Stainless steel fixings in aluminium brackets? Seems like you can...

[The Green's]

Can you use stainless screws into aluminium brackets, such as when mounting your solar panels onto some aluminium angle brackets? Does the risk of bimetallic corrosion outweigh the benefits of your screws not rusting?

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Stainless steel fasteners in aluminium plates or sheets are normally considered safe, whereas aluminium rivets or bolts holding stainless steel parts together is an unwise combination, as there is a practical risk of corrosion.

So from reading that it seems that using stainless self tappers to fix you solar panels to your aluminum angle brackets is fine.

Just don't use your drill/impact driver with those stainless steel fixings, they may as well be made of aluminum the way they snap!

I was recently "reminded" that I do have hand screwdrivers too

 

[Steve and Denise]

Have you been buying cheap Chinese screws again ? Stainless is quite soft.

 

[TinaLes]

Despite being told similar, I installed our large 200watt solar panel with 4 corner, & two side UPVC Brackets by drilling straight through ali sides of the solar panel, and then buying some decent sized SS Pan Head self taping screws.
Screwed in by hand, as they were just the right length.
No Rust, no Corrosion thus far after 2.5 years.
LES

 

[Silver-Fox]

If your fixing the Ali angle to the solar panel surround.
Why not just use pop rivets.

 

[Campervan_man]

You could always wet assemble with fasteners and sealant.

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[The Green's]

Steve and Denise My screws were reassuringly expensive thank you, as was my inappropriately used impact driver! Actually getting the pilot hole the right size was key.

Silver-Fox I wanted to be able to remove the panels, and using rivets would have prevented this. There is a raised lip down the side of the roof which meant I wouldn't have been able to get a drill in to take out the rivets. The panels are quite close to that lip, but using hex head screws I can get a spanner on them if required.

 

[Silver-Fox]

Steve and Denise My screws were reassuringly expensive thank you, as was my inappropriately used impact driver! Actually getting the pilot hole the right was important was key.

Silver-Fox I wanted to be able to remove the panels, and using rivets would have prevented this. There is a raised lip down the side of the roof which meant I wouldn't have been able to get a drill in to take out the rivets. The panels are quite close to that lip, but using hex head screws I can get a spanner on them if required.

I can see where your coming from.
But screwing into Ali tends to be a one time process.

Keep doing and you’ll lose the “thread”

 

[David and Sally]

What about using some copperslip on the screws to help isolate the two metals? Just an idea. No science behind it.

 

[sallylillian]

I still would not use SS fixings in aluminium externally unless using a Duralac a coating which eliminates the galvanic risk and is used by yacht riggers. Simple to apply like locktite.

 

[tonyidle]

I still would not use SS fixings in aluminium externally unless using a Duralac a coating which eliminates the galvanic risk and is used by yacht riggers. Simple to apply like locktite.

Yacht riggers are contending with the possibility of continual exposure to salt water. Roof mounted on a mh a fastener has a much easier life. Having said that I tap the holes in the panel to accept an M5 Allen head fastener. Tapping for this purpose can be done with the tap in a drill/driver at low speed. When I removed a panel from a van I was selling it had been on 4 years. It came off as though I had fitted it the day before. All I do to protect the fastening is spray the screw with white chain grease before assembly. I don't like self-tappers for anything if there's a better alternative. MS self-tappers are worse than stainless for corroding in aluminium.

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[SIFTA SAM]

For info:-

I fitted my 130 W solar panel about 7/8 years ago to my B544.
I used s/s self tappers to secure the aluminium frame of the solar panel to the aluminium brackets.
I have removed the panel twice and would have used the next size self tappers if the threads had been stripped.
I have found no evidence of corrosion during this period or when the panels were removed.
Will be doing my annual 'security' check next week.

 

[the1andonly]

Ok, whats wrong with using rivuts and ss machine screws/ bolts?
Apart from the "expense "

 

[IRHP]

What about using some copperslip on the screws to help isolate the two metals? Just an idea. No science behind it.

I don’t think that would work as it might conduct. There is a product called Duralac made for this purpose. Widely used on yacht rigging where stainless fittings are fitted to aluminium masts. You don’t need a lot but it’s expensive stuff.