Cathodic Protection System

K. C. LTD. MARINE IMPRESSED CURRENT CATHODIC PROTECTION SYSTEM ICCP DOCUMENT REV(E) : 14/04/06 NOTES : a) Do not attempt to service or readjust the system operating levels without first reading and understanding this Manual. b) The system operates at low d. c. voltage levels and may be severely damaged by high voltage test equipment such as a 500V Megger. Read the relevant section in this manual before carrying out any tests. ) There is no need of protective current as far as ship is well enclosed by a good hull coating (newbuildings or just repaired ships) or the temporary sacrificial anodes around ship’s bow and stern hull area are still alive, which means our system dissipates no current under fully automatic control realizing ship is well protected from corrosion. Then you may see protective current when ship’s hull coating gets thinner and thinner or partly damaged. d) Should any information be required which is not covered by this manual, please contact K. C. LTD. immediately. Address on cover) CAUTION Customers are recommended for the purchase of genuine parts from us. Imitated parts make the system get fatally damaged. -4“C:ManualICCPICCP Document. doc K. C. LTD. 1. 0 INTRODUCTION: 1. 0. 1 PRINCIPLES OF CORROSION AND CATHODIC PROTECTION: ICCP DOCUMENT REV(E) : 14/04/06 Metallic corrosion is an electro-chemical reaction in which the metal combines with a non metal, such as oxygen, to form a metal oxide or other compound. This depends upon the nature of the environment. Different metals have different tendencies to corrode, activity or potential.

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These potentials can be tabulated and form the electro-chemical series. A more practical approach is the determination of the tendency of certain metals to corrode in a particular electrolyte, such as sea water. This is termed the galvanic series of which the following table is an abridged form. Active or Anodic Magnesium Zinc Mild Steel Wrought Iron Cast Iron Ni-Resist 18. 8. 3% Molybdenum SS, Type 316 (Active) Lead Tin Manganese Bronze Naval Brass Aluminium Bronze Copper 70 Copper 30 Nickel Nickel (Passive) Monel, 70% Nickel-30% Copper 18. 8. % Molybdenum SS, Type 316 (Passive) Noble or Cathodic Note Some metals and alloys have two positions in the series, marked Active and Passive; the active position is equivalent to the position if corrosion is occurring and approaches the electro-chemical series position for the material. The passive position relates to a non-corroding situation where the material is protected by a self forming surface film. For example, type 316 stainless steel in sea water is more likely to be passive than type 304 and is therefore generally preferred for immersed marine applications. 5“C:ManualICCPICCP Document. doc K. C. LTD. ICCP DOCUMENT REV(E) : 14/04/06 If two metals are placed in an electrolyte (e. g. sea water or damp soil) and are in direct electrical contact, a current will pass through the electrolyte from the more active metal onto the least active metal. The least active metal does not corrode and is termed the cathode. The more active metal, the anode, passes into solution and the flow of electrical current increases. This is a metal ion and electron transfer process i. e. , it corrodes. This simple cell may be represented as:

Figure 1. 1 – Simple Corrosion Cell The anodic and cathodic areas in a corrosion cell may be due to the electrical contact of two dissimilar metals, galvanic corrosion. Anodic and cathodic areas may be formed on a single metal surface as micro-cells for instance by rain drops on uncoated steel. Alternatively, they may be close but discrete cells found when accelerated corrosion occurs at uncoated anodic areas on a generally coated cathodic structure. In addition there are long line type cells that occur on pipelines that pass through aggressive low resistivity solis.

These sections form anodic areas and corrode in preference to cathodic areas in less aggressive higher resistivity soils. Large currents can occur at small anodic areas and lead to rapid corrosion of marine structures such as ship’s internal tanks, external hull plates, sheet steel piling in harbours and tubular structures common in jetties and petrochemical drilling and production platforms. Cathodic Protection is a system of preventing corrosion by forcing all surfaces of a structure to be cathodes by providing external anodes.

