39 NACE INTERNATIONAL: VOL. 55, NO. 12 MATERIALS PERFORMANCE DECEMBER 2016
visually inspected for mudcracking. e
highest DFT reading on each sample with-
out mudcracking was recorded. With the
addition of fibers to the formulation, the
researchers noted that the dry film toler-
ated substantially higher DFTs without
mudcracking.
Additional work was done to modify the
formulation to reduce cure times, and a
similar test was carried out with varying
degrees of catalyst modification to deter-
mine if the film stability documented in
earlier tests could tolerate decreased cure
time. e formulators saw a clear correla-
tion between the addition of fibers and
their ability to formulate IOZs that could
tolerate higher DFTs while still producing
satisfactory dry times.
To fully assess the benefits of the fiber
additive and ensure the IOZs' corrosion
protection properties were not negatively
affected when used in a traditional three-
coat paint system, testing of samples with a
coating system comprised of a 60- µ m coat
of IOZ, a 160- µ m coat of epoxy, and a 60- µ m
coat of urethane was done according to
ISO-12944-6, "Paints and varnishes—
Corrosion protection of steel structures by
protective paint systems, Part 6: Laboratory
performance test methods." e formula-
tors also performed a salt spray test,
ISO-72539, "Paints and varnishes—Deter-
mination of resistance to neutral salt spray
( fog)," that constantly sprayed the samples
with a 5% sodium chloride (NaCl) solution
at 35 °C. is evaluated the corrosion resis-
tance of the coating systems by reproducing
the conditions that occur in an atmosphere
containing salt spray or splash.
e resulting data confirm that inor-
ganic mineral fibers added to IOZ formula-
tions substantially improved mudcracking
resistance (up to 80%) without sacrificing
corrosion performance. Also, because of the
increased stability of the IOZ film, the for-
mulators learned that cure times for these
coatings could be accelerated, the IOZ's
dry-to-recoat time could be reduced by
nearly half, and the films still resisted mud-
cracking at excessive DFTs.
More information on the study can be
found in CORROSION 2016 paper no. 7835,
"Making Mud-Cracking IOZ's a ing of the
Past," by J. McDonald, D. Morton, L.T.
Pederson, and P. Bernad.
e
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