C o n v e n t i o n a l C u r r e n t E l e c t r o n s E l e c t r o n s E x t e r n a l C i r c u i t C a t h o d e E l e c t r o l y t e A n o d e F igure 1 Bimetallic couple Zinc coating Steel discovered is protected Base steel Galv anizing offers sacrifcial protection Rust tak es its toll on painted surfaces Here is what happens to painted steel when scr atchedT he exposed steel corrodes and forms a rust bubble T his bubble larger than the surface occupied by the steel will expand and lift the paint off the surface creating a blister In the meantime the cavity of corrosion and the blister continue to progress Here is what happens in the case of galv anized steel when scr atchedT hanks to its galv anic protection the zinc coating sacrifces itself to protect the steel to which it is bonded T his sacrifcial protection will prev ail as long as zinc is within pro ximity Should the hotdip galv anized coating be damaged or scr atched the steel will fnd protection against corrosion thanks to the surrounding zinc that has higher electrochemical properties than those of steel Since corrosion is an electrochemical process it will attack the surrounding zinc r ather than the exposed steel T hus said contr ary to other types of processes claiming to corrosion protection it is not required to touchup noticeable cr acks faws or gaps on galv anized coatings 14