Effect of pH values on nanostructured Ni–P films

Abstract

Electroless Ni-P films were deposited on mild steel substrate and sodium dihydrogen phosphite was used as a reducing agent. Temperature and pH of the bath were maintained at 90°C and 6.86 to 10.86 respectively. The Ni-P film deposited samples were characterized by FE-SEM to know the surface and cross-section morphology of the film and the phases present were examined by X-ray diffraction. The chemical composition of the electroless Ni-P films was determined by EDS analysis. The thickness of the film was determined by FE-SEM cross-section image and was nearly 5 lm. The influence of pH values on film morphology was studied. Ni-P film was obtained in the pH ranges between 6.86 and 10.86 on mild steel substrate. Ni content in the film increased with increasing pH value of bath solution. Dense, uniform and small spherical shape grains were found in Ni-P film deposited at pH = 10.86. X-ray analysis shows a (222) preferential growth in all the films. The mean crystallite size of Ni-P films deposited at pH 6.86, 7.86, 8.86, 9.86, and 10.86, calculated by using the Scherrer-equation was found to be 44.7, 40.4, 41.2, 34.6 and 30.4 nm, respectively.

Preparation of Sol-Enhanced Ni–P–Al2O3 Nanocomposite Coating by Electrodeposition

“…Near the area with high H + concentration, the deposition rate is low due to the slow formation and growth of crystal nucleus, resulting in thin coating and no significant improvement in hardness. Similar situations have been reported in a similar pH bath [24,25]. Besides, it has been pointed out that the pH of the plating solution has an effect on the P content of the coating, that is, the hardness of the coating increases with the decrease of P content [26].…”

Full Optimization of an Electroless Nickel Solution: Boosting the Performance of Low-Phosphorous Coatings

“…All the coatings showed the typical nodular growth with cauliflower-like endings randomly distributed on the surface showing differences in size and nodules distribution. Among the different factors able to impact surface topography, pH and the nature and concentration of complexing agents are the most important ones and, presumably, they act together (i.e., mixed effect) on surface topography of electroless nickel coatings [ 28 , 29 , 30 ].…”

Influences of Bath Chemistry and Plating Variables on Characteristics of Electroless Ni–P Films on Si Wafers from Alkaline Citrate Solutions

“…Electroless Ni-P deposition reaction can occur in an alkaline or acid environment. To study the autocatalytic deposition of Ni accompanied by P incorporation in the film, it is necessary to know the effect of the operating parameters and bath chemistry on the deposition rate and the quality of the deposits, such as the substrate nature [16], pH [17,18], plating temperature [19], stirring [20], light [21], stabilizers [22], complexing agent [23], and additives [24]. In order to perform deposition of electroless Ni-P, the substrate surface needs to be preactivated and presensitized.…”

“…However, the deposition rates decreased with the increase in sodium citrate. Rahman and Jayaganthan [18] studied the effect of pH on electroless Ni-P films on the surface of mild steel and concluded that the Ni content increased with increasing pH. Moniruzzaman and Roy [17] reported that electroless Ni-P coating was produced on carbon steel and polypropylene substrates and pointed out that the coating of good appearances was obtained in the pH ranges between 5.5 and 12.5 on carbon steel and between 8.5 and 12 on the polypropylene.…”