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Check
before painting a metal roof
Most
people know about galvanic action, the corrosive effect
that occurs when incompatible metals come into contact.
But few people are aware of the damage to galvanised iron
gutters and downpipes that can occur when an old roof is
replaced with Zincalume, glazed tiles or painted metal
sheeting. These materials, unlike roofing of galvanised
steel, unglazed tiles or fibro, do not deposit metal salts
and minerals as a protective coating on the inside of the
gutter. Pure rainwater flowing from a chemically-inert
roof may wash away the protective film on the inside of
the galvanised guttering, causing rapid early gutter
failure.
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