicon chromium) mixed metal oxides scrap iron conductive polymer cylindrical, tubular soil..... backfilled in coke breeze current span current in a pipe can be measured by taking a voltage drop across a known length and either calibrating the section in question or using resistance from tables. unknown pipe size must be calibrated by using I/ deltamV or R= V/I using 4 wires Sacrificial anode types magnesium zinc cylindrical, bullet, ribbon, bracelet soil backfilled in gypsum, bentonite mixture to reduce contact resistance to soil and to retain moisture make sure to remove plastic shipping bag small anode to large cathode ratio higher corrosion penetration rate large anode to small cathode ratio lower corrosion penetration rate 4 elements of a corrosion cell Anode Cathode Metallic Patch Electrolyte Faraday's law calculates metal lost due to current over time the stability of a copper-copper sulfate reference electrode does not vary with a saturated solution of the copper ions. if a digital meter displays a negative value while measure a voltage across a resistor, it indicates ... Which of the following are depolarizers? i.Dissolved oxygen ii. increased electrolyte velocity iii. bacteria action iv. current pickup on the metal i, ii, iii only polarization occurs a. at the anode surface only b. at the cathode surface only c. at the anode and cathode surfaces d. in the metallic path C. at the anode and cathode surfaces Which of the following factors affect polarization? a. current b. ion concentration c. anode/cathode ratio d. temperature All of the above Which of the following are types of polarization? i. concentration ii. activation iii. temperature iv. velocity i and ii The measure of the electrochemical difference between two metals in an electrolyte is which of the following? a. amps b. volts c. ohms d siemans b. volts the relationship between current and polarization is described by which of the following? i. Corrosion cell current decreases with increased polarization. ii. polarization increases with increased current. iii. current increases with increased polarization iv. polarization decreases with increased current i and ii only a passivating material will exhibit which of the following properties? i. does not corrode at all ii. corrosion increases as current increases initially iii. corrosion current decreases after a certain point. iv. corrosion current increases beyond the passive region ii, iii, and iv only In a standard emf series of metals, which of the following is represented? a. the potential of a metal is measured in a saturated solution of copper-sulfate b. current is measured between the most noble and most active metals. c. the potential is measured with respect to a standard hydrogen electrode. d. the total number of electrons is determined. c. the potential is measured with respect to a standard hydrogen electrode if two different metals are connected together in an electrolyte, the metal with the a. most negative potential is the cathode b. most positive potential is the cathode c. positive potential will corrode d. highest valence is the anode. b. the most positive potential is the cathode in a practical galvanic series of metals, which of the following is represented? a. the potential between two different metals in the series is measured. b. the current is measured between two of the metals in the series. c. the electrolyte contains metal ions of that metal. d. the potential of metals in a common electrolyte d. the potential of metals in a common electrolyte the nernst equation calculates the potential of a metal in solutions of different metal ion concentrations a corrosion cell can form under which of the following conditions? a. a difference in temperature where teh higher temperature is the cathode. b. a difference in oxygen where the highest concentration of oxygen is at the anode. c. a difference in metals where the anode is at the most noble metal. d. a difference in salt concentration where the anode is at the highest ion concentration d. a difference in salt concentration where the anode is at the highest ion concentration when bare metal passes under a paved road surface, a. an oxygen concentration corrosion cell can develop with the metal under the pavement being the anode b. an oxygen concentration cell can develop with the metal outside the pavement being the anode c. a temperature corrosion cell can develop with the metal outside the pavement being the anode. d. a high salt concentration at the edge of the pavement with the metal under the pavement being the