As described above, a galvanic corrosion cell occurs when dissimilar metals are in contact with each other within an electrolyte. Care should be taken in the construction of structures that will be buried or immersed in an electrolyte to ensure a galvanic cell is not created. -6“C:ManualICCPICCP Document. doc K. C. LTD. Typical example of galvanic cells are: a) ICCP DOCUMENT REV(E) : 14/04/06 Steel or cast iron water boxes in contact with non ferrous (often copper based) tube plates in condenser water boxes in ships or generating plant. Rapid corrosion of the ferrous water box occurs close to the tube plate.

Brass or bronze valves fitted to immersed steel buoyancy tanks or flooding chambers on marine petrochemical structures. Accelerated corrosion of the steel occurs near the valve. The connection of steel pipes into an otherwise cast iron system. Accelerated corrosion of the steel occurs near the cast iron sections. b) c) Sacrificial anode cathodic protection achieves corrosion prevention on a particular structure or component by forming galvanic cell where an additional anode of zinc, magnesium or aluminium corrodes in preference to the structure.

The galvanic corrosion current (see simple cell before) available from this anode / electrolyte / structure combination should be sufficient to overcome the local surface corrosion currents on the structure until no current flows from anodic areas of the structure i. e the structure is entirely cathodic or under complete cathodic protection. The potential, or measure of activity, between the structure and the electrolyte is a relatively easily measured indication of whether the structure is anodic or cathodic.

For steel under normal non anaerobic conditions it can be shown theoretically, and is accepted practically, that a steel / electrolyte potential more negative than -0. 85 volts measured against a standard copper / copper sulphate ref cell indicates that cathodic protection is achieved. This is equivalent to -0. 80 volts measured against silver / silver chloride ref cell and + 0. 24 volts against a zinc ref cell as indicated in figure 1. 3. SACRIFICIAL ANODE CATHODIC PROTECTION: As indicated previously, a metal can be made cathodic by electrically connecting it to a more anodic metal within the electrolyte.

The most commonly used anodic metals are alloys of aluminium, zinc and magnesium. Anodes of these metals corrode preferentialy, the corrosion current of the anode achieving cathodic protection of the structure to which they are connected. The anodes deteriorate as an essential part of their essential part of their function and they are therefore termed sacrificial. -7“C:ManualICCPICCP Document. doc K. C. LTD. 2. 0 GENERAL DESCRIPTIONS: 2. 1. 1 IMPRESSED CURRENT CATHODIC PROTECTION: ICCP DOCUMENT REV(E) : 14/04/06

A metal also can be made cathodic by electrically connecting it to another metallic component in the same electrolyte through a source of direct electric current and directing the current flow to occur off the surface of added metallic component (anode), into the electrolyte and onto the metal (cathode). This can easily be visualised by reference to the simple cell and assuming yet another ref cell with a power source is introduced and that the current flow from this ref cell is sufficient to overcome the natural corrosion current.

Because an external current source is employed, this type of protection is termed ‘IMPRESSED CURRENT CATHODIC PROTECTION’. Figure 1. 2 – Cathodic Protection Applied to a Simple Corrosion Cell A source of direct current is required, this is generally obtained from mains power units that contain a transformer and rectifier. The magnitude of this current may be automatically controlled in response to a continuous monitor of the cathode / electrolyte potential or may be manually controlled after intermittent measurement.

The impressed current anode material is ideally non-consumed by the passage of current from it into the electrolyte, in practice the materials used are a compromise between this ideal and the cost and physical properties of available materials. Impressed current anodes are made from graphite, silicon iron, lead alloys some with platinum dielectrodes, platinised titanium or more exotic combinations such as platinum clad niobium. The selection of the correct anode material is critical in the formulation of an effective and economic cathodic protection scheme. -8“C:ManualICCPICCP Document. doc K. C. LTD.

