What bolts for securing treated pine bearers to galv steel stumps?

[Nickoh]

The time has come to refurbish our deck and of all things I'm struggling to find acceptable bolts for attaching  bearers to the new galv steel stumps. 

Original construction was treated pine bearers and stumps, which someone decided to fasten together using generic hot dip galvanised bolts. Have attached a pic of one of the more intact samples have removed so far. The new stumps are galvanised steel, and I can't for the life of me find appropriate bolts to join the bearers onto them. Previously I've used tech-shield bolts (last spare from previous project also attached) for joining galv and treated pine, as something compatible with both treated timber and steel, but while bunnings still sells treated pine screws,  I can't see any equivalent bolts anymore. Galv bolts compatible with posts and incompatible with treated pine, OR stainless bolts incompatible with galv posts but compatible with the pine. The only fasteners stocked that are compatible with both are batten screws.

I assume I have to be missing something obvious, since bunnings does sell every other part of the decking system. Would appreciate someone pointing me in the right direction. 

[JacobZ]

Hi @Nickoh,

A warm welcome to the Bunnings Workshop community, it is fantastic to have you with us.

The issue of premature corrosion when galvanised fixings are in contact with treated pine comes from the reaction between the copper in the treatment and the zinc in the galvanised coating.

For this reason, you would be better off using 304 Stainless Steel Cup Head Bolts in a suitable size to pass through your bearers and stumps.

Stainless steel does not contain zinc, so it will not corrode prematurely like galvanised bolts can when in contact with treated pine.

Let me know if you have any further questions.

Jacob

[Nickoh]

Hi Jacob,

Yes, familiar with the mechanism. Unfortunately stainless has the reverse problem of causing premature corrosion in galvanised steel. Looking for bolts (like the Zenith ones sold in every bunnings two years ago when I last did a treated pine-steel joint) that are compatible both with the pine bearers and galv steel posts.

[JacobZ]

Hi @Nickoh,

Yes, you're correct. Apologies, I hadn't considered the galvanic corrosion effect between the galvanised stumps and the stainless steel.

I believe the Tech Shield bolts are still available to Special Order; they are just not being kept in stock anymore. Please allow me to confirm this with our supplier, and I will get back to you as soon as I can.

Jacob

[Noyade]

Hi @Nickoh and @JacobZ 

How long a bolt are you after Nick?

How many?

I was one who snatched up a lot of the bolts you're holding when they went to clearance at Bunnings a few years back. I love walking around Bunnings looking at clearance stickers.

Buckets of them.

Happy to share. 

Let me know.

Cheers!

[Noyade]

Apologies in advance @Nickoh.

Looks like the longest I purchased was 100mm.

Too short I suspect?

Cheers.

[JacobZ]

Hi @Nickoh,

I've confirmed with ITW Proline, who are the supplier for these bolts, that they can still supply them, but you would have to special order them.

If you speak with your local store's Special Orders or Trade desk, they can get in touch with ITW Proline to get you a price and then order them for you.

There are M10 and M12 cup head bolts at 100mm long. If you quote the SKU number, which is BTC10100 for M10 and BTC12100 for M12, this will help them find the correct bolts.

Let me know if there is anything else I can assist with.

Jacob

[Nickoh]

Nice find! Too short for what I'm after but definitely appreciate the offer.