anode. a. an oxygen concentration corrosion cell can develop with the metal under the pavement being the anode an environment where cathodic protection is NOT effective is a. liquid pherically exposed surface d. steel in concrete c. atmospherically exposed surface the cathodic protection criteria for steel includes which of the following? I. a potential of -850 mVCSE or more negative with curent applied after IR drop is considered II. a polarized potential of -850mVCSE or more negative III. polarization of 100 mV or greater IV. a polarized potential of -790 mv AgAgCl or more negative all of the above when cathodic protection is applied to a corroding steel surface, it shifts the corrosion cell potential - a. no change in potential b. cathode more negative c. cathode more positive d. anode more positive b. cathode more negative cathodic protection polarizes a. the potential of the structure anode to the structure cathode potential b. the potential of the structure cathode to the structure anode potential. c. the potential of the structure cathode to the CP anode potential. d. the cp anode potential to the structure cathode potential. b. the potential of the structure cathode to the structure anode potential. the current requirement for cathodic protection of a structure will increase with a a. decrease in pH b. decrease in temperature c. decrease in oxygen d. decrease in velocity a. decrease in pH if lead, copper, steel, and aluminum are connected together in water, which will corrode the most? aluminum in a galvanic anode system, the driving voltage is due to the a. electrolyte itself to structure couple in the electrolyte ction to the structure d. anode backfill anode to structure couple in the electrolyte which is NOT a primary reaction at the anode? a. metal oxidation b. oxygen evolution ide evolution d. hydrogen evolution d. hydrogen evolution which of the following will decrease cathodic protection current requirements? a. increased pH b. increased oxygen c. increased temperature d. increased agitation a. increased pH a galvanic anode system is NOT normally suitable in which of the following conditions? a. when a small amount of current is required. high soil resisitivity localized protection interference mitigation. b. in high soil resistivity The purpose of the galvanic anode backfill is NOT to a. prevent passivation of the anode b. create uniform corrosion of the anode c. passivate the anode de a low resistivity environment around the anode. c. passivate the anode the elements of a galvanic cathodic protection system in soil includes which of the following? i. active material ii. noble structure iii. carbon backfill iv. wiring I, II, and IV only an impressed current system is NOT normally practical under which of the following conditions a. with very small current requirements b. for protection of poorly coated and bare structures c. in high soil resistivity d. inside water storage tanks a. with very small current requirements Rectifier components could include which of the following? I. Transformer II. Photovaltaic cells III. thermopile IV. silicon diodes I and IV only Which of the following DC power supplies are commonly used to charge batteries that in turn provide cathodic protection current? I. thermoelectric genorators II. solar III. wind-driven generator IV. saturable reactor II and III only A transformer will A. change AC to DC B. increase the DC voltage only C. decrease the ac voltage only D. increase or decrease the AC supply voltage D. increase or decrease the AC supply voltage If the primary AC voltage is 100 Volts AC, and there are 100 primary windings with 200 secondary windings, what is the the secondary voltage? A. 25 volts AC B. 50 Volts AC c. 100 volts AC d. 200 Volts AC d. 200 Volts AC (100 x 200) / 100 = 200 volts AC With a single diode installed in series with an AC voltage source the results will be a. half wave AC voltage b. halfwave DC voltage c. full wave AC voltage d. full wave DC voltage b. halfwave DC voltage full wave rectification can be achieved with I. a four diode bridge circuit. II. a center tap configuration. III. one silicon-controlled rectifier IV. two silicon-controlled rectifiers and two diodes in a bridge I, II, and IV only what is the purpose of a "free wheeling" diode? a. to prevent latching of the SCR b. to improve efficiency of the rectifier c. to convert AC to DC d. to increase or decrease the AC voltage a. to prevent latching of the SCR ??? the advantage of three phase rectifiers over single phase rectifiers is that they a. are more efficient