ICCP DOCUMENT REV(E) : 14/04/06 Generally, for a given current demand, less impressed current anodes than sacrificial anodes are required for protection, as high anode currents are feasible. Impressed current systems of cathodic protection are more sophisticated in design than sacrificial systems. Figure 1. 3 – Comparison of Reference Electrodes & Interpretation 2. 2. 0 MARINE IMPRESSED CURRENT SYSTEM: The Marine Impressed Current System comprises the following components, as illustrated in figure 1. 4. 2. 2. 1 IMPRESSED CURRENT ANODES The function of the anode is to conduct the d. c. protective current into the sea water.

Anodes have been designed to perform this function whilst maintaining a low electrical resistance contact with the sea water. Standard surface mounted anodes are available with from 50 to 300 Ampere ratings. For forward mounted systems and for special applications 50, 75, 100 and 175 Ampere recessed anodes are available. Materials now used by Anodes have now gone beyond lead alloy with specialist coated titanium based Anodes now available. All anode designs utilise a tough, chlorine resistant, but slightly flexible plastic carrier. -9“C:ManualICCPICCP Document. doc K. C. LTD. ICCP DOCUMENT REV(E) : 14/04/06

The use of a 24 volt system reduces the number and length of the anodes from that required with a 12 volt system. The increased anode / sea water resistance resulting from this decrease in anode size is overcome by the additional voltage. Recommended cable sizes for various run lengths are tabulated in section 3. 5. 4 The potential of the hull steel to the sea water is unaffected by this increase in driving voltage, as the resistive effects are local to the anode and the hull / sea potential is a function of the current flow, the sea water and the coating condition, not the driving voltage.

The electrical connections to the active surface are made at the back of the anode and are fully encapsulated and protected by the hull penetration. Recessed anodes of essentially similar construction are provided for bow section applications. All hull penetrations are provided with substantial doubler plates and cofferdams. The penetrations themselves are made watertight with heavy duty packing glands, the cofferdams are full sealed and provided with watertight cable glands, all conforming to the requirements of Classifications Societies. 2. 2. IMPRESSED CURRENT REFERENCE ELECTRODE The high purity, high stability, zinc ref cell are designed to give a stable reference against which the hull / sea potentials can be measured and a small current flow that is used in the closed loop circuit to maintain the preset levels of protection. The construction and the quantity of zinc employed within the electrodes are such that a minimum life of ten years is available without maintenance or replacement. The minimum number of ref cell per power supply is one although normally two will be fitted. Ideally, these should be located a minimum of 7. metres distant from the anodes. In the case of a stern only installation with the anodes more than 200 metres from the bows, one ref cell may be located in the bows. A novel feature of the closed circuit is that additional reference cells may be placed at areas that may be susceptible to over-protection such as adjacent to the anode dielectric shields. These additional reference cells provide a permanent check, thus preventing any coating damage due to over-protection if conditions of operation change from those anticipated. This feature is offered as an optional extra to the standard schemes. 10 “C:ManualICCPICCP Document. doc K. C. LTD. ICCP DOCUMENT REV(E) : 14/04/06 All hull penetrations are provided with substantial cofferdams. The penetrations themselves are made watertight with heavy duty packing glands. The cofferdams are fully sealed and provided with watertight cable glands. 2. 2. 3 BONDING To enable the rudder to receive protection it is provided with a dedicated electrical bond in the form of a flexible cable from the top of the rudder stock to the main ship structure. In the same way any stabilisers are bonded to allow protective current to these surfaces.

To allow protection of the bare propeller and any exposed shafting and to prevent electrical arcing between shaft and bearings the propeller shaft is fitted with a slipring assembly as optional items. A set of brushes provide the completion of a low resistance path to allow current to flow to the propeller blades along the shaft and back to the hull. The slipring track is silver plated as standard and in addition silver graphite brushes are used to minimize contact resistance. – 11 “C:ManualICCPICCP Document. doc K. C. LTD. 3. 0 3. 0. 1 ICCP DOCUMENT REV(E) : 14/04/06

POWER SUPPLY UNIT OPERATING INSTRUCTIONS When main power is ON the LCD works as per following steps. `Each step is shown on LCD for approximately 10 seconds. 1) The phase and frequency of input AC source, system capacity (OOOA) and type of ref. cell are displayed. Company logo of K. C. Ltd. is displayed. 2) 3) Company name (K. C. LTD. ) is displayed. 4) System is ready to work. 5) AUTO on OP MODE (Operation Mode) is displayed according to initial setting. System should be kept on AUTO. 6) Otherwise Press ESC KEY and select OP MODE by turning ESC KEY and then pressing ENTER KEY.

