The two floors of my deck rest on 100x100mm timber. They are nailed, and
I had galvanised plates to hold the whole thing together in case of
hurricanes etc. The building inspector seemed happy with what I have
done, but I'm not that happy.

http://i58.tinypic.com/1zcll5x.jpg

The galvanised plates have now rusted, and I was thinking of putting
stainless steel brackets under the deck, bolted through to a 50x90mm
stainless plate on the outside of the studs.
I have been told that stainless steel will corrode in the absence of air.
Is that true and does it matter? The galvanised plates lasted about 15
years. They are against treated timber.

"MattyF" wrote in message
...
The two floors of my deck rest on 100x100mm timber. They are nailed, and
I had galvanised plates to hold the whole thing together in case of
hurricanes etc. The building inspector seemed happy with what I have
done, but I'm not that happy.

http://i58.tinypic.com/1zcll5x.jpg

The galvanised plates have now rusted, and I was thinking of putting
stainless steel brackets under the deck, bolted through to a 50x90mm
stainless plate on the outside of the studs.
I have been told that stainless steel will corrode in the absence of air.
Is that true and does it matter? The galvanised plates lasted about 15
years. They are against treated timber.

Yes it will corrode in the absence of air but it's not a problem in your
case is it?

On Sat, 08 Mar 2014 08:41:09 +0000, harryagain wrote:

Yes it will corrode in the absence of air but it's not a problem in your
case is it?

The plates will be against the timber, thus an absence of air.
I wouldn't be concerned about it except that an engineer that I trust has
said there may be a problem. However I'm not having brass brackets!

On 08/03/2014 02:09, MattyF wrote:
The two floors of my deck rest on 100x100mm timber. They are nailed, and
I had galvanised plates to hold the whole thing together in case of
hurricanes etc. The building inspector seemed happy with what I have
done, but I'm not that happy.

http://i58.tinypic.com/1zcll5x.jpg

The galvanised plates have now rusted, and I was thinking of putting
stainless steel brackets under the deck, bolted through to a 50x90mm
stainless plate on the outside of the studs.
I have been told that stainless steel will corrode in the absence of air.
Is that true and does it matter? The galvanised plates lasted about 15
years. They are against treated timber.


If air is completely absent, it won't corrode, any more than ordinary
iron or steel would. What is necessary is that the oxygen levels must be
low enough for the chromium not to oxidise, creating the protective
coating that stops stainless steel from rusting, but there must still be
enough oxygen to allow rusting.

In practice, that is unlikely except in underwater applications, where
the water is not free to circulate, such as around yacht keel bolts. In
your application, there should be more than enough oxygen reaching the
steel to keep the protective chromium oxide coat intact, although, as
you are near a coast, I would be inclined to used 316 stainless steel
for its improved corrosion resistance.

Colin Bignell

On 08/03/2014 02:09, MattyF wrote:
The two floors of my deck rest on 100x100mm timber. They are nailed, and
I had galvanised plates to hold the whole thing together in case of
hurricanes etc. The building inspector seemed happy with what I have
done, but I'm not that happy.

http://i58.tinypic.com/1zcll5x.jpg

The galvanised plates have now rusted, and I was thinking of putting
stainless steel brackets under the deck, bolted through to a 50x90mm
stainless plate on the outside of the studs.
I have been told that stainless steel will corrode in the absence of air.
Is that true and does it matter? The galvanised plates lasted about 15
years. They are against treated timber.


Stainless steel comes in different grades, which I can't remember now,
and 1 grade will be better or last longer than another grade.
I used to work in the Nuclear industry and stainless steel was commonly
used. |So that tells you how long it will last

On Sat, 8 Mar 2014 02:09:03 +0000 (UTC), MattyF
wrote:

The two floors of my deck rest on 100x100mm timber. They are nailed, and
I had galvanised plates to hold the whole thing together in case of
hurricanes etc. The building inspector seemed happy with what I have
done, but I'm not that happy.

http://i58.tinypic.com/1zcll5x.jpg

The galvanised plates have now rusted, and I was thinking of putting
stainless steel brackets under the deck, bolted through to a 50x90mm
stainless plate on the outside of the studs.
I have been told that stainless steel will corrode in the absence of air.
Is that true and does it matter? The galvanised plates lasted about 15
years. They are against treated timber.

Is there anything else we ought to know about the timbers in question?
Some southern-hemisphere woods are - erme - interesting.

Nick

On Sat, 08 Mar 2014 12:43:07 +0000, Nightjar wrote:

If air is completely absent, it won't corrode, any more than ordinary
iron or steel would. What is necessary is that the oxygen levels must be
low enough for the chromium not to oxidise, creating the protective
coating that stops stainless steel from rusting, but there must still be
enough oxygen to allow rusting.

In practice, that is unlikely except in underwater applications, where
the water is not free to circulate, such as around yacht keel bolts. In
your application, there should be more than enough oxygen reaching the
steel to keep the protective chromium oxide coat intact, although, as
you are near a coast, I would be inclined to used 316 stainless steel
for its improved corrosion resistance.

I just remembered that the engineer makes multi-million dollar yachts. So
I will go ahead with stainless steel. I was wanting to paint the outside
white - I suppose that is OK?

On Sat, 08 Mar 2014 13:01:54 +0000, Nick Odell wrote:

Is there anything else we ought to know about the timbers in question?
Some southern-hemisphere woods are - erme - interesting.

The timber is Pinus Radiata. The upper bits are H3 treated (CCA) and the
lower bits are H4 treated (even more CCA I suppose). The galvanised steel
over the H4 has rusted very badly.

http://woodlandexport.com/index.php?
option=com_content&view=article&id=56&Itemid=59

On 08/03/2014 12:29, MattyF wrote:
On Sat, 08 Mar 2014 08:41:09 +0000, harryagain wrote:

Yes it will corrode in the absence of air but it's not a problem in your
case is it?

The plates will be against the timber, thus an absence of air...

Unless you are planning to keep the timbers permanently under water,
enough air will get to the steel to keep the surface film of chromium
oxide intact.

Colin Bignell