Dave,

Stainless steel would be overkill on the post base IMO. The z-max should be fine.

Riles

John agrees with Riles. J.

Either HDG (hot dip galvanized) or Z-Max are good levels of corrosion resistance. Standard G90 galvanized zinc is a low level of protection compared to HDG or Z-max.

Stainless steel is the most corrosion resistant finish available. Ocean-salt air environments and some treated lumber requires stainless steel. If your PT lumber is treated for ground contact CA-B 0.21 pcf, ACQ or CBA with more than 0.40 pcf level of chemical treatment, stainless steel is recommended. The higher levels of chemical treatment accelerate metal corrosion.

Always use the same type of metal or coated fasteners as the metal connectors. Dissimilar metals react and the PT wood acts as a catalyst.

The John Mon has used nothing but .40 pt lumber forever my local lumber yard will bring in nothing else. Never a problem with z max.

In fact my test block from the first pile of .40 acq with every fastenerI ever used in cca impaled in it including an alum baluster sank 1/4'' in the stuff shows No,0,nadda,nix like no damage at all to any of them. That block is still siting outside my shop after ghessss how long was that..5 years at least. J.

Hi, if you do not mind using stainless steel post base, even though it's expensive, it's best choice to anti-corrosion. HDG (Hot dipped galvanization) surface can also resist rust, it's often used on carbon steel material, which is cheaper.