Then select AUTO by turning ESC KEY and pressing ENTER KEY. 7) 8) Then the LCD displays OP MODE and press ESC KEY. 9) YES / NO to save AUTO is displayed and then select YES by pressing ENTER KEY. ? Please keep system on AUTO. – 12 “C:ManualICCPICCP Document. doc K. C. LTD. 3. 0. 2 Details of Controller ICCP DOCUMENT REV(E) : 14/04/06 3. 0. 3 MODE Description Display on LCD Description OP MODE (Operation Mode) – OP MODE SELECTION OP MODE returns by pressing ESC KEY in AUTO or MANUAL. OP MODE is selected by turning ESC KEY and accessed in AUTO or MANUAL by pressing ENTER KEY. AUTO or MANUAL on OP MODE The display indicates OP MODE to access AUTO or MANUAL. AUTO or MANUAL is selected by turning ESC KEY and pressing ENTER KEY. – AUTO on OP MODE The display indicates the values on percentage of total system capacity, ref. cell, output current in Ampere and voltage. Each ref. cell value is scrolled one by one and also selected by pressing ENTER KEY. All readings vary automatically on ref. cell value. System should be left on AUTO. – MANUAL on OP MODE The display indicates the set value on percentage of total system capacity, ref. ell, output current in Ampere and voltage. Each ref. cell value is scrolled one by one and also selected by pressing ENTER KEY. All readings vary on the percentage set manually by user. The percentage of total system capacity is increased by turning ENTER KEY clockwise and decreased by turning anti clockwise. – 13 “C:ManualICCPICCP Document. doc K. C. LTD. SET MODE – SET MODE SELECTION ICCP DOCUMENT REV(E) : 14/04/06 SET MODE returns by pressing ESC KEY in AUTO or MANUAL. The SET MODE is selected by turning ESC KEY and accessed in FAULT SET or UNIT SET by pressing ENTER KEY. FAULT SET or UNIT SET on SET MODE The display indicates system setting to access FAULT SET or UNIT SET. FAULT SET or UNIT SET is selected by turning ESC KEY and PASSWORD is accessed by pressing ENTER KEY. – PASSWORD REQUEST This mode provides access to the service functions provided in the system setting. Access to this mode is only available from the permission of maker. Press ESC KEY to escape this mode. – 14 “C:ManualICCPICCP Document. doc K. C. LTD. 3. 1 3. 1. 1 ICCP DOCUMENT REV(E) : 14/04/06 CHANGING OPERATION MODE There are two MENU on operation mode. Thus ; ) AUTO In this mode the output current from the system is varied to maintain optimum ref. cell value. The display indicates the values on percentage of total system capacity, ref. cell, output current in Ampere and voltage. Each ref. cell value is scrolled one by one and also selected by pressing ENTER KEY. All readings vary automatically on ref. cell value. System should be left on AUTO. 2) MANUAL In this mode the output current from the system is manually set by user and maintained at a constant level. The display indicates the set value on percentage of total system capacity, ref. ell, output current in Ampere and voltage. Each ref. cell value is scrolled one by one and also selected by pressing ENTER KEY. All readings vary on the percentage set manually by user. The percentage of total system capacity is increased by turning ENTER KEY clockwise and decreased by turning anti clockwise. 1 0 OR 2 0 3 0 4 0 5 0 – 15 “C:ManualICCPICCP Document. doc K. C. LTD. 3. 1. 2 ICCP DOCUMENT REV(E) : 14/04/06 The system is controlled by using two keys on controller with the information showed on the 4 line display. To change AUTO or MANUAL take following step referring to figure 2-1 and 2-2. ) Upon main power on the LCD displays ? or ? in figure 2-1. 2) By pressing ESC KEY the LCD displays ? in figure 2-1. 3) By pressing ESC KEY in display ? in figure 2-1 the LCD displays ? or ? back. By pressing ENTER KEY in display ? in figure 2-1 the LCD displays ? or ? in figure 2-1. 4) The display ? in figure 2-1 indicates AUTO and ? indicates MANUAL. By pressing ENTER KEY in display ? in figure 2-1 the LCD displays ? back after setting AUTO which should be kept unless otherwise specially notified. 5) By pressing ENTER KEY in display ? in figure 2-1 the LCD displays ? back after setting MANUAL. ) By pressing ESC KEY in display ? in figure 2-1 the LCD displays YES / NO to save as per in figure 2-2. 7) By pressing ENTER KEY in display ? in figure 2-2 the display approaches ? saving any change. After saving any change the LCD displays ? or ? in figure 2-1. 8) By pressing ENTER KEY in display ? in figure 2-2 the display approaches ? and displays ? or ? in figure 2-1. a 0 c 0 b 0 d 0 – 16 “C:ManualICCPICCP Document. doc K. C. LTD. 3. 2 FAULT STATUS This mode as shown in figure 3-1 displays the status of fault. In case external alarm is provided for vessel’s alarm system the alarm triggers.

