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Best finish to address corrosion of 356 alloy

We currently manufacture a railing post with die-cast base. This alloy is quite resistant to corrosion. A railing post base will typically come into contact with concrete or pressure treated wood. The recent formulation of pressure treated wood (ACQ)is quite nasty to aluminum. We are spec'ing a new 356 base and are concerned with corrosion characteristics. What is the most effective (vs economical) way to address this? i.e anodizing, plating, powder coating. There is precious little info I can find that will definitively rule out the need for some kind of coating on this alloy (we use the current die-cast part unfinished).

Bart Bremmers
Buyer - Toronto, ON, Canada
2007

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Dear Bart,
Because you are concerned more for the chemical resistance that a coating will offer, I would suggest epoxy powder as having the greatest resistance to chemicals. Many people will not agree with this as epoxy will chalk and may not aesthetically look as good after a few months of weathering. However,if what the finish appears to look like (the surface appears slightly whitish )is not so important then you will obtain the best results from this type of resin system.

Terry Hickling
Birmingham, United Kingdom
2007

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Thanks for the reply.
I am concerned with corrosion. Do you equate that with chemical resistance? I suppose they are related. Epoxy powder coat is too expensive. I wish I could find specifics for 356 when it comes into contact with cement or ACQ lumber.

Bart Bremmers
- Toronto, Ontario, Canada
2007