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These additives are usually proprietary to the electroplating salt manufacturers and it is
difficult to find information on what they are. They are frequently organic chemical
compounds.
During plating, it is usual to agitate or stir the electrolyte to maintain optimum plating
conditions and uniformity of composition.
The anode area and position are important to efficient electrodeposition and uniformity of
deposit. There is a tendency for plating to be thicker on cathode areas closest to the
anode and thinner in areas hidden (or out of line of sight) from the anode. Correct
positioning of the anodes (more than one may be used) and a large anode area
(compared to cathode area) is desirable for good plating.
The electrical conditions during plating are also important for plating quality. In particular,
the current density (the current divided by surface area of the piece) plays an important
role, particularly in alloy plating where deposit composition is controlled by current
density. If the current is too high, the plating speed is increased but one may get a porous,
dendritic deposit rather than a bright one and it may be accompanied by gas evolution
which affects the surface finish. If it is very low, then the deposit may not have a good
appearance and plating will be slow.
The temperature of the electrolyte can also play a role in getting good plating, particularly
in alloy plating. Follow the electrolyte supplier’s recommendations.

Surface Preparation

For good quality electroplating and good adhesion of the deposit, the condition of the
surface to be plated is important. Most plating defects arise from unclean surfaces prior
to plating. The surface to be plated must be clean and free from grease, dirt, oxides and
tarnish films, polishing compounds, etc. Greasy, dirty surfaces will not be wetted by the
electrolyte and may not be plated. It also helps to have a smooth polished surface, free
from defects and imperfections, if one wants a bright polished electroplated deposit.
Plating should not be used to hide defects and to improve the surface polish (reduction in
surface roughness). Defects to be avoided include casting porosity, inclusions and
embedded polishing compounds, scratches and tool marks, and pitting from over-pickling.
The surface to be plated (the ‘substrate’) can be prepared by normal polishing techniques
and then cleaned in several ways:
 Ultrasonic cleaning in detergent solution
 Degreasing in solvents, preferably in an ultrasonic bath
 Acid cleaning with pickling acids
 Steam cleaning under a high pressure jet of steam
 Electrolytic cleaning; this can also activate the surface.
 Chemical cleaning with reagents, often at high temperatures.
In practice just one, or possibly two, techniques are used, for example degreasing and
acid pickling, followed by rinsing in water and drying. Many proprietary cleaners are
alkaline with wetting agents and surfactants added. Deionised or distilled water should be
used as the final rinse before drying to prevent any deposits from the water being left on
the surface.