Electrochemical Corrosion of Sintered Composites on the basis of Fe/FePO4 Coated Powders

• Published in: International journal of electrochemical science 2016, Vol.11 (2), p.1751-1764
• Main Authors: Hvizdoš, Pavol, Dudrová, Eva, Kabátová, Margita, Oriňaková, Renáta
• Format: Article
• Language: English
• Subjects: corrosion behaviour; electrochemical corrosion; microstructure; Sintered composites iron/iron phosphate
• ISSN: 1452-3981; 1452-3981
• DOI: 10.1016/S1452-3981(23)15958-X

Electrochemical corrosion behaviour of sintered composites based on iron powder consisting of spherically and/or irregularly shaped iron particles precipitation coated with FePO4 layer was studied using the potentiodynamic polarization test. The Fe/FePO4 coated powders containing 2 and 5 wt-% of FePO4 were compacted to the density of 6650-6700 kg m-3 and subsequently sintered at temperatures ranging from 912 to 1130°C for 3 min in air. The creation of a liquid phase during heating to1130°C with subsequent quenching into water and/or into liquid nitrogen resulted in the formation of a thin and continuous iron phosphate layer consisting of ~ 85 wt-% of fine lamellar phase identified as graftonite and ~ 15 wt-% of iron oxides - wüstite, magnetite and hematite. Thus prepared composites show an improvement in anti-corrosion behavior, which is associated with the formation of a protective continuous layer. Silica nano-powder particles tend to agglomerate, which results in discontinuities in the protective iron phosphate layer, with a detrimental effect on corrosion behavior of these composites.