Effect of bath agitation on surface properties and corrosion behaviour of ENi-P coatings along with annealing temperature

Electroless Nickel-Phosphorus (ENi-P) coating has been considered to be one of the better surface engineering techniques for numerous mechanical, chemical, electrical and electronics applications. However, the achievement of desired coating standards and improved properties of the as-deposited substrate largely depends upon rigid process control measures adopted during the coating process. Towards this, the coating bath chemistry, operating parameters, preparation of surface, and the equipment being used are a few critical variables that have influence on coating deposition rate, uniformity, smoothness and brightness. Endeavour of the present study is to analyze the effect of bath agitation on the properties of ENi-P coatings, with and without heat treatment, carried out on mild steel (MS) as the base material or substrate. Results revealed that a heavy agitation and annealing at 400 °C resulted in 118% increase in microhardness values as against non coated sample without heat treatment. A sharp reduction corrosion rate was observed in the deposit obtained from bath A with nil agitation, as against non-deposited sample. Hence, bath agitation and annealing temperature are pivotal in governing the properties of deposits, thereby enabling manufacturing of substrates and surfaces for specific application and also preventing regular or early failures, with improving service life.