Corrosion Resistance of Electroless Ni-P-SiC/ Ni-P-TiO2-ZrO2 Nano-Coatings in Paper Mill Bleach Plant

In present investigation, electroless Ni-P-SiC/Ni-P-TiO2-ZrO2 nano-composite platings have been deposited upon mild steel substrate (AISI 1040). A homogeneous and consistent allocation of SiC, TiO2 and ZrO2 nano-particles into EL Ni-P matrix is recognized in as plated and heated (400°C) coupons respectively through SEM and EDAX methods. The investigated coupons exhibited resistance against corrosion in order as: 254SMO > SS2205 > Ni-P-TiO2-ZrO2 as-plated > Ni-P-TiO2-ZrO2 heat treated > Ni-P-SiC as-plated > Ni-P-SiC heat treated > SS316L. The corrosion resistance seems too dependent upon Cr, Mo and N content and hence correlate well with the PRE number of the respective alloys. The conventional materials of construction SS 316L are not suitable for both C and D washers. Avesta 254SMO shows immunity to attack in these environments. On the basis of corrosion resistance, mechanical properties and cost comparison, Avesta 254 SMO seems acceptable material for gaseous phase of C and D washers while duplex stainless steel 2205 and Ni-P-SiC/Ni-P-TiO2-ZrO2 as-plated and heated coatings seems acceptable for the other application in these washers.