Risk of corrosion of aluminium bi-fold doors fixed to steel joist

[Hastings]

Are there any special precautions to take when fitting an aluminium d/g 3 door bi-folds unit into an opening (2360x2200) that has an RSJ over it?

 

I expect to fit packers between the steel joist and the bifolds frame so they won't be directly touching each other but wonder if the fixings that connect the two will create enough of an electrical connection to cause the aluminium to corrode prematurely?

 

Environment is fairly high humidity (West coast Scotland) close to sea. Wind blown rain regularly contains salt. My 5-year-old timber front door handle and lock made of aluminium alloy and stainless steel parts is already showing signs of corrosion.

 

The bi-folds will be installed in an attached uninsulated, unlined, random rubble stone workshop/store. The opening currently has a temporary timber frame and OSB panel in place with new cement render finishing up against its outer top and side face edges. The new bifolds would be fitted in the same position.

[JohnMo]

1 hour ago, Hastings said:

My 5-year-old timber front door handle and lock made of aluminium alloy and stainless steel parts is already showing signs of corrosion.

Stainless steel and aluminium are not friends. Stainless steel causes aluminium to corrode. Stainless steel will be a very low grade or not stainless steel to show any corrosion.

 

Aluminium and carbon steel are pretty much ok together. They arexin friendly terms.

 

But you have bigger issue if the steel and aluminium are together in your case - you have a thermal bridge, this will heat heat quickly and likely cause a condensation issue.

 

You really need to think about how everything goes together and how you mitigate the bridge. A drawing of your thoughts will be way easier to understand.

[Hastings]

I wasn't going to worry about thermal bridging as it won't be a heated space.

[Hastings]

Never installed anything like this before and looking for advice on how to fix to the RSJ and to the vertical two sides which are very rough.

Thanks.

[IanR]

4 hours ago, Hastings said:

I expect to fit packers between the steel joist and the bifolds frame so they won't be directly touching each other but wonder if the fixings that connect the two will create enough of an electrical connection to cause the aluminium to corrode prematurely?

 

The RSJs are likely painted (and appear to be so in your image), and there's a likely gap between them and the Aluminium, so no chance of galvanic corrosion. The fixings will have a very small contact area, and you're unlikely to us an un-coated steel screw, as it will corrode anyway, so a coated screw (zinc passivate for instance) will stop any galvanic corrosion.

 

4 hours ago, Hastings said:

My 5-year-old timber front door handle and lock made of aluminium alloy and stainless steel parts is already showing signs of corrosion.

 

If it was galvanic corrosion it would be the aluminium corroding - as its the stainless, the spec of the stainless just isn't up to the environment.

Edited Thursday at 14:55 by IanR