ICCP CATHODIC PROTECTION PDF
MARELCO™ ICCP HULL PROTECTION SYSTEM (IMPRESSED CURRENT CATHODIC PROTECTION) For larger structures such as a Hull of a ship, the. Impressed Current Cathodic Protection (ICCP) of CORROSION Maritime, high quality protection against corrosion for maritime purposes. 2. Impressed Current Cathodic Protection (ICCP). ICCP is a more economical method of CP when underground pipelines are long or offshore equipment is too .
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To understand cathodic protection, you must first understand how corrosion is caused. For corrosion to occur, three things must be present:.
Two dissimilar metals 2. An potection water with any type of salt or salts dissolved in it 3. A metal conducting path between the dissimilar metals. The two dissimilar metals may be totally different alloys — such as steel and aluminum — but are more likely to be microscopic or macroscopic metallurgical differences on the surface of a single piece of steel.
In this case we will consider freely-corroding steel, which is non-uniform. If proteection above conditions exist, the following reaction takes place at the more active sites: The free electrons travel through the metal path to the less active sites, where the following reaction takes place: Recombinations of these ions at the active surface produce the following reaction, which yields the iron-corrosion product ferrous hydroxide: This reaction is more commonly described as ‘current flow through the water from the anode more active site to the cathode less active site.
Cathodic protection prevents corrosion by converting all of the anodic active sites on the metal surface to cathodic passive sites by supplying electrical current or free electrons from an alternate source.
Impressed Current Cathodic Protection
Usually this takes the form of galvanic anodeswhich are more active than steel. This practice is also referred to as a sacrificial system, since the galvanic anodes cathofic themselves to protect the structural steel or pipeline from corrosion. In the case of aluminum anodesthe reaction at the aluminum surface is: As long as the current free electrons arrives at the cathode steel faster than oxygen is arriving, no corrosion will occur.
Initially, current will be high because the difference in potential between the anode occp cathode are high, but as the potential difference decreases due to the effect of the current flow onto the cathode, the current gradually decreases due to polarization of the cathode. The circuit resistance includes both the water path and the metal path, which includes any cable in the circuit.
The dominant value here is the resistance of the anode to the seawater. For most applications, the metal resistance is so small compared to the water resistance that it can be ignored although this is not true for sleds or long pipelines protected from both ends.
In general, long, thin anodes have lower resistance than short, fat anodes. They will discharge more current but will not last as long. Therefore, a cathodic-protection designer must size the anodes so that they have the right shape and surface area to discharge enough current to protect the structure prohection enough weight to last the desired lifetime when discharging this current.
Due to proection high currents involved in many seawater systems, it is not uncommon to use impressed-current systems that use anodes of a type ICCP anodes that are not easily dissolved into metallic ions. This causes an alternative reaction: Current flow onto any metal will shift its normal potential in the negative direction.
History has shown that if steel receives enough current to shift the potential to – 0. Due kccp the nature of the films which form, the minimum All specifications subject to change without notice.
Offshore Icpc Protection For corrosion to occur, three things must be present: A metal conducting path between the dissimilar metals The two dissimilar metals may be totally different alloys — such as steel and aluminum — but are more likely to be microscopic or macroscopic cathoduc differences on the surface of a single piece of steel. Sacrificial anode system in seawater. Impressed-current cathodic-protection system in seawater.
Protected vs unprotected structures as verified by cathodic-protection potential.