Re: Paint Failure on Outside Metal Roofs


Aidrian Bridgeman-Sutton <smokeandsteam@...>
 

<< But I'd guess that few
1937-design cars were showing much paint failure by 1941 (and remember
that not all 1937 designs were BUILT in that year).>>

I'm reluctant to pick nits with someone who knows as much as Tony
does, but 30-something years ago I helped paint a number of galvanised
house roofs.

Then experienced roof painters believed that a new tin roof needed a
year or two in the weather before the paint went on, otherwise
residues from the galvanising process would cause the paint to flake
and peel very quickly - possibly within a few months. We did one job
for a joker who thought he knew better and despite our best efforts
with brushes and soapy water the paint was coming off in some areas
within a couple of years.

As far as I know this need for weathering is still accepted wisdom
with conventional paint and while there are some fancy processes that
overcome these problems I don't think they were terribly common in the
steam age.

So, unless galvanised car roofs were aged before they were installed
or treated in some other way before the cars were painted, I can't
imagine that the flaking and peeling woudl be limited to a small
number of cars, but could be pretty widespread, especially as cars
will tend to experince movement and flexing which you wouldn't get in
a building.

That said, the effects of the flaking paint might not be terribly
visible if the roof had the usual coating of soot and cinders

Aidrian

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