The corrosiveness of fluoride‐containing fire gases on selected steels

Combustion gases were produced from several cable-insulation materials in separate experiments conducted in a model fire chamber. These gases were then allowed to interact with stressed metal specimens, consisting for the most part of various stainless and hardened steels as well as of carbon steel and stainless steel sheet. Thereafter the samples as exposed were stored in a humid atmosphere. As expected, PVC combustion gases caused the cracking of spring steel and also extensive pitting corrosion of stainless steel. These results confirmed that test conditions conformed to real-life fires as observed in practice. The combustion gases deriving from fluorinated polymers were much less corrosive on stainless steel and provoked only slight pitting in isolated cases. The rate of corrosion damage on carbon steel was lower by more than an order of magnitude than in the case of PVC. However, stress corrosion of sensitized 18/8 stainless steel and spring steel was found to occur. Tests on the thermal degradation of the dluorinated polymer ‘Teflon’ FEP and ‘Tefzel’ confirmed their high stability. If one compares the behaviour of these fluoroplastics with that of PVC it can generally be concluded that, although the use of fluorinated insulation materials on cables might not altogether eliminate corrosion problems in the event of fire, it does constitute a realistic contribution to fire protection and to the reeducation of fire-related damage.