The main subject of the thesis is the investigation of palladium-iron alloy electrodeposition
from aqueous solutions in general. Palladium-iron alloy deposits could be in
principle a substitute for nickel or nickel-palladium deposits to avoid metal dermatitis.
Nickel contact dermatitis is an especially sensitive allergy caused by decorative or
functional use of nickel: it needs to be avoided in a number of applications.
Electrochemical and chemical experiments have been carried out on several solutions
with variable pH, salts and metal complexes to design a chemical and electrochemical
stable electrolyte for palladium-iron alloy electrodeposition. Electrochemical
measurements, physical and chemical analysis techniques, mechanical, optical,
chemical and electrochemical measurements methods as well as different corrosion
tests were used to describe the electrochemical processes and the properties of the
Investigations have shown that from ammoniacal electrolytes electrodeposition in a
wide range of composition is possible (pH = 7.5 - 10.5). Electrolyte consists of palladiurn
as Pd(NH3)4CI2 and iron as iron(ill)-citrate. Composition of the deposited alloys
depends mainly on the ratio of the metal ions in the electrolyte, while the effect of
current density and electrolyte temperature is slight. Current efficiency depends on
iron concentration in the electrolyte and is a maximum of ca. 85 %. Palladium-iron
alloys with a higher content of palladium (>80.-%) show cracks because of the
high internal stress (tensile stress) of those layers. Alloys with smaller content of
palladium (<20 wt. -%) are less sensitive to cracking.
Wear resistance and corrosion resistance of the palladium-iron alloys are similar or
sometimes better to palladium, palladium-silver, palladium-cobalt or palladium-nickel
deposits. Hardness of the palladium-iron layers increases with increasing iron content
from 200 to 600 VHN. Contact resistance is low in the range of 0.5 to 1.5 mfl
and barrier layer properties are excellent for gold and copper diffusion during services
up to 160 degrees Celsius for 240 hours.
Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.