Igwe igwe anaghị agba nchara ngwa ngwa, nchara ma ọ bụ mebie mmiri dị ka ígwè nkịtị si eme. Otú ọ dị, ọ bụghị ihe na-egosi ntụpọ zuru oke na ikuku oxygen dị ala, nnu dị elu, ma ọ bụ gburugburu ikuku ikuku na-adịghị mma. E nwere ọkwa dị iche iche na elu elu nke igwe anaghị agba nchara ka ọ dabara na gburugburu ebe alloy ga-atachi obi. A na-eji igwe anaghị agba nchara ebe achọrọ ma njirimara nke nchara na nguzogide corrosion.

Igwe anaghị agba nchara dị iche na carbon steel site na ọnụọgụ chromium dị ugbu a. Nchara nchara carbon na-enweghị nchekwa na-adị ngwa ngwa mgbe ekpughere ikuku na mmiri. Ihe nkiri iron oxide a (nchara) na-arụ ọrụ ma na-eme ka corrosion dịkwuo elu site n'ịmepụta oxide iron ọzọ[n nkọwapụta dị mkpa]; na, n'ihi nnukwu olu nke ígwè oxide, nke a na-agbawa ma daa. Igwe anaghị agba nchara nwere chromium zuru oke iji mepụta ihe nkiri na-agafe agafe nke chromium oxide, nke na-egbochi nrụrụ ihu n'ihu site na igbochi mgbasa oxygen n'elu igwe ma na-egbochi corrosion ịgbasa n'ime ụlọ nke metal ahụ. Passivation na-eme naanị ma ọ bụrụ na oke nke chromium dị elu ma ikuku oxygen dị.