However , when a metal surface is subjected to severe rubbing or to a stream of impacting particles the passive film damage becomes continuous and extensive .
Nevertheless , they can provide excellent corrosion protection because if damaged accidentally they spontaneously self - heal by metal oxidation .
When a metal surface is subjected to severe rubbing or to a stream of impacting particles the passive film damage becomes continuous and extensive .
Nevertheless , they can provide excellent corrosion protection because if damaged accidentally they spontaneously self - heal by metal oxidation .