Tnemec's Zinc-Rich Primer Stands Test of Time Protecting Potable Water Tanks from Corrosion
(KANSAS CITY, Mo., August 24, 2007) – Since 1997, when Tnemec pioneered the first
organic zinc-rich primer to be ANSI/NSF Standard 61 certified for potable water
tank interiors, the interior and exterior of more than 5,000 potable water
tanks have been coated with Hydro-Zinc coating systems, according to Doug
Hansen, director of sales, Water Tank Market. “Organic zinc-rich primers have gained a high
level of acceptance throughout the water tank industry based on a decade of proven
performance in providing long-term corrosion protection for the interior and
exterior of potable water tanks,” Hansen noted.
As the leading provider of coatings for water storage tanks, Tnemec has monitored field evaluations of its Hydro-Zinc primer over the past decade. The divers performing these inspections repeatedly described the interior surfaces as being “in very good condition” with “no signs of peeling, cracking, or blistering,” Hansen said.
The product has also been evaluated using American Society for Testing and Materials (ASTM) methods involving salt fog, adhesion, recoat and other performance criteria. This combination of field evaluations and accelerated testing confirm that when topcoated as part of a system, Hydro-Zinc provides both barrier and galvanic corrosion protection on the interior and exterior of potable water tanks.
“This dual protection offers significant benefits over barrier-only coatings,” Hansen reported. “If a holiday or damage of the barrier topcoat occurs, the organic zinc-rich primer takes over and provides galvanic protection. Coating systems with Hydro-Zinc can be expected to last 40-50 percent longer than conventional interior two-component epoxy and exterior epoxy/aliphatic urethane systems for extended protection.”
Hansen credits the popularity of Hydro-Zinc in water tank fabrication shops and field applications to properties such as rapid cure and extended maximum recoat times. “Hydro-Zinc can be topcoated with epoxy in four hours at 75 degrees F and 50 percent relative humidity,” Hansen said. “When applied and cured in accordance with Product Data Sheet instructions, a zinc-rich urethane/epoxy coating system can be placed in potable or fresh water immersion service without the threat of blistering.”
The urethane zinc-rich primer exhibits “dry fall” properties when applied with conventional application equipment such as airless and air spray. “This is especially advantageous when spray applying Hydro-Zinc to tank exteriors in tight, confined locations,” Hansen acknowledged.
Available in two component (Series 91-H2O) and
single component (Series 94-H2O) formulations, Hydro-Zinc contains
low levels of Hazardous Air Pollutants (HAPs), as well as a low level of volatile
organic compounds (VOCs), making it compliant for both shop and field
applications. Series 94-H2O is formulated to meet especially stringent
VOC levels, making it ideal for use where strict environmental regulations are
enforced, such as the South Coast Air Quality Management District (SCAQMD) in California.
Hydro-Zinc uses a zinc dust which meets the requirements of ASTM D520 Type III and contains less than .002 percent lead by weight. “Essentially, all industrial coatings contain one or more inorganic pigments, which are minerals mined from the earth that may contain trace amounts of heavy metals,” Hansen acknowledged. “The inorganic pigments in a typical NSF Standard 61 certified two-component epoxy coating may contain more lead then Hydro-Zinc.”
Specifiers and owners also appreciate the competitive
pricing of Hydro-Zinc compared to a standard three-coat epoxy system. “Substituting
an organic zinc-rich primer at 2.5 to 3.5 mils dry film thickness (DFT) for an
epoxy primer at 3.0 to 5.0 mils DFT does not significantly raise the cost of
the interior coating system,” Hansen said. “Even if the cost of the coating did
rise slightly compared to an epoxy system, the impact on the cost of the
overall project including surface preparation and labor would be insignificant.
“We now have more than 10 years of case histories, performance testing and field evaluations by independent consultants, which attest to the long-term corrosion protection capabilities of Hydro-Zinc as part of a properly applied coating system in potable water tanks,” Hansen added. “Based on all of the available performance data, Hydro-Zinc represents an excellent choice for water tank fabrication shops and for subsequent use in the field after tank erection.”
ABOUT TNEMEC
Established in 1921, Tnemec is one of the largest privately
held companies in the U.S.,
specializing in industrial coatings for steel, concrete and other substrates
for new construction and maintenance. More than 120 architectural and
industrial coating products are manufactured at facilities in Kansas
City and Baltimore.
Headquartered in Kansas City, Tnemec operates
distribution facilities in Atlanta, Dallas, Denver, Houston, Indianapolis, New Orleans, Seattle and Compton, Calif.
In addition to the company’s national network of technical representatives,
Tnemec has technical representatives in Canada, the Dominican
Republic, England,
Puerto Rico and Trinidad. For more
information on Tnemec Company Inc. or any of its products, call 800-863-6321;
write to 6800 Corporate Drive,
Kansas City, Mo.
64120-1372; or visit www.tnemec.com.