Finishing - September-October 2021

32 ELECTROPLATING
A cost-effective solution to
retouching electroless nickel
Widely used across multiple industries,
nickel and nickel alloy surface coatings
create a tough finish that can possess
significant wear and anti-corrosion properties.
This makes these coatings indispensable for
critical applications, especially where harsh
conditions are prevalent such as in aerospace,
marine, petrochemical, and the oil and gas
industries. In particular, Nickel-Phosphorous
plating alloys have grown in popularity due to
several unique physicochemical properties.
While Nickel-Phosphorous alloys can be
applied electrolytically, they are more
commonly applied through an electroless,
autocatalytic process due to the unique ability
to provide coating uniformity across complex
geometries – making them ideal for OEM
components. Known as electroless plating, this
technique does have some drawbacks though.
Namely, this is when you need to repair or
replate electroless Nickel-Phosphorous (ENP)
coated parts.
To explain, as ENP plating happens in an
immersion tank, replating of already coated
areas can cause the part to be out of
tolerance due to excess buildup of material.
To overcome this, there needs to be either
significant – if not cost prohibitive – masking,
or risky chemical stripping of the entire part
before replating.
There is an alternative to the above though,
and that is selective electroplating. This
process is focused only on limited, specific
surfaces of a part rather than the entire
geometry, so the issue of coating uniformity
across varying geometries is no longer a
concern. Consequently, when it comes to
repair, touch-up and refurbishment of ENP
coated parts, the selective plating process
provides a viable option that can save
significant time and cost. Components that
might ordinarily be scrapped, can be saved all
without compromising the quality or integrity
of the part.
The Traditional ENP repair
option:
The traditional method of retouching or
repairing ENP components, involves stripping
and replating the entire part; requiring the
removal of the component from its setting,
immediately creating downtime.
There are other significant
drawbacks to the traditional
method of ENP repair as well.
The repair of damaged ENP components
often involves chemical stripping of the entire
part which can come with the substantial risk
of damaging the part beyond repair. While
masking is possible, it can be complex and
time consuming. Similar issues apply with
original equipment manufacture, where mismachining
after plating can compromise
quality, leading to scrap and waste. Equally,
even small damage such as minor scratches in
transit can result in rejection of the part.
So, while returning components for
electroless nickel plating is an option, it
inevitably involves more time, cost and risk.
Which is where selective plating such as the
SIFCO Process® really come into its own, as
many world-class manufacturers have
discovered.
The advantage of being
selective.
With selective plating, the key word is
Finishing - September/October 2021
continues on page 34