We use cookies to offer the best possible user experience on our website. We also use third-party cookies, to deliver personalised advertisement messages. By using our website you agree, that cookies can be saved on your device. Further information on the cookies used and on how to disable them can be found here.

How is a reactive protective system made?

Unprotected steel, if exposed to atmospheric agents, is subject to rust. This is why steel structures must be protected throughout their prescribed lifetime, or for the number of years that the structure, provided routine maintenance is carried out, is to be used for its intended purpose. A passive fire protection system using reactive paint must be compatible with the anti-corrosion or rust-proofing treatments prescribed according to the project and the type of exposure to chemical, physical or atmospheric agents.
There are a number of phases to the treatment
  • preparing the surface
  • preliminary treatment
  • intermediate adhesion treatment
  • fire-protection treatment
  • finishing treatment

Preparing the surface, preliminary treatment and intermediate adhesion treatment.
The surfaces of the steel structure to be protected may be of different types.
  • ROLLED STEEL: surfaces with calamine or rust
    • The raw steel supplied by the metal works is often covered with a layer of calamine, to prevent the iron oxidising. However, this layer is often compromised and therefore rust has to be dealt with. Before proceeding with any kind of varnish or paint, the surface must be prepared by sanding it down, brushing or any other process as required.
    • Only once the surface has been properly prepared can an anti-corrosion system be applied, consisting of Amotherm Steel Primer SB (alkyd zinc phosphate) for application in an urban and light industrial environment, or Amotherm Steel Primer Epoxi SB (epoxy zinc phosphate) for a marine or heavy industrial environment.
  • GALVANISED STEEL, surfaces with zinc bloom 
    • For galvanised steel it is necessary to check the state of the galvanisation that, after some months, may have deteriorated giving rise to numerous surface defects known generically as zinc bloom. Because these are capable of seriously compromising the quality and duration of any subsequent protective paint, the surface must be properly prepared as required.
    • Once the surface has been prepared, it is still necessary to use a primer that acts as an anchor between the galvanising and the reactive coating. We recommend using Amotherm Steel Primer WB (acrylic) in dry indoor environments, or Amotherm Steel Primer Epoxi SB (epoxy zinc phosphate) in other situations.
  • PAINTED STEEL, previously painted surfaces
    • When the steel has already been painted, a number of different actions can be taken, depending on the type of paint on the structure and its state of preservation. It is always necessary to check such paint meets the anti-corrosion requirements for the environment in which it is to be used, and if it is not, it must be removed. If the painted surface is in a good state of preservation, it is necessary to check with the manufacturer to confirm its compatibility with the reactive protective system. If it is not possible to check this, and if the painted surface has deteriorated, the surface must be properly prepared, which may involve the total or partial removal of the existing paint. 
    • If the paint has been partially or totally removed and the under-surface has been properly prepared, an anti-corrosion system can be applied consisting of Amotherm Steel Primer SB (alkyd zinc phosphate) for application in an urban and light industrial environment, or Amotherm Steel Primer Epoxi SB (epoxy zinc phosphate) for a marine or heavy industrial environment.
The fire-protection treatment
Reactive/intumescent systems must only be applied to properly prepared, compatible surfaces. We advise against applying the protective coating in unfavourable environmental conditions and to read the technical information provided by the manufacturer very carefully. The thickness of paint to be applied in order to achieve the required protection is obtained by applying multiple coats, ensuring the correct amount of time has elapsed between coats. The thickness achieved during application can be checked using a wet film micrometer or, once it has dried, using a digital micrometer.
The finishing treatment
The finishing treatment must take account not only of the aesthetic effect but also of the type of corrosion the surface will be exposed to in the environment of use. This means that in dry indoor environments you may omit the finishing treatment unless a particular aesthetic effect is required, but in outdoor and/or corrosive environments a suitable finishing treatment must be selected. The standard EN ISO 12944-2 classifies the different environments in term of their corrosiveness, as follows.
  • C1: very low 
  • C2: low
  • C3: medium
  • C4: high 
  • C5-I: very high industrial 
  • C5-M: very high marine
A finishing treatment is not obligatory for class C1. If such a treatment is required for aesthetic reasons, we recommend Amotherm Steel Top WB or Amotherm Steel Top SB depending on the type of protection chosen. For class C2 we recommend a solvent-based product with the relevant finishing coat Amotherm Steel Top SB. Classes C3 and C4 require a polyurethane finishing coat with higher climatic resistance, Amonn offers Amotherm Steel Top PU SB. We do not currently have finishing products available for classes C5-I and M, but we are working on special solutions for these environments too.
For more information on the recommended coatings download the table
Back to the list