Where the environment is deemed to be aggressive, additional corrosion protection measures to the metal deck soffit should be considered by the party responsible for the slab and/or overall building design, taking into account aesthetic as well as structural considerations.

Steel strip with thicker galvanised coatings of 350g/m² and up to 600g/m² is available, but difficult to obtain, subject to large minimum order quantities and still has limited periods to first maintenance.

For profiled steel sheeting used in composite floor construction these non-standard galvanised coatings, although available, do not necessarily provide a practical (as increased coating thickness prevents the use of thru-deck welding for shear studs) or economic way of increasing durability.

Other options that should be considered for extending life to first maintenance are:

• The addition of a suitable paint finish
• SMD offer an enhanced galvanised coating (High Durability) option for all floor deck products, R51HD, TR60HD and TR80HD. The HD zinc-based coating incorporates Magnesium and/or Aluminium to offer superior durability, up to 3 times that of the standard 275g/m² galvanised coating - Contact SMD Technical Team for further information.
• Utilise the deck as permanent formwork only with the slab designed as an RC slab taking no contribution from the deck. In this situation, any degradation of the metal deck will not affect the structural integrity. However, the metal deck soffit may require an additional coating for aesthetic reasons.

When using metal decking in aggressive environments, where water will be located on the slab surface (such as car parks), adequate waterproofing of the slab surface is required to prevent ingress of water through the slab to the upper surface of the deck.

More information refer:

• Refer to SMD High Durability Coating for more information
• Design Considerations when using steel deck construction for car parks
• Durability of Steel Deck Composite Floors
• Steel-framed car parks – Corus Construction & Industrial
• ECCS Publication No. 84 – Car Parks