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Cathodic protection (CP; / k æ ˈ θ ɒ d ɪ k / ⓘ) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. [1] A simple method of protection connects the metal to be protected to a more easily corroded "sacrificial metal" to act as the anode. The sacrificial metal then corrodes ...
In brief, corrosion is a chemical reaction occurring by an electrochemical mechanism (a redox reaction). [1] During corrosion of iron or steel there are two reactions, oxidation (equation 1), where electrons leave the metal (and the metal dissolves, i.e. actual loss of metal results) and reduction, where the electrons are used to convert oxygen and water to hydroxide ions (equation 2): [2]
Galvanic corrosion (also called bimetallic corrosion or dissimilar metal corrosion) is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte.
A simple test for measuring corrosion is the weight loss method. [15] The method involves exposing a clean weighed piece of the metal or alloy to the corrosive environment for a specified time followed by cleaning to remove corrosion products and weighing the piece to determine the loss of weight. The rate of corrosion (R) is calculated as
Corrosion monitoring is the use of a corrator (corrosion meter) or set of methods [1] and equipment to provide offline or online information about corrosion rate expressed in mpy (mill per year). [ 2 ] - for better care and to take or improve preventive measures to combat and protect against corrosion .
A sacrificial metal is a metal used as a sacrificial anode in cathodic protection that corrodes to prevent a primary metal from corrosion or rusting. [1] It may also be used for galvanization. Equation
Cathodic Protection: Cathodic protection is a technique used to protect metals from corrosion by applying a small electrical current to the metal surface. This technique can also help prevent SCC by reducing the corrosion potential of the metal. [7] Environmental Controls: Controlling the environment around the metal can help prevent SCC.
The unshaded bars indicate the location on the chart of those steels when in acidic/stagnant water ( like in the bilge ), where crevice-corrosion happens. Notice how the *same* steel has much different galvanic-series location, depending on the electrolyte it's in, making prevention of corrosion .. more difficult.