The Importance of Temporary Corrosion Protection for Structural Steel

Blog | February 14th, 2019

Although durable, tough as nails even, there’s a period in the life of a structural steel element where it’s vulnerable. Upon leaving a surface treatment process, the metal is naked and corrosion-susceptible. To prevent the newly treated part from rusting, the metal needs further treatment. It’s in need of a temporary coating, a layer of corrosion protecting oil or epoxy.

Sandblasting Protection 

When structural steels require a special finish, one that’s polished or burnished in some client-specified manner, it enters a blast finishing station. All’s good so far, but now a major issue is about to trip the process up, and the results could be ugly. On leaving the sandblasting machinery, the beam or sheet part looks appealing, but it quickly dulls. The oxygen in the atmosphere is reacting with the bare steel surface, and the alloy is corroding. One solution is to coat the structural steel in a varnish-like black oil, a liquid that acts as a corrosion barrier. Happily, there are other answers to this surface stripping dilemma.

All about Epoxies and Blast Primers

If black oils won’t do the job, there’s a range of possible material solutions available. Besides oils and greases, waxes and varnishing agents, there are purpose designed, corrosion-inhibiting primers and epoxies. A reactive primer performs effectively as an all-encompassing surface shield. Then there are magnesium-zinc paints, adhesive epoxies, lacquer-like primers, and plastic-based liners. There are even fillers, which seal fastener openings on structural steel building elements. Indeed, for every exposed and blasted surface feature, there’s a temporary corrosion protection solution at hand.

When to Apply the Coating

The service isn’t designed to last forever. But surface treatment processes do leave structural steel vulnerable. That period of vulnerability only occurs when the material is stored after the finishing process, when it’s in transit, or when it’s laying around on a construction site. All the same, during this unknown period of time, the surface of the alloy will corrode. Temporary corrosion protection, as a short-lived rust prevention strategy, is applied after sandblasting operations, and the coatings are only removed when the metal pieces are ready for a fabrication-related proceeding or for erection work. Applied onsite or back at the factory floor, the coating would interfere with welding activity.

After the temporary coating has been sprayed or painted, the structural steel is immune to the effects of atmospheric corrosion. Oxygen can’t reach the metal. Finally, ready for the fabrication shop and its erection team, special chemical compounds, sometimes loaded with caustic solvents, are used to remove the coating. From here, a permanent coating system is made available.

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