Volumen II - SAM

Congreso SAM/CONAMET 2009 Buenos Aires, 19 al 23 de Octubre de 2009
COATINGS FOR THE SIMULTANEOUS PROTECTION
AGAINST STEEL CORROSION AND FIRE SPREADING
A. M. Pereyra, G. Canosa y C. A. Giudice
CIDEPINT (Centro de Investigación y Desarrollo en Tecnología de Pinturas),
calle 52 e/121 y 122, (1900) La Plata, Argentina
UTN (Universidad Tecnológica Nacional), calle 60 y 124, (1900) La Plata, Argentina
E-mail address: cagiudice@yahoo.com
SUMMARY
Flame retardant coatings with anticorrosive properties were formulated for protecting metallic structures of
buildings. Experimental coatings were based on a chlorinated alkyd resin prepared at laboratory and on
several pigments such as rutile titanium dioxide for improving hiding power, micaceous iron oxide for
controlling film permeability, zinc hydroxyphosphite for corrosion prevention and finally antimony trioxide,
zinc borate or trihydrated alumina alone or else a mixture among them for acting as fire retardant.
The inhibiting behavior was assessed in Salt Spray (Fog) Chamber and in 100% Relative Humidity Cabinet
while the fire retardant capacity was established by determining the limiting oxygen index (LOI) and flamespreading
value (Two Foot Tunnel).
The results show that micaceous iron oxide acts as an effective barrier since the film permeability
allows the requirements of rusting and blistering resistance to be made compatible, that antimony
trioxide has a synergistic action of in presence of chlorinated resins, that of zinc borate and trihydrated
alumina have an endothermic performance and finally that the highest PVC (inferior to the correspondent
CPVC) lead to a satisfactory efficiency due to the highest content of inorganic components in the coatings.
Key words: coating, rusting, blistering, limiting oxygen index, flame-spreading value.
1. INTRODUCTION
The conflagration develops powerfully exothermic chemical reactions of oxidation-reduction; the oxidizing
and the reducing are called combustive agent and combustible, respectively [1-3]. Under severe fire
conditions, conventional coatings and specially flame retardants generally do not have a significant action
[4]. In isolated fires or not too intense ones initiated by a cigarette, an electrical short-circuit, a spontaneous
combustion, coatings can increase fire spreading, show inertia or slight fireproofing characteristics or
decrease or extinguish the fire spreading. On the other hand, metallic substrates can suffer different
conditions of exposition: usual defects affecting the coating film promote the corrosion of the metal. The
most common protective system has an anticorrosive coating (one or two layers) in contact directly with the
metallic substrate adequately prepared and the finishing coating (also one or two layers) designed for
avoiding primer film damages. More complex systems can also include a shop primer if this product was
employed during the structure construction or else a wash primer if the metallic surface was previously
sandblasted or shotblasted as well as and intermediate coating applied on anticorrosive coat [5].
The objective of this paper was the formulation of the one coating system for the protection of metallic
substrates that simultaneously present adequate anticorrosive capacity and good flame-spreading resistance.
2. EXPERIMENTAL PROCEDURE
COATINGS FORMULATION. The composition percent in weight on solids is shown in Tables 1 and 2.
Pigmentation. The following pigments were selected:
- Micaceous iron oxide. The characteristics of this pigment are: Ferric oxide, 87.2%; silica, 5.1%; aluminum
oxide, 3.1%; magnesium oxide, 1.7%; calcium oxide, 0.9%; density, 4.8 g.cm -3 ; oil absorption, 11 g/100 g;
mean particle diameter, 65 m; at fine powder state presents metallic gray colour [6]. Microscopic
observation displays the lamellar shape of its particles, similar to mica. The properties of coatings prepared
with this pigment are fundamentally connected with its special particle shape and chemical inertness; when a
coating containing micaceous iron oxide is applied on a surface, the thin platelets orientate themselves
parallel to the substrate. Thus, the pigment provides a prevention action by barrier effect and besides helps to
binder protection from the degrading effect of sunlight.
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