ICCP DOCUMENT REV(E) : 14/04/06 Description No message and alarm triggers in case power supply fails. CELL 1 UNDER PROTECTION No. 1 ref. cell reads UNDER PROTECTION of system. CELL 2 UNDER PROTECTION No. 2 ref. cell reads UNDER PROTECTION of system. CELL 1 OVER PROTECTION No. 1 ref. cell reads OVER PROTECTION of system. CELL 2 OVER PROTECTION No. 2 ref. cell reads OVER PROTECTION of system. ANODE OPEN STATUS Anode cable is open circuit. – 17 “C:ManualICCPICCP Document. doc K. C. LTD. ANODE SHORT STATUS ICCP DOCUMENT REV(E) : 14/04/06 Anode cable is short circuit.

PCB BOARD PROBLEM NEED A/S FROM MAKER Control PCB gets faulty. Kindly contact K. C. Ltd. for the remedy in case above fault status occurs. Address : 1589-6, Songjung-dong, Kangsu-ku, Busan 618-818, Korea Tel : +82 51 831 7720 Fax : +82 51 831 7726 E-mail : [email protected] com – 18 “C:ManualICCPICCP Document. doc K. C. LTD. 4. 0 ROUTINE OPERATING PROCEDURE: ICCP DOCUMENT REV(E) : 14/04/06 The K. C. LTD.. Marine Impressed Current System is completely automatic with little maintenance required and will normally require no adjustments during routine operation of the vessel.

However, careful attention on a routine basis should be given to the following points, by the ships staff to ensure that the system is kept operating at maximum efficiency at all times. 4. 0. 1 EVERY DAY: Check that the LCD of the Power Supply unit display is illuminated. Record the out put Current & Voltage and the ref cell reading on the log sheets provided. 4. 0. 2 EVERY WEEK: Once weekly the slipring should be checked for cleanliness, for wear on the brushes and to confirm that the brushes move freely in their holders and are held firmly onto the slipring by the brush holder spring.

Check the rudder stock bonding cable for any fraying of the conductor at the connection points. 4. 0. 3 EVERY MONTH: Each log sheet has space for a complete month after which the copies should be returned to K. C. LTD. for scrutiny and comment. 4. 0. 4 EVERY 3 MONTHS: Every 3 months switch off the equipment isolate the power externally to the unit remove the covers and inspect the power supply unit internally for signs of loose wires or other visual defects. The power supply unit is, under normal operation, fan cooled, and depends on free circulation of cooling air through the vents to maintain safe working temperature of components.