b. have lower initial cost c. are easier to troubleshoot d. are easier to adjust a. are more efficient which DC power supply converts heat energy directly to electrical energy? a. transformer-rectifier c. thermoelectric generator -driven generator c. thermoelectric generator a constant potential rectifier provides a constant a. voltage output b. voltages between taps c. structure-to-electrolyte potential d. potential to the SCR c. structure-to-electrolyte potential a structure-to-electrolyte potential measures the potential difference between a. two different structures acting as electrodes b. the structure and a standard reference electrode c. the structure and the anode d. two different points on the structure b. the structure and a standard reference electrode a close interval potential survey is a test where structure-to-electrolyte potentials are measured a. at 1 to 5 meter spacing along a pipeline b. at 1 to 3 km spacing along a pipeline the quarter points around a large tank d. close to the DC power source a. at 1 to 5 meter spacing along a pipeline polarized potentials are measured a. when the rectifiers are ON b. just after the rectifiers are turned OFF c. after the rectifiers are left off for several days d. just after the rectifiers are turned ON b. just after the rectifiers are turned OFF polarization is determined by a. subtracting the ON from the instant OFF potential b. measuring the instant OFF potential c. subtracting the instant OFF from the Native (free corroding) potential acting the IR drop from the ON potential c. subtracting the instant OFF from the Native (free corroding) potential current pickup on a pipeline is indicated when a. the structure-to-electrolyte potential over the pipe is more electronegative than to each side. b. the structure-to-electrolyte potential over the pipe is more electropositive than to each side c. the two electrode method (side drain) shows the electrode over the pipe is more electropositive. ... What is the current in a 91 m (300 ft) span of 762 mm (30 in) pipe weighing 176.65 kg/m (118.7 lb/ft), if the voltage drop across that span is 0.62 mV? a. 0.850 A b. 1.176 A c. 2.802 A d. 2.585 A a. 0.850 A structure-to-electrolyte potentials can be used for which of the following purpose(s)? I. Confirm if a CP potential criterion is met II. Locate anodic areas on non-cp pipelines III. determine resistivity of the soil IV. locate stray current I, II, and IV only which of these would clearly indicate that a tank is isolated? a. a structure-to-electrolyte potential of -950 mvcse with the electrode at the pipe and a tank-to-electrolyte potential of -800mv cse with the electrode at the tank b. a structure-to-electrolyte potential of -950 mv cse with the electrode at the pipe and a tank-to-electrolyte potential of -940 mv cse with the electrode at the tank c.a structure-to-electrolyte potential of -950 mv cse with the electrode at the pipe and a tank-to-electrolyte potential of -800 mv cse with the electrode at the pipe d. a structure-to-electrolyte potential of -650 mv cse with the electrode at the pipe and a tank-to-electrolyte potential of -640 mv cse with the electrode at the tank c.a structure-to-electrolyte potential of -950 mv cse with the electrode at the pipe and a tank-to-electrolyte potential of -800 mv cse with the electrode at the pipe For steel in concrete what is the probability of corrosion at a potential of -370mvCSE? corrosion b.5% c.50% d.95% d.95% page 5-93 If current being impressed on to a structure is causing a potential gradient of 50 mv per meter (average_ and the reference electrode is 3 m from the structure, what is the potential being measured if the true potential at the structure is -800 mV? a. -150 mV b. -300 mV c. -950 mV d. +950 mV c. -950 mV (-800 - 150) = =950 with proper instrumentation, a dual soil coupon can be used to predict which of the following? I. The potential of the pipe surface at the location of the coupon II. the polarized potential of a coating holiday of a given size at the location III. The amount of polarization of a coating holiday of a given size at the location IV. The amount of CP current pick up on a coating holiday of a given size at the location. II, III, and IV only an electrolytic couple between a pipe and a casing A. shields CP current from the pipeline. B. causes a high current demand due to the casing. C. allows CP current to access the pipeline. D. causes corrosion on the outside of the casing C. allows CP current to access the pipeline With sufficient current applied to a pipeline which has an