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How to prepare galvanised steel for application of SC902

With the fire industry becoming ever more scrutinised each day, it is important that compliant application of intumescent coatings is achieved. As you may be aware, it has long been industry practice to apply the same rules to galvanised steelwork as to carbon steel.

However, research and testing conducted by Nullifire shows that in a fire situation, the presence of a galvanising layer can affect the fire resistance performance of the overlaying fire protection system – therefore it is important that those applying SC902 Intumescent Base Coat follow the outlined recommendations below.

Following testing in accordance with ETAG018 Part 2, here at Nullifire we can offer assurance that SC902 may be applied to galvanised steel, after the following surface preparation has been achieved.

New Galvanised Steel

  • The substrate should be thoroughly cleaned and degreased.
  • Abrade / Key surface using a minimum of 80’s grade sandpaper (taking care to ensure that the galvanising is not removed in the process)
  • Where the galvanising does not meet the requirements for the corrosion specification or the corrosion class is greater than C2, it may be necessary, to apply an approved primer to achieve the required anti corrosive protection based on the environment classification.
  • Apply Nullifire SC900 Series to the required DFT based on the Hp/A.

Aged Galvanised Steel

  • Thorough fresh water washing to remove soluble salts ideally high pressure washing, or normal pressure accompanied by stiff wire brushing, ensuring the substrate is free forms all forms of contamination,
  • Abrade / Key surface using a minimum of 80’s grade sandpaper (taking care to ensure that the galvanising is not removed in the process)
  • Where the galvanising does not meet the requirements for the corrosion specification or the corrosion class is greater than C2, it may be necessary, to apply an approved primer to achieve the required anti corrosive protection based on the environment classification.
  • Apply Nullifire SC900 Series to the required DFT based on the Hp/A.

For more information on preparing galvanised steel for SC902 application, please download NTN001 or  please contact a member of the team.