CATHODIC PROTECTION SERVICESES
 

Cathodic protection is defined as a reduction or elimination of corrosion by making a metal a cathode by means
of an impressed d-c current or attachment to a sacrificial anodes.

The basic cathodic protection solution to a galvanic corrosion problem is to introduce an anode in a suitable alloy
of aluminium, zinc or magnesium anodes which will suffer corrosion and so be "Sacrificed" in protecting the cathode-
Steel Plate. This approach is used in Sacrifical System.

As an alternative solution, the protective current needed to make the structure fully cathodic may be obtained by applying low voltage DC derived from the normal AC main supply. This is achieved by transformer / rectifer which
supply DC to specially design "insert" anodes which will disspate large current without themselves suffering
significant wastage. This approch is used in Impressed Current System.

CPS adopts the state of the art technology in our own manufacturing plant with assurance quality control by
utilising Optical Emission Spectrometer, it ensures that the anodes produced are in accordance with CPS required
chemical compositions. The current foundry is capable of producing 2500 tons of zinc anodes & 800 tons of
aluminium anodes.

  
  CORROSION -- How It Occurs  
  Steel and other ferrous metals are refined from stable compound called ores by a process requiring a large input of
energy. These key materials are used in construction of shiphulls, pipelines, storage tanks, industrial plants, decks,
piers and offshore platforms which will come in contact with oil, seawater and other conductive electrolytes. When
This occurs, the refined metal have a marked tendency to release the stored energy by combining with oxygen or
various chemical present in the electrolyte and return to their original stable form of iron oxide or rust.

This process is called corrosion. The actual corrosion process is electrochemical and quite complex.

When two dissinilar metal are connected in an electrolyte, such as sea water ,a corrosion cell is formed where
ore metal becomes the anode and suffers corrosion while the other becomes the cathode and is preserved.

Anodic and cathodic areas exist on the surface of all steel structure due to slight variations in material composition,
local stress, differences in coating condition and availability of oxygen. For example, a ship is built of a considerable
tonnage of steel Manufactured from numerous "Cast" possibly from several / producers, so surface of the steel
structure of ship will encompass a host of corrosion cells.

These corrosion cells can be insulated and suppressed by the application of coatings. Undoubtedly, modern marine
or industrial coating are of extremely high standard, but complete corrosion prevention cannot be achieved. Such
defficiency can be due to a host of reasons like inadequate surface preparation, incorrect application techniques or even mechanical damage in service from contact with floating objects, abrasion by tugs, jetties and the vessel's
own anchor cable.

When an imperfect coating exists, corrosion will take the form of accelerated pitting at the location of the bare spot.
If left unchecked, such process will cause leaks or structural deterioration necessitating repair or replacement of the
entire structure. The end result increases downtime, loss of product, hazardous working conditions and possible
product contaminations and damage to the environment.		  
  Basic Principles Of Cathodic Protection  
  Cathodic protection is defined as a reduction or elimination of corrosion by making a metal a cathode by means of
an impressed d-c current or attachment to a sacrifiical anode.

The principle of cathodic protection involves the introduction into the electrical circuit of a metal that is more
electro-nrgative than the existing anodic and cathodic areas.

This additional metal becomes the anode and will corrode and in so doing provides current to the metal it is
protecting, thereby overcoming the local anodic areas and making them cathodic. The classic cathodic protection
solution to a galvanic corrosion problem is to introduce an anode in a suitable alloy of magnesium, aluminum or
zinc which will suffer corrosion and so be "Sacrificed" in protecting the cathode. This approach is used in
Sacrificial System.

As an alternative solution, the protection current needed to make the structure fully cathodic may be obtained by
applying low voltage DC derived from the normal AC mains supply. This is achieved by transformer / rectifiers which
supply DC to specially design "intert" anodes which will dissipate large currents without themselves suffering
significant wastage. This approach is used in Impressed Current System.