Substrate and surface treatments are the backbone of joist and deck design for natatoriums, addressing the project’s primary concern: corrosion.
For joists, there are two prevailing corrosion-resistant treatment paths. In the first option, joists are bare steel, not receiving a factory primer. The fabricator is responsible for surface-preparation in accordance with the Society for Protective Coatings to ensure proper coating adhesion. The manufacturer or a reliable third party may do this. This may be SSPC-SP6 Commercial Blast Cleaning or SSPC-SP7 Brush-off Blast Cleaning. The second choice specifies the joists to receive a primer, affording time to install since they can sit on the job site with the protection of the primer. Using this method, it is important to verify the compatibility of the top coat with the primer. The painting manufacturer likely requires surface preparation SSPC standard for adhesion. Field-applied joists and deck should receive the same topcoat paint.
In a caustic environment, steel deck should be specified as G90, a thicker galvanization than a typical G60 substrate. As with joists, deck surface treatments vary, but the overarching goal is the same: a robust finish coating system to protect the steel.
The design specifications may call for powder coating as a solution. In this instance, the bare galvanized deck may require an SSPC-SP1 before receiving the powder coat. Powder coating is a process by which the already-fabricated steel deck is electrically charged. A dry paint is then statically applied in a powder form and baked.
A middle route is to have the finish topcoat applied in the field. The procedure may go as following: pre-treating the galvanized steel, then the deck manufacturer applies an oven-cured epoxy coil coat (primer) prior to shipping to the jobsite. In the field, one or more coats of a hydrophobic (designated for natatoriums) paint is applied by others—brands such as Tnemec and Sherwin Williams Macropoxy. Tnemec 115, for example, is a dryfall paint that is ideal for this environment and coats the perforations in the acoustical deck.