Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 1, pp. 29−34.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © I.V. Petukhov, N.A. Medvedeva, S.S. Mushinskii, M.R. Nabiullina, 2012, published in Zhurnal Prikladnoi Khimii, 2012, Vol. 85,
No. 1, pp. 32−37.
INORGANIC SYNTHESIS AND INDUSTRIAL
Possible Reasons for the Appearance of Metallic Phase
in Electroless Nickel Plating Solutions
I. V. Petukhov, N. A. Medvedeva, S. S. Mushinskii, and M. R. Nabiullina
Perm State University, Perm, Russia
Received December 13, 2010
Abstract—The growth of Ni–P coatings was studied in the “stable” electroless nickel plating solution and in the
“decomposed” solution containing in its bulk a sufﬁ cient amount of the metallic phase particles.
Electroless nickel plating is a technique used exten-
sively in the preparation of protective and decorative, as
well as functional coatings. It is known that metal phase
particles are accumulated in the bulk of electroless nickel
plating solutions during prolonged exploitation. As a re-
sult of progressive accumulation of the metal phase in
the bulk of the solution and on the bath walls the deposi-
tion onto the surface being coated is completely ceased.
This process is called “decomposition” of the electroless
nickel plating solution. Removal of the metal particles
requires continuous ﬁ ltering of the solution so as the
wasteful expenditure of chemicals could be prevented.
It was presumed that the metal particles are formed by
homogeneous nucleation  which process, according to
classical nucleation theory, requires much energy. Also,
it was supposed that the metal phase particles are formed
in close proximity to the growing surface . Factors re-
sponsible for the appearance of the metal phase particles
in the bulk of the solution, which speciﬁ cally initiates the
solution decomposition, still remain to be conclusively
The Ni–P coatings were deposited at 343–363 K under
temperature-controlled conditions from the solution with
the following composition, M: NiCl
COONa 0.127, pH 4.5.
The coatings were deposited onto carefully polished
20Kh13 steel samples.
The substrate surface was pretreated by degreasing
with Vienna lime, washing with distilled water, and
pickling in hydrochloric acid (1:1) for 30 s. The loading
capacity was 1.0–1.5 dm
The structure of the coatings was examined on
a NewView-5000 Zygo interference microscope– non-
contact proﬁ lometer. The resulting microproﬁ les were
processed to determine the following surface roughness
parameters of the coatings: PV, the maximum peak to
valley height of the surface proﬁ le; R
, roughness average;
rms, root mean square deviation of the peak and valley
from the centerline; and R
, average absolute value of the
ﬁ ve highest peaks and ﬁ ve lowest valleys. Well-resolved
proﬁ les of spherical segments were chosen for statistical
The surface structure and composition of the coatings
were analyzed using a Hitachi S-3400N scanning electron
microscope equipped with a Bruker energy dispersive
The coatings grown on the carefully polished steel
~ 4 nm) have a fairly smooth surface proﬁ le.
During growth of the Ni–P deposit, spherically shaped
segments strongly extended in the substrate plane are
formed on the surface (Fig. 1). Table 1 presents the results
of processing of the microproﬁ les obtained.
The average radii r
and average heights of the spheri-
cal segments h
, as well as their average ratios
determined by averaging 80–150 experimental values.
Because the spherical segments are strongly extended