electrolytic couple to the casing, the potentials will A. shift electropositively on the outside of the casing B. shift electropositively on the pipe inside the casing C.shift electropositively on the inside of the casing D. will be the same on the pipe and the casing C.shift electropositively on the inside of the casing ????? A stray current is a current that A. goes back and forth B. goes in an unintended path C. goes only to a pipeline D. does not complete a circuit B. goes in an unintended path a mitigation control bond should be designed to I. carry the necessary current. II. restrict the current to that required to mitigate the problem. III. keep the current going in one direction if necessary IV. return the potential on the interfered with structure to its pre-interference state I, II, III, and IV a mitigation bond may cause more problems under which of the following conditions? I where the interfering structure bond point is more electropositive than the interfered with structure. II. where the interfering structure bond point is more electronegative than the interfered with structure III. where there are more than one, or changing, current discharge points IV. where the interfering structure bond point potential varies from being more electronegative to more electropositive than the interfered with structure. I, III, and IV only ????? AC voltages on pipelines do NOT result from A. resistive (conductive) coupling B. electrostatic (capacitive) coupling C. electromagnetic induction coupling D. thermodynamic coupling D. thermodynamic coupling on a cathodically protected pipeline, AC corrosion can be expected at which current densities? I. 20 mA/m^2 II. 10 A/m^2 III. 110 A/m^2 IV. 200 A/m^2 III and IV only i ac 20 A/m^2 ..... no corrosion 20 A/m^2 i ac 100 A/m^2 ... corrosion unpredictable i ac 100 A/m^2 .... corrosion expected The AC voltage-to-ground on a section of pipeline paralleling AND crossing a power line tends to be highest I. where the power line and pipeline cross II. point where the power line and pipeline seperate III. A gradient mat or a grid around above ground structures IV. A remote ground away from the parallel section I and II only Methods of lowering hazardous AC voltages include installing which of the following? I. grounds at the discontinuities between power line and pipeline II. A bond to the steel power line tower. III. a gradient mat or a grid around aboveground structures. IV. a remote ground away from the parallel section I and III only A polarization cell is used to A. polarize the pipeline. B. polarize the electrical ground C. provide DC coupling but block AC D. provide AC coupling but block DC D. provide AC coupling but block DC Tests for interference can be indicated by which of the following? I. Structure-to-electrolyte potential changes II. Changes in line current magnitude or direction III. Localized pitting in areas near or immediately adjacent to a foreign structure IV. breakdown of protective coatings in a localized area. I, II, III, and IV When AC voltage of 13 V is measured on a pipeline, what course of action should be taken? I Wait until next year and take an AC voltage to confirm it has not changed II. Contact the power company to determine what percent of load the power line is operating III. Advise other personnel that a near hazardous situation exists on the pipeline IV. Advise the owner or supervisor that an AC mitigation program should be investigated II, III, and IV The purpose of a gradient mat is to A. electrically ground the pipe to the earth to eliminate the AC voltage B. bring the voltage difference between the pipe and the earth close to 0 Vac C. provide cathodic protection to large structures such as tank bottoms D. to eliminate the earth gradient to obtain a true polarized potential B. bring the voltage difference between the pipe and the earth close to 0 Vac the corrosion rate of iron caused by current discharge is a. 15 pounds per ampere per year b. 20 pounds per ampere per year c. 20 pounds per ampere per month d. 40 pounds per ampere per year b. 20 pounds per ampere per year Ferrous 9.1 Kg/ A-yr or 20lbs / A-yr Copper 10.4 Kg/ A-yr or 23lbs / A-yr Lead 33.85 Kg/ A-yr (74.74lbs/ A-yr) Which of the following is NOT a source of dynamic stray current? A. Cathodic protection B. Mining equipment C. Transit systems D. Telluric current A. Cathodic Protection Stray current CANNOT be detected by A. structure-to-electrolyte potentials B. reference electrode to electrode measurements C. pipeline current span measurements D. Soil resistivity