Corrosion - Pitting

Pitting corrosion, or pitting is a form of extremely localilzed corrosion that leads to the creation of small holes in the metal.  The driving power for pitting corrosion is the infection of a small area, which becomes corrosive, leading to very localized galvanic corrosion.  The corrosion penetrates the mass of the metal.  The mechanism of pitting corrosion is probably the same as crevice corrosion.  Pitting corrosion is particularly insidious.  The attack is in the form of highly localized holes that can penetrate inwards extremely rapidly, while the rest of the surface rermains intact.  A component can be perforated in a few days with no appreciable loss in weight on the structure as a whole.

 

Pitting corrosion, usually of the water tubes of the heater or radiator core, is the principle form of corrosion of aluminium radiators and occurs when, for a variety of reasons, the coolant is prevented from protecting the cooling system.  This most often occurs as tiny pinholes beneath deposits of sludge and sediment.

Unfortunately, these deposits don't just occur because the vehicle overheated on a country road and the owner was forced to fill the cooling system from a muddy creek or dam.  Over time, and if denied the regular maintenance described by the manufacturer, the very product that protects the system can also bring about its failure.

 


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