Corrosion protection of sintered metal parts by coating deposition. Part I: microstructural characterization

The presence of the structural interconnected porosity causes serious problems in the use of traditional bath compositions or usual deposition methods for protecting sintered iron pieces. The corrosion protection of steel is traditionally obtained by different surface treatment methods such as painting, electroplating, dipping or spraying, which cannot always be easily transposed for sintered metal parts. The aim of this work is to study in detail a wide range of industrially produced coatings, covering all the main proposed treatments, in order to evaluate the microstructural characteristics and in particular to point out the structural defects which can affect the corrosion behaviour of the protected sintered metal parts. The samples studied in this work were obtained by industrial production; both the sintered substrates and the corrosion protection treatments were carried out by specialized factories.