measurements D. Soil resistivity measurements Cathodic interference occurs A. in a voltage gradient that is positive to remote earth B. in a voltage gradient that is negative to remote earth C. at the cathode in a corrosion cell. D. at the structure's cathodic protection system. B. in a voltage gradient that is negative to remote earth an electronegative peak in potentials along a cathodically protected pipeline may be indicative of a. anodic interference b. cathodic interference c. shorted road casing d. current discharge a. anodic interference analysis of dynamic stray current does NOT typically include the evaluation of A. soil resistivity B. the interaction of voltages between different structures C. measuring of current on the structure D. correlation of current and voltages on different structures and A. soil resistivity With current (and direction) measured at adjacent spans on a pipeline, which condition indicates a current discharge (Location A is left of Location B A. Location A= 2.0 A (left) Location B= 1.0A (right) B. Location A= 2.0 A (right) Location B= 1.0 A (left) C. Location A= 1.0 A (left) Location B= 1.0 A (left) D. Location A = 1.0 A (right) Location B= 2.0 A (right) B. Location A= 2.0 A (right) Location B= 1.0 A (left) Recommended methods of mitigating cathodic interference from another cathodic protection system include which of the following? I. Drainage control bond II. cathodic protection III.Coating the current discharge area IV. Reduce source of stray current I, II, and IV ?? A complete cathodic protection system monitoring program consists of which of the following? A. Detailed survey only B. Routine readings between surveys only C. Detailed survey and routine readings between surveys D. Soil resistivity surveys C. Detailed survey and routine readings between surveys Proper operation of a rectifier can be confirmed by which of the following? I. DC current output II. DC voltage output III. tap setting IV. Potential at a control point all of the above ??? a short to bare structure will most likely cause which of the following? I. A decrease in the current output of the anode. II. An electropositive change in the pipe-to-electrolyte potential III. an increase in the current output of the anode IV. An electronegative change in the pipe-to-electrolyte potential.. II only Which of the following regulations require inspection of an interference control drainage bond? I. DOT 49 CFR 192 II. DOT 49 CFR 195 III. CSA Z662 IV. ISO 15589-1 All of the above ??? Reasons for keeping records include which of the following? I. Legal Defense II. Government regulations III. Historical references IV. Possible future ECDA assessment All of the above Which of the following items must be included in recording structure-to-electrolyte potentials on routine surveys? I. Value II. Units III. Polarity IV. Reference Electrode All of the above Which of the following is NOT necessary in establishing the integrity of an aging pipeline? A. Dig inspection data B. In-line inspection data C. Electrostatic voltages D. Leak History C. Electrostatic Voltages A job safety analysis allows a project to proceed when the I. hazards have been identified. II. risks have been identified. III. Preventative measures reduce the risk to an acceptable level. IV. risk increases I, II, and III only Which of the following is the maximum current passing through an average sized body that will allow the muscles to let it go? I. 4 mA II. 8 mA III. 120 mA IV. 480 mA II. 8 mA (9-25 mA can cause lack of muscular control, let-go current, that makes it impossible to release and in face it may cause the muscles to tighten.) It is safe to work behind the panel of a rectifier under which of the following conditions? I. When the rectifier breaker is off II. When the rectifier breaker is off and locked out III. When the outside DC cables are disconnected IV. when the outside AC disconnect is off and locked out. IV only A constant AC voltage-to-ground equal to or in excess of which of the following is considered to be hazardous? A. 5 voltsAC B. 15 VoltsAC C. 24 VoltsAC D. 40 VoltsAC B. 15 VoltsAC When measuring a structure-to-electrolyte potential, which of the following measurements should be taken first for safety? A. A soil resisitivity measurement B. The reference electrode contact resistance C. an AC voltage-to-ground D. The meter lead resistance C. an AC voltage-to-ground Hazardous materials include which of the following? I. Solvents II. Caustics III. Acids IV. Copper Sulfate all of the above Gases that either promote combustion or are