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Appendix
53
6.5 Summary of BDH Information
Sheet on Identifying Corrosion by
CFCs
The presence of halogenated hydrocarbons in the com-
bustion air causes surface corrosion on affected met-
als. Particularly susceptible is the combustion chamber
and the heat exchanger surfaces (including stainless
steel) as well as the metal components in the flue
socket, flue pipe connections and in the chimney.
The halogen compounds present in the combustion air
produce highly corrosive hydrochloric acid in the flame
and in some cases - depending on the precise compo-
sition of the combustion air - hydrofluoric acid, both of
which accumulate in the boiler and remain active over
long periods.
In order to limit the damage, the source of the air con-
tamination must be located and sealed off. If this is not
possible, the combustion air must be drawn from an
alternative clean source.
Halogens can occur in the following locations:
Commercial and industrial sources
Dry cleaners Trichloroethylene, tetrachlo-
roethylene, fluorinated hydro-
carbons
Degreasing baths Perchloroethylene, trichlo-
roethylene, methyl chloroform
Printers Trichloroethylene
Hairdressers Aerosol spray propellants,
hydrocarbons containing fluo-
rine and chlorine (freons)
Sources in the home
Cleaning and
degreasing
agents
Perchloroethylene, methyl
chloroform, trichloroethylene,
methylene chloride, carbon
tetrachloride, hydrochloric
acid
Home workshops
Solvents and thin-
ners
Various chlorinated hydrocar-
bons
Spray cans Chlorofluorohydrocarbons
(freons)
Table 11
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