Steelwork Primer - Necessary preparation before the Intumescent Painter Starts
Posted on 6th May 2021
Steel Paint Primer
By Jon Townsend
Passive Fire Protection has rightfully seen an increased focus in attention over recent years (no prizes for guessing why!)... yet the emphasis much of the time appears to be with the PFP Contractor alone, and not those who impact their work. The shift in attention with contractors also appears to be with firestopping, with intumescent application seemingly in the shadows. Firestopping understandably has more interfaces, volume, cost, detailing and a requirement on more schemes, yet a lack in attention to correctly planning for intumescent can severely disrupt a project, months down the line.
We have witnessed this first-hand recently and are keen to raise awareness on the importance in preparing properly prior to even letting an intumescent package. The conversation needs to start when procuring the steelwork package.
All good intumescent applicators will ensure the paint systems are applied within the required environmental conditions and comply with the Wet Film loadings as stipulated by the paint manufacturers. Both can also easily be evidenced with QA records.
An important element to consider however relates to the condition of the steelwork primer before intumescent application begins. A compatibility check can be obtained by sending the primer data sheet to the intumescent paint manufacturer, and it is at this point where most contractors stop their due diligence. This however only confirms that the two products are compatible if applied in line with manufacturers guidelines. It is therefore vital that the steelwork contractor applies the primer to the conditions as stipulated in the primer data sheet, with the primer thickness/loadings being a key element of this. Dry Film Thickness Reports can be issued as evidence to confirm this, similar to the expectation of the intumescent paint contractor for their element of works.
An over application of primer can not only skew intumescent DFT readings but more importantly can cause intumescent systems to de-bond and flake from the steelwork as the example photographs below identify. Whilst we as a company undertake primer reading spot checks as part of our QA processes, these are only ‘random checks’ and do not negate the steelwork contractor’s responsibility for ensuring compliance to all steel sections on site.
Fireproof Steel Paint
It should also be noted that whilst the intumescent paint application has a substantial thickness, it will follow the profile of the substrate exactly, and subsequently show any imperfections that existed in the original surface. This should be a consideration if there are any areas of coated steelwork on show on a project. Pockmarks and corrugations in the steel caused by the removal of mill-scale will therefore still be evident, and it is essential that any areas of rusting or damaged primer (e.g., caused by welding, or slings) are repaired. These will need to be to a visual standard if exposed.
It is not uncommon for the Intumescent Paint Contractor to be issued such corrective works when they commence on site, yet this understandably results in increased costs and extended programme periods on site. Considering such items early on in a scheme can ensure they are captured in the steelwork contractors’ scope and ensure a more fruitful intumescent package further down the line.
Tagged as: Intumescent
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