galvanic anode การใช้

• ASTM International publishes standards on the composition and manufacturing of galvanic anodes.
• There are three main metals used as galvanic anodes, magnesium, aluminum and zinc.
• The galvanic anode continues to corrode, consuming the anode material until eventually it must be replaced.
• A simpler option is to use galvanic anodes, which are self-limiting and need no control.
• ASTM International publishes standards on the composition and manufacturing of galvanic anodes . [ 7 ] [ 8]
• For larger structures, or where electrolyte resistivity is high, galvanic anodes cannot economically deliver enough current to provide protection.
• Since ships are regularly removed from the water for inspections and maintenance, it is a simple task to replace the galvanic anodes.
• Galvanic anodes rely on the galvanic series potentials of the metals to drive cathodic protection current from the anode to the structure being protected.
• Smaller vessels, with non-metallic hulls, such as yachts, are equipped with galvanic anodes to protect areas such as outboard motors.
• In cases like this, aluminium or zinc galvanic anodes can be used to offset the potential difference between the aluminium hull and the steel fixture.
• The difference in potential between the two metals means that the galvanic anode corrodes, so that the anode material is consumed in preference to the structure.
• This effectively stops the oxidation reactions on the metal surface by transferring them to the galvanic anode, which will be sacrificed in favour of the structure under protection.
• Some ships may require specialist treatment, for example aluminium hulls with steel fixtures will create an electrochemical cell where the aluminium hull can act as a galvanic anode and corrosion is enhanced.
• Since the operation of a galvanic anode relies on the difference in electropotential between the anode and the cathode, practically any metal can be used to protect some other, providing there is a sufficient difference in potential.
• CP works by introducing another metal ( the galvanic anode ) with a much more anodic surface, so that all the current will flow from the introduced anode and the metal to be protected becomes cathodic in comparison to the anode.
• Many thousands of old underground tanks were replaced with newer tanks made of corrosion resistant materials ( such as fiberglass, steel clad with a thick FRP shell, and well-coated steel with galvanic anodes ) and others constructed as double walled tanks to form an interstice between two tank walls ( a tank within a tank ) which allowed for the detection of leaks from the inner or outer tank wall through monitoring of the interstice using vacuum, pressure or a liquid sensor probe.