Corroded bolts on post shoes with incised timber posts

[OldKettle]

Hi,
Last summer, I installed three 100x100 incised timber posts in post shoes, bolted to a patio, as part of an attached pergola.

I am in the process of installing a further post to extend the pergola, but upon inspection of the original posts I noticed that the bolts which tighten the show look quite corroded.

I have attached photos of the three shoes, showing the corrosion, and also a brand new shoe for comparison.

I am just wondering if that degree of corrosion should be expected, and whether the preservative in the wood might have exacerbated it.

Any thoughts would be much appreciated.

 

[JohnD]

I strongly recommend that you buy stainless nuts, bolts and washers to replace the BZP ones. You can buy small numbers on Ebay from companies like Kays.

for your metal shoes, I strongly recommend giving them a coat of oil-based metal preservative primer and gloss paint, preferably before fitting.

I do also soak the ends of my posts in spirit-based wood preserver (not stain) such as Cuprinol before assembly

it looks to me like water is running down the posts to soak the end and the shoe

p.s.
some shoes have spacers or ridges to hold the bottom of the posts off the metal plate. yours do not but you can put in a few stainless nuts or something to hold them off the water.

 

[Burnerman]

They are only cadmium plated.....go for stainless if you want to.
John

 

[JohnD]

I am in a coastal region, and always use stainless outdoors now. There is salt spray in the air and I have had M8 galvanised studding post fixings eaten through and break in the past.

I don't know how long it lasts inland if not painted