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instead of paint coatings, although this may incur increased cost.
The combination of metallic and paint coatings can provide very
long term durability in aggressive environments and an aesthetically
pleasing appearance.”
A typical protective paint system involves a primer coat, sealer,
undercoat, intermediate coat, and finish coat, the company says.
The Association for Materials Protection and Performance
(AMPP), formerly the Society for Protective Coatings, represents the
global community of corrosion and protective coatings professionals.
Members “are dedicated to advancing technical and practical
expertise in corrosion prevention and control,” with AMPP helping
to protect infrastructure and assets worldwide through member and
workforce education and credentialing, company accreditation,
technological innovation, and global standardization.
AMPP says the structural steel primer is the first consideration
when approaching a large steel coating project. The primer will both
protect against the effects of environmental exposure and provide a
better surface to which a topcoat can cling.
Because steel is made mostly of iron, it corrodes in the presence of
oxygen. Even the most benign, controlled interior service environ-
ments can be corrosive, says AMPP. To prevent that corrosion, owners
have two choices: Apply protective coatings to structural steel or
choose structural material made of rare and costly superalloys.
“While corrosion protection is the more important role structural
steel primers play, they also provide a better surface for topcoat
application,” AMPP says. “Reasons for choosing a topcoat can vary.
It might be to add even more corrosion protection or it could be
for aesthetics only. In any case, topcoats last much longer when
applied over primers. That’s because primers fill in surface defects
that might otherwise compromise topcoat adhesion.”
Tradeoffs confront asset owners at every turn. Generally, the
choice depends on how long an owner intends a coating system to
last and how much they’re willing to spend.
For instance, owners interested in long-term asset protection
often choose intense surface preparations. A well-prepared surface
reduces the risk of premature coating failure. And if an owner is
willing to go to the expense of a more involved surface preparation,
it’s worth a similar investment in a high-quality primer (and top-
coat). It’s expensive up-front, but the benefit is a coating system that
remains intact for decades.
On the opposite end of the spectrum, owners hoping to incur as
The Gordie Howe Bridge will link Windsor and Detroit. little up-front cost as possible are likely to choose a less stringent
Photo Credit: www.gordiehoweinternationalbridge.com surface preparation and a less costly primer, too. Less intense
surface prep can increase the risk of premature failure, though, and
since this route comes with a lower price tag, owners should expect
For structural steelwork, the paint film thickness is important for to recoat the asset more frequently, warns AMPP.
lasting protection. Greenkote, which makes anticorrosion metal coatings, recently
“Best results are obtained when coatings are applied in heated, announced a major expansion at its headquarters facility in Brook
enclosed workshops; units for bridge structures and building frame- Park, OH. The expansion comes in response to a surge in demand for
work can be coated in this manner before erection and additional corrosion protection on environmentally exposed metal fasteners
coats may be applied on site, where required,” says Serco. “Modern and hardware in a number of different industries, the company says.
coating facilities can automatically blast clean and prime steelwork “I don’t know if climate change may be a part of it, but we’re seeing
before departure to site. Where improved resistance to mechanical notable increases in anticorrosion coating orders for all kinds of
damage or better durability in certain environments is required, different metal parts that are exposed to the elements,” says Mark
coatings of non-ferrous metals such as zinc or aluminum can be used Gore, CEO. “The orders are coming from a range of sectors, including
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