W. Stephen tait, ph.D.
Chief Science Officer & principal Consultant,
pair O Docs professionals, LLC
Corrosion Corner
When is spray package
corrosion testing needed?
Happy New Year, everyone. One of the most frequent
questions that I’m asked is, “When is corrosion testing
required for spray packaging?”
Spray packaging corrosion risks without corrosion testing or
a comprehensive company corrosion database is approximately
62% for aerosol containers and approximately 20% for laminated
metal foil packaging.
Thus, high risk comes with incomplete corrosion testing or corrosion
tests using the wrong test parameters. Consequently,
your best defense against spray product failures and litigation from
unexpected corrosion is a complete and robust corrosion testing
program. Hence, I recommend that corrosion tests should be
conducted on the following:
New products
Corrosion science is not advanced enough at this time to
where chemistry first principles can be used to determine
if a given formula’s chemical composition is or is not corrosive
toward the different types of spray packages. Consequently, corrosion
testing is needed to avoid high risk.
Derivations of existing products
(line extensions or derivatives)
Small changes to the chemical composition of a formula could
transform a benign formula into a spray package-eater. Thus,
derivative formulas (or line extensions) should be tested for corrosion
compatibility with the chosen spray package, no matter how
small the change to the formula.
All new insecticide formulas and derivative
insecticide formulas
Insecticide chemicals are often electrochemically active and thus
corrosive toward spray packaging. Typically, insecticide formulas
36 Spray January 2020
also need a corrosion inhibitor to prevent or control spray package
corrosion.
When developing a corrosion inhibitor
Corrosion testing is needed to find a suitable inhibitor for a
corrosive formula. Corrosion inhibitors typically have an effective
concentration range and corrosion testing is also needed to determine
the effective range.
Your best defense against
spray product failures and
litigation from unexpected
corrosion is a complete
and robust corrosion
testing program…
Anhydrous formulas and derivative anhydrous formulas
Anhydrous formulas are typically contaminated by small amounts
of water. Water is electrochemically active and causes metal
corrosion. Consequently, anhydrous formula corrosion testing
is needed to determine if the formula is corrosive with a given
concentration of contaminant water and to determine the safe
concentration range for contaminant water.
New and derivative low pH formulas
PH is the negative log of hydrogen ion concentration in moles
per liter. Hydrogen ions are electrochemically active and cause
corrosion of spray package metals and metal foils. Consequently,
low pH formulas should be tested for corrosion with all types of
spray packages.
New and derivative high pH formulas
High pH formulas can also cause spray package corrosion. Thus,
corrosion testing is also needed for high pH formulas.
Changes to an existing formula’s chemical composition
Small changes to the chemical composition of a formula could
transform a benign formula into a spray package-eater. Thus, any
change to the chemical composition—no matter how small the
change—should be tested for corrosion.
Changing package materials for existing formulas
Changes to package materials could include different types of
polymer coatings or laminate films; different coating thicknesses
and/or different package metals. The chemical composition of a
formula determines if a given type of package material is resistant
to corrosion. Thus, corrosion tests should also be conducted
when switching package materials.
While many fragrances offer some modicum of
corrosion inhibition, there are also a few types of
fragrances, such as those incorporating vanilla,
that often cause corrosion…