Influence of electroless Ni-P deposits on the corrosion-fatigue properties of an AISI 1045 steel

Electroless nickel (EN) deposits containing approximately 10% phosphorous and about 20 mu m thickness are shown to increase the corrosion-fatigue properties of the AISI 1045 steel in the stress amplitude range of 221-331 MPa, in the presence of an aqueous solution of 3% NaCl. Such an increase is enhanced if the coating is in the as-deposited condition rather than post-heat treated at 473 K for 4 h, despite the fact that such a treatment produces an increase in hardness. The improvement observed in corrosion-fatigue properties is also more pronounced as the stress amplitude decreases. The monotonic mechanical properties determined under tensile conditions are not affected by the presence of the coating. The inadequate agitation of the bath has given rise to microporosities and 'orange-peel' type effects associated with the deposit which are believed to be related to the trapping of hydrogen bubbles. (C) 1997 Elsevier Science S.A.