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John Williamson · 23-06-2017, 10:22 PM posted to uk.rec.gardening

On 23/06/2017 21:25, wrote:
IME, aluminium glazing clips (w and z) beat stainless steel hands down. All it takes is a little scratch in the surface and ....

You have a scratched stainless steel clip. If it corrodes at the
scratch, it wasn't stainless steel, and was probably mild steel
passivated using nickel plating or similar.

Aluminium, on the other hand, gets brittle with age, in my experience.

OTOH, have a couple of lean-to "growhouses". These are made entirely of aluminium and are polycarbonate glazed. I need to replace the poly panels but, to do so, need to unscrew fixings between the alu struts. I have tried everything I can think of from WD40 thru all sorts of "professional" things. I cannot shift a single screw. So I wonder if the "non-corroding" properties of aluminium are what they're made out to be!

Using steel screws in aluminium will lead to corrosion of the aluminium
inside the screw hole, which causes it to expand and make the screws
seize solid. That's if the aluminium doesn't dissolve round the screw,
letting it fall out.

They are not easy to extract...

I'd recommend using aluminium pop rivets when you re-glaze it, and
resign yourself to drilling them out next time it needs re-glazing.

--
Tciao for Now!

John.