Cathodic Protection Solutions:Timna offers Cathodic Protection solution to companies and utility firms plagued by problems of corrosion of steel pipelines, tanks and structures. This service is extended to customers in desalination, petroleum drilling and mining industries. Cathodic protection systems are most commonly used to protect steel, water/fuel pipelines and storage tanks; steel pier piles, ships, offshore oil platforms and onshore oil well casings.
Timna offers Impressed Current Cathodic Protection (ICCP) solution. This consists of connecting an external anode to the metal to be protected and the passing of an electric current so that all areas of the metal become cathodic and, therefore, do not corrode. In electro-chemical terms, the electrical potential between the metal and the electrolyte solution, which is in contact, is lowered to a value at which corroding anodic reactions are silent and only cathodic reactions can take place.
Timna offers the entire range of services from consultancy and design to installation and commissioning of Cathodic protection systems.
- Soil Resistivity Testing
- Cathodic Protection Monitoring
- Close Interval Potential Surveys (CIPS)
- Direct Current Voltage Gradient Survey
- Current Drainage Survey
- AC Interference Testing
Timna has successfully executed several Cathodic protection projects mostly along the red sea coat of Saudi Arabia. Many of these executions were for the highly corrosive sea water intakes areas of desalination plants. These areas are sometimes difficult and often dangerous to operate in and over the years, Timna has developed expertise is tackling even such complex environments.
cathodic protection rectifier connected to a pipeline
Impressed Current CP
Impressed Current Cathodic Protection (ICCP) systems use anodes connected to a DC power source (a cathodic protection rectifier). Anodes for ICCP systems are tubular and solid rod shapes or continuous ribbons of various specialized materials. These include high silicon cast iron, graphite, mixed metal oxide, platinum and niobium coated wire and others.
A typical ICCP system for a pipeline would include an AC powered rectifier with a maximum rated DC output of between 10 and 50 amperes and 50 volts. The positive DC output terminal is connected via cables to the array of anodes buried in the ground (the anode groundbed). For many applications the anodes are installed in a 60 m (200 foot) deep, 25 cm (10-inch) diameter vertical hole and backfilled with conductive coke (a material that improves the performance and life of the anodes). A cable rated for the expected current output connects the negative terminal of the rectifier to the pipeline. The operating output of the rectifier is adjusted to the optimum level by a CP expert after conducting various tests including measurements of electrochemical potential.
Telephone wiring uses a form of cathodic protection. A circuit consists of a pair of wires, with forty-eight volts across them when the line is idle. The more positive wire is grounded, so that the wires are at 0 V and -48 V with respect to earth ground. The 0 V wire is at the same potential as the surrounding earth, so it corrodes no faster or slower than if it were not connected electrically. The -48 V wire is cathodically protected. This means that in the event of minor damage to the insulation on a buried cable, both copper conductors will be unaffected, and unless the two wires short together, service will not be interrupted.
If instead the polarity were switched, so that the wires were at 0 V and +48 V with respect to the surrounding earth, then the 0 V wire would be unaffected as before, but the +48 V wire would quickly be destroyed if it came into contact with wet earth. The electrochemical action would plate metal off the +48 V wire, reducing its thickness to the point that it would eventually break, interrupting telephone service. This choice of polarity was not accidental; corrosion problems in some of the earliest telegraphy systems pointed the way. |
