It seems that mild steel electrical enclosures, no matter how well
> they are painted or coated, eventually rust away when they are mounted
> outdoors. The top surface usually goes first, which can't be seen from
> the ground when the box is high up, and the first we know is that the
> contents are ruined. So for some time we've been using the plastic
> ones, in particular those from CPC. These are expensive and tend to
> have minor defects. Sometimes the backplates don't fit the enclosures!
> Does anyone know of a solution to this problem? Plastic boxes that are
> well made and don't cost a fortune? Metal ones that don't rust? I
> priced up stainless steel ones but they are far too expensive.
>
> I'm talking here about enclosures in the size range 250x300x150 up to > 1000x800x250. >
> Bill
Cast iron is the answer, it was used for many years for electrical enclosures, but not by many manufacturers now, probably due to its weight disadvantage. It does have many good points though, it is resistant to corrosion, especially if painted correctly, and has an excellent appearance which blends into the building, unlike the modern alternatives which tend to stick out like a sore thumb.
One manufacturer who still uses C.I. is Lewden, check out their 'Weathertight' range:
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