الفهرس 
Experimental techniques
Chemicals for Electroless Nickel BathsOnly 14 pages are availabe for public view
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Abstract
The present study investigates the electroless deposition of
binary Ni-P and ternary Ni-Sn-P on aluminum substrate in
alkaline bath, as well as, studying the chemical, mechanical and
electrochemical properties of the binary and ternary alloys.
The experimental results obtained and their interpretation is
included in chapter III.
Chapter III deals with electroless nickel plating from
alkaline bath containing sodium hypophosphite as a reducing
agent and sodium citrate as a complexing agent. Also, the
optimum compositions and operating conditions for deposition of
Ni-P and Ni-Sn-P deposited alloys at 85oC are shown in the
following table.
Chemical Name Chemical formula Concentration
Nickel sulphate NiSO4.7H2O 20g/l ●
Sodium hypophosphite NaH2PO2.H2O 15g/l ●
Sodium citrate Na3C6H5O7.H2O 35g/l ●
Lactic acid CH3CH(OH)COOH 3.7ml/l ●
Ammonium sulphate (NH4)2SO4 25g/l ●
Tin chloride SnCl2 0.005 to1g/l ▲
Ammonium hydroxide NH4OH pH adjust (8, 8.5 and 9)
Temperature 0C 850C The elements percentage of the constituents in Ni-P and NiSn-P deposits, deposited from alkaline bath, are shown in the
following table.
Type of coating Before heat treatment After heat treatment
Wt % Wt %
Ni% Sn% P% Ni% Sn% P%
Ni-P 86.5 - 13.5 89.3 - 10.7
Ni-Sn-P
(0.1gmSnCl2)
82.60 2.54 14.86 78.67 1.97 19.36
Ni-Sn-P
(1gm SnCl2)
79.90 8.00 12.10 78.16 12.86 8.98
The deposition rate of electroless Ni-P increases with an
increase in the time of deposition, bath temperature and pH.
The deposition was found to be an amorphous structure in
the as deposited form, where as strong crystalinity was observed
at 400oC for 60 minutes. The sharp peaks formations of nickel and
nickel phosphide Ni3P were detected at 400 oC.
The morphology of electroless nickel alloy coating on
aluminum substrate has a nodular shape.
The results showed that all samples have excellent adhesion,
and no gaps.All the electroless nickel coating alloys showed excellent
corrosion resistance in sodium chloride, sodium hydroxide and
hydrochloric acid solutions compared with aluminum substrate.
This is because of the formation of a surface protective film with
absence of grain boundaries, dislocation, kink sites and other
surface defects.
Also, it is attributed to the nanocrystalline size of the binary
and ternary alloy deposits.
The potentiodynamic polarization of the ternary alloy were
studied at different pH values and showed that as the pH values
decreased the corrosion resistance increase.