Corrosion Resistance of Phosphorus-Clad Iron Powders in Biological and Inorganic Media

Abstract

The manufacture and use of clad iron-based powder materials is a promising trend of powder metallurgy which allows variation in their technological and magnetic properties in wide ranges. The corrosion properties of iron powders clad with phosphorous and their interaction with biological media of the living organism are studied. The PZhRV 3.200.26 (Ukraine), АНС 100.29 (Sweden), and PZhV 200 (Russia) iron powders with different particles sizes are clad with phosphorous by the method of thermochemical decomposition of phosphorous compounds and by the method of thermochemical synthesis in a vibrating bed. Corrosion tests of the iron powders clad with phosphorous are performed in a 3% NaCl solution. Calculations of the depth corrosion factor show that the clad powders are much more resistant to corrosion in the aggressive medium (3–4 points according to the ISO 11130:2010 standard) than the initial powders (1 point). The low values of the depth corrosion rate of the powders clad with phosphorous indicate that surface corrosion proceeds on powder particles. It is shown that the interaction of initial PZhRV 3.342.28 and AHC 100.29 iron powders with human blood plasma is 5.8 and 7.2 times much more intensive, respectively, than that for PZhRV 3.342.28 and AHC 100.29 powders clad with phosphorous. On the surface of the iron powders, phosphorous interacts with plasma proteins to form a protective colloid biocomplex, which increases substantially the resistance of the clad powders in blood plasma. Thus, the cladding of iron powders with phosphorous enhances significantly their chemical stability both in human blood plasma and in air.