January 2020 SPRAY 37
Insecticide chemicals are often electrochemically active
and thus corrosive toward spray packaging. Typically,
insecticide formulas also need a corrosion inhibitor to
prevent or control spray package corrosion…
Changes to raw material suppliers for existing formulas
The chemical composition of raw materials from different suppliers
might be different. Consequently, corrosion testing should
also be conducted when changing raw material suppliers.
Changing surfactant suppliers, types
and concentrations for existing formulas
Surfactants make a surface more or less susceptible to wetting by
formula ingredients, formula water and contaminant water. Thus,
corrosion testing should be conducted when changing the type of
surfactant or your surfactant supplier.
Changing fragrance types, suppliers and/or concentrations
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. Consequently, changes to
the type of fragrance, fragrance supplier and fragrance concentration
in your formula should be tested for changes in corrosion.
Unexpected spray package corrosion can be very costly and disruptive
to product development programs. Indeed, the cost of unexpected
corrosion typically greatly exceeds the cost for complete
corrosion testing. Consequently, the answer to the when-to-test
question is virtually everything should be tested, or—if available—
a proprietary, comprehensive company corrosion database should
be consulted to determine if corrosion testing is needed.
In Chapter 7 of the Pair O Docs Elements of Spray Packaging
Course short course we discuss various types of corrosion tests.
Basically, corrosion testing could be either a storage stability test
for a year or more, or a shorter electrochemical corrosion.
Test results from shorter storage times, such as three months,
could be misleading and result in unexpected spray package
corrosion in commercial products. Using higher temperatures
to accelerate corrosion typically leads to high risk, incorrect and
confusing predictions about actual corrosion. For example, three
months of storage testing at 40°C (104°F) does not correspond
or predict the corrosion that will occur after 2–5 years storage at
room temperature.
Electrochemical corrosion tests can accurately predict 2–5
years of actual spray package corrosion in less than 100 days
when the appropriate test parameters are used for the electrochemical
test.
Please visit www.pairodocspro.com for more information. Thanks
for reading and I’ll see you in February. SPRAY