Visual inspection of line hardware is generally difficult due to these items being elevated. However,in most cases corrosion can be identified by means of binoculars in the form of rust staining,black deposits and discoloration.
The forms of corrosion most often encountered on line hardware are general pitting,crevice and galvanic corrosion . These components would mostly be hot galvanised of electroplated with metallic coatings, Which provide adequate protection for many years. The metallic coating corrodes preferentially to the mild steel of cast iron and subsequently. Depletes with time. This results in corrosion of the carbon steel substrate,which may cause failure . In most cases once corrosion has started on these components, replacement would be recommended due to the practical difficulties in corrosion protection,Testing fo corrosion protection systems prior to use is therefore extremely important.
All of hardware on a line,glass and pin insulators are usually most effected by corrosion because of their physical shape and orientation on the line.Corrosion of the insulator pin occurs due to corrosive mediums(dirt/dust)collecting at the pin-cement interface within the pin holder. The orienttion of the disc,while in-service(pin facing to ground)also prevents the pin holder area being washed clean during rain,resulting in a localised corrosive cell forming at the pin holder area. The galvanising protective layer is corroded away and general corrosion fo the steel substrate takes place .The rate of the corrosion is sometimes accelerated by the presence fo leakage currents due to dirty insulator discs(pollution of discs).Pin corrosion is more prominent within the first three to four discs within a string of insulators.