flammable can be produced at the A. anode only B. protected structure only C. anode and structure D. neither the anode or structure C. anode and structure Before working on a project you must know which of the following? I. The possible hazards II. Where to go in case of emergency III. Contact people and telephone information IV. MSDS data for materials handled all of the above Personal protective equipment in plants includes which of the following? I. Hard hats II. Safety shoes or boots III. Fire retardant coveralls IV. Safety glasses all of the above Purpose of Transformer step up or step down AC supply voltage If a transformer has no losses, what is the secondary voltage of a transformer being supplied with 115 Vac that has 400 turns on the primary and 100 turns on the secondary windings Esecondary = (Eprimary x Secondary Turns) / Primary Turns E secondary= 115Vac x 100 / 400 = 28.75 Vac Three phase rectifiers available in Wye (3 diodes) or full-wave (6 diodes) with full-wave bridges. THREE-PHASE UNITS ARE MORE EFFICIENT THAN SINGLE-PHASE UNITS, BUT THE INITIAL INVESTMENT COSTS ARE HIGHER Electrode used in reinforced concrete manganese oxide electrode used in seawater and concrete Silver-silver chloride electrode used most frequently in lab experiments calomel which part of the structure polarizes first? the most cathodic site current requirement DIRECTLY proportional to surface area INVERSELY proportional to polarization Positive voltage terminal must ALWAYS be connected to the ANODE negative voltage terminal ALWAYS connected to STRUCTURE typical uses for Impressed current systems ... Kirchoff's voltage law The law states that the sum of the source voltages around any closed loop of a circuit is equal to the sum of the voltage drops across the resistances in that loop. Kirchoff's current law The law states that as much current flows away from a point as flows toward it. It is especially useful in analyzing parallel circuits and in tracing current flow in complex piping networks. Series circuit Current is the same everywhere Voltage drops may all be different depending on the value of each resistance, but the sum of the voltage drops (Et) must add up to the voltage of the source. The total resistance of a series circuit equals the sum of the individual resistances. parallel circuit current divides into a number of separate branches. each branch may have a different resistance;thus, the value of the current in each branch may be different. Voltage drop across each element or source in the circuit is the same. Voltage drop across each branch is the same and is equal to source voltage. Total current flowing into and out fo the junction point of the branches equals the sum of branch currents. total resistance is equal to the reciprocal of the sum of the reciprocals of the individual resistances. The total resistance is always less than the smallest resistance in the circuit. percent efficiency of rectifier percent efficiency = (DC Power out/AC power in) x 100 WATTS = Vdc x Idc AC Input power (3600 K N) / T where K = meter constant N= number of revolutions of the disk T= time in seconds of observation HMWPE insulation is not recommended for use in environments containing? chlorine, hydrochloric acid, or petroleum hydrocarbons. Four basic components of galvanic cp system anode, anode backfill, means of connecting anode to structure, and the structure Zinc anodes are commonly used in salt, brackish water aluminum alloy anodes are primarily used in ? seawater applications Remote Earth the point where the further distance from the anode produces no further change in voltage gradient cathodic protection systems for reinforced concrete use a distributed anode configuration consisting of a continuous anode on the concrete surface or closely spaced strips embedded in the concrete surface. galvanic anodes for atmospherically exposed reinforced concrete structures placed over the entire surface to distribute the current evenly single phase rectifiers have greater ripple than 3 phase silicon diodes more efficient than selenium diodes and they do not age PEARSON SURVEY used to detect holidays CURRENT FLOW CALCULATION FIND DIAMETER OF PIPE LOOK UP RESISTANCE OF THAT DIAMETER IN TABLE MULTIPLY RESISTANCE BY LENGTH (WATCH UNITS, FT OR M) THEN USING OHM'S LAW DIVIDE THE VOLTAGE BY THAT NUMBER. WATCH UNITS. NEED TO BE IN VOLTS AND METERS 1 OHM = 1,000,000 microohms 1 volt = 1000 millivolts DCVG (Direct Current Voltage Gradient) Surveys are used for what? detecting cathodic protection current pickup at coating holidays