Check that the ventilation grilles in the sides and top are not obstructed in anyway. Clean any dust and dirt from the unit paying particular attention to the cooling fan. Replace all covers provide power and operate the mains switch to the On position and shut the front door. – 19 “C:ManualICCPICCP Document. doc K. C. LTD. 4. 0. 5 30 DAYS PRIOR TO DRY-DOCKING : ICCP DOCUMENT REV(E) : 14/04/06 One month before the dry docking ensure that daily log sheets have been maintained and forwarded to K. C. LTD. for assessment with information that dry docking is expected.

This will ensure that any necessary spares can be despatched in good time. Continue to log the system reading up to the time the vessel enters the dry dock. It is advised that an Engineer from K. C. LTD. be in attendance during drydocking to check and service the System. 4. 0. 6 FRESH WATER OPERATION: At times when the vessel enters a river estuary where the water may be fresh or brackish the effect will be to limit the spread of current from the anodes because of the much higher electrical resistivity of water.

Normally this will cause the automatic control to increase the transformer rectifier output voltage to the maximum but this will be accompanied by a very low level current and the reference ref cell potentials may indicate under protection. However, this has been taken care of by our computer and is explained in a seperate paragraph in 5. 1 The system will return the hull to the optimum protective level as soon as the vessel returns to the seawater. During ship’s sailing in fresh water or blackish water it’s recommended to cut off the system since the high system voltage under zero output current can reduce anode life significantly. 20 “C:ManualICCPICCP Document. doc K. C. LTD. 5. 0 SERVICING AND FAULT FINDING: 5. 0. 1 5. 0. 2 RECOGNITION OF A PROBLEM: ICCP DOCUMENT REV(E) : 14/04/06 From consideration of section 1 it will be appreciated that the D. C. output current of the system is the factor that provides the Cathodic Protection of the hull. In a correctly functioning system the level of current output gives an indication of the state of the paint system. The voltage or potential reading on the reference electrode cell circuit is the voltage of the hull with respect to the reference electrode cell.

Application of protective current changes this potential in a negative direction as indicated in figure 1. 3 from a level of +0. 20 volt for optimum protection. This example gives levels will respect to zinc ref cells. The D. C. output voltage is the driving potential that produces the protective current. The standard K. C. LTD. Marine Impressed Current System has a maximum voltage output of 24V DC but this is automatically regulated according to the current requirement. Bearing the above points is mind, it is clearly important to maintain the daily log and return the copies to K.

C. LTD. for scrutiny at the end of each month. Thus any abnormality in the readings will be noted and diagnosed and recommendations can be forwarded for action to be taken without undue delay. In reviewing the daily log sheets it is necessary first to check that the ref cells are within the range of protection and then to asses the output current and volts for variations in the level of protection applied. Do not megger, or high voltage test this equipment. The DC and control circuits are low voltage only and will be seriously damaged if high voltage test equipment is used.

To check insulation of any cables outside the Power Supply Unit disconnect them at both ends. If the LCD display is not illuminated then first check the mains supply to the cabinet and that the system is switched on. If no fault can be found then report conditions to K. C. LTD. 5. 0. 3 5. 0. 4 5. 0. 5 5. 0. 6 5. 0. 7 5. 0. 8 5. 0. 9 When any of the alarm conditions are found to be displayed contact K. C. LTD. giving full details of the alarm. – 21 “C:ManualICCPICCP Document. doc K. C. LTD. 5. VESSEL IN FRESH WATER: ICCP DOCUMENT REV(E) : 14/04/06 ICCP systems have experienced problem in the past when the vessel has to enter a harbour or estuary where the water is either fresh or brackish. The computer controller has been programmed to identify this situation by analysing the voltage reading, the amperage reading and the ref cell inputs. In fresh water the amperage goes to zero, the ref cell readings go high and the voltage tends to go to maximum to compensate. – 22 “C:ManualICCPICCP Document. doc