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Technical Advisory Document TAD0016
On-Site Treatment of Boltheads
When off site Firetex coated steelwork has been erected, the boltheads and nuts will then in the majority of cases need to be coated with Firetex in order to provide the required level of fire protection.
Treatment of these will depend on the type of bolt, but for the most common types, the following are the recommended treatments, assuming in all cases that a solvent based Firetex material is being used :-
Galvanised steel (new or unweathered) and Zinc Plated:–
- Degrease using Envirogard W500 Degreaser.
- Apply Leighs L703 Mordant Wash to the boltheads/nuts and prevent this running on to the Firetex.
- Apply Firetex to the boltheads/nuts to the lowest thickness required on the two connecting elements eg column dft* 665 microns, beam dft 475 microns, apply 475 microns to the boltheads/nuts.
- Apply required sealercoat to correct dft.
Galvanised steel (weathered):-
- If zinc salts have started to form on the bolt/nut, it is recommended that these are not used and replaced with new but if these bolts are to be used, all salts must be removed by fresh water washing followed by degreasing using Envirogard W500 Degreaser.
- Apply Leighs L703 Mordant Wash to the boltheads/nuts and prevent this running on to the Firetex.
- Apply Firetex to the boltheads/nuts to the lowest thickness required on the two connecting elements eg column dft 665 microns, beam dft 475 microns, apply 475 microns to the boltheads/nuts.
- Apply required sealercoat to correct dft.
Sheridised steel:-
- Degrease using Envirogard W500 Degreaser.
- Apply Firetex to the boltheads/nuts to the lowest thickness required on the two connecting elements eg column dft 665 microns, beam dft 475 microns, apply 475 microns to the boltheads/nuts.
- Apply required sealercoat to correct dft.
Black Bolts:-
- Degrease using Envirogard W500 Degreaser.
- For use in dry, internal environments, no further treatment is required prior to application of the Firetex. For all other environments, apply Resistex L722 at a nominal dft of 50 microns.
- Apply Firetex to the boltheads/nuts to the lowest thickness required on the two connecting elements eg column dft 665 microns, beam dft 475 microns, apply 475 microns to the boltheads/nuts.
- Apply required sealercoat to correct dft.
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