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 Nital Etch Inspection is a non-destructive testing technique
used to evaluate the effects of poorly controlled
manufacturing processes such as machining, grinding and heat
treatment on metallic components.
Using a
Nitric acid solution, machined components are etched
revealing grinding and machining abuse. The nital acid
etchants work by forming a coloured surface film on the
steel and attacking its surface to form pits.
Under certain circumstances machining and
grinding can introduce sufficient heat in a component to
heat-treat its surface, this is generally local over-heating
and can produce undesirable changes in material
properties. An example occurred in the late 1960’s when a
helicopter of the Queen’s flight crashed killing 4 crew.
The aircraft lost a rotor blade due to the effects of
grinding abuse on the main rotor shaft. Shortly afterwards
the society of British Aerospace companies recommended the
use of surface acid etch inspection. This inspection method
is now widely used throughout the aerospace industry to
detect this type of abuse.
Aerotech
carry out etch inspection on many components for the
Aerospace industry using our specifically designed etch
inspection unit and viewing area.
As part of
their ongoing expansion into the Aerospace field, Aerotech
have recently been approved by Goodrich Actuation Systems
(formerly TRW Lucas Aerospace) to carry out their Nital Etch
Inspection to Specification 981-060-016.
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