General metal corrosion can lead to valve orifice plugging
(photo courtesy of Innovative Group)
October 2018 SPRAY 37
The degradation of materials includes loss of:
• Package metal
• Polymer coating or film properties, such as the ability
of a coating or film to be a barrier between its metal
substrate and the environment (i.e., a formula)
• Adhesion between a polymer and its substrate metal
(delamination)
There are several types of possible spray package failures
modes:
• A package leaks product, propellant or both
• A package no longer sprays but is still partially full
• The product has a malodor
• The product is discolored
• The product’s active ingredients are below their
specified concentrations
Different types of corrosion lead to various failures modes.
The different types of corrosion that contribute to or cause
different types of spray package failures are:
General metal corrosion
• Malodor
• Discoloration
• Valve orifice plugging
• Decreased concentrations of active ingredients
Localized metal corrosion
• Leaking product
• Leaking propellant
General polymer corrosion
• Delamination of film or
coating from substrate metal;
could cause valve orifice
plugging when there are
free-floating coating or film
particles
Localized coating or laminate
film corrosion
• Blisters—typically do not
cause package failure unless
blisters become free-floating
polymer particles and plug
valve orifices
Hybrid corrosion consisting of
polymer delamination and metal
corrosion under the delaminated
polymer coating or film
• Malodor
• Discoloration
• Product leaking
• Propellant leaking
• Valve plugging
Material corrosion with subsequent
package failure cannot be predicted
using first-principles. Fortunately,
corrosion tests are available to determine if material corrosion is
possible, how fast materials are corroding and the length of service
life when package materials corrode. Corrosion testing could be
either a conventional storage test (conducted for at least one year)
or a shorter length electrochemical corrosion test.
Integrating a company corrosion database with results from corrosion
testing will help prevent surprise corrosion that leads to a
disrupted market or a delayed new product introduction.
Thanks for reading Corrosion Corner and I’ll see you in November.
SPRAY