PV Expansion - Wall Mounted Experimentation

[AE-NMidlands]

I wouldn't give a worry to galvanic corrosion and I'd use s/s fasteners for ease of disassembly.

I certainly would worry! Some friends made an all-weather table-top display board of plastic sheets bolted down to a mild steel frame (into tapped holes...) They were surprised to see the stainless bolts go rusty, and even more surprised when a few weeks later they found they could pull the bolts out by hand! The stainless bolts had wasted (waisted?) at the contact and lost about 50% of their diameter. I did have one but can't find it to take a pic at the moment.
I would use galvanised bolts into the steel, or use plastic top hat washers to keep the metals apart.
A

[Joeboy]

I wouldn't give a worry to galvanic corrosion and I'd use s/s fasteners for ease of disassembly.

I certainly would worry! Some friends made an all-weather table-top display board of plastic sheets bolted down to a mild steel frame (into tapped holes...) They were surprised to see the stainless bolts go rusty, and even more surprised when a few weeks later they found they could pull the bolts out by hand! The stainless bolts had wasted (waisted?) at the contact and lost about 50% of their diameter. I did have one but can't find it to take a pic at the moment.
I would use galvanised bolts into the steel, or use plastic top hat washers to keep the metals apart.
A

I would wonder if there was something project specific in that or flawed material? Never seen anything that extreme in.30 years of working with carbon steel, stainless steel, titanium, various alloys and aluminium in saltwater and out and with various ground fault conditions. Stainless bolts (316) don't go rusty. Sometime ferrous dust clings due to say an oil coating and can look that way. One I'll remember though. Still willing to learn.

Also that's stainless giving to steel which doesn't make sense? We are talking stainless giving to.aluminium which would be the other way around with the aluminium giving to the stainless but put a small magnesium anode in situ and its a protective visual indicator.

[AE-NMidlands]

I wouldn't give a worry to galvanic corrosion and I'd use s/s fasteners for ease of disassembly.

I certainly would worry! Some friends made an all-weather table-top display board of plastic sheets bolted down to a mild steel frame (into tapped holes...) They were surprised to see the stainless bolts go rusty, and even more surprised when a few weeks later they found they could pull the bolts out by hand! The stainless bolts had wasted (waisted?) at the contact and lost about 50% of their diameter. I did have one but can't find it to take a pic at the moment.
I would use galvanised bolts into the steel, or use plastic top hat washers to keep the metals apart.
A

I would wonder if there was something project specific in that or flawed material? Never seen anything that extreme in.30 years of working with carbon steel, stainless steel, titanium, various alloys and aluminium in saltwater and out and with various ground fault conditions. Stainless bolts (316) don't go rusty. Sometime ferrous dust clings due to say an oil coating and can look that way. One I'll remember though. Still willing to learn.

"Stainless" is better described by the French name "Inoxydable" - aka Inox. If you want it to survive in a reducing environment you need a different "stainless" chemistry altogether. We have a deeply pitted table fork from when it went through the compost heap (which isn't all aerated, although it should really be.)
You will still get a galvanic cell between "stainless" and another metal if there is moisture to provide the electrolyte.
(btw, what are the hollow boxes in addition to thew black bars against the stainless alloys? )

[Joeboy]

I certainly would worry! Some friends made an all-weather table-top display board of plastic sheets bolted down to a mild steel frame (into tapped holes...) They were surprised to see the stainless bolts go rusty, and even more surprised when a few weeks later they found they could pull the bolts out by hand! The stainless bolts had wasted (waisted?) at the contact and lost about 50% of their diameter. I did have one but can't find it to take a pic at the moment.
I would use galvanised bolts into the steel, or use plastic top hat washers to keep the metals apart.
A

I would wonder if there was something project specific in that or flawed material? Never seen anything that extreme in.30 years of working with carbon steel, stainless steel, titanium, various alloys and aluminium in saltwater and out and with various ground fault conditions. Stainless bolts (316) don't go rusty. Sometime ferrous dust clings due to say an oil coating and can look that way. One I'll remember though. Still willing to learn.

"Stainless" is better described by the French name "Inoxydable" - aka Inox. If you want it to survive in a reducing environment you need a different "stainless" chemistry altogether. We have a deeply pitted table fork from when it went through the compost heap (which isn't all aerated, although it should really be.)
You will still get a galvanic cell between "stainless" and another metal if there is moisture to provide the electrolyte.
(btw, what are the hollow boxes in addition to thew black bars against the stainless alloys? )

We live and learn, most fixing kits for solar are aluminium in nature, bare or anodised with some stainless steel fittings which have direct contact with the aluminium. I stand by what I said. This is not something to worry about.

On the blank.boxes, no idea!

[Joeboy]

Although in saying the above I have handmade mounting brackets for my sons PV install from mild steel base and I ensured multiple 100% cover layers of paint and a long cure time. Paint systems themselves can.have a big.impact as can.a coating of grease.

These thoughts are from a saltwater 4,500V AC with a few hundred Vdc dotted around background and observation so not directly comparable to freshwater LV. Should work though. Fingers .

[Marcus]

Iirc from my boat days you need 316 stainless for marine applications not 304 (the other common stainless). In marine environment 304 will corrode, 316 won't.

Again iirc, you can mix 316 stainless, galv and aluminium without major issues, but mixing with mild steel encourages galvanic corrosion.

I've used unistrut (univolt) for my barn pv arrays and so-far so-good, but the main potential issue is that it's mostly electroplated galv rather than the hot-dipped you get on boat fittings. There's nothing intrinsically wrong with electroplated, but it depends on if they put down a good layer of zinc or skimped on it - it's hard to tell until it starts rusting.

[Stinsy]

Iirc from my boat days you need 316 stainless for marine applications not 304 (the other common stainless). In marine environment 304 will corrode, 316 won't.

Again iirc, you can mix 316 stainless, galv and aluminium without major issues, but mixing with mild steel encourages galvanic corrosion.

I've used unistrut (univolt) for my barn pv arrays and so-far so-good, but the main potential issue is that it's mostly electroplated galv rather than the hot-dipped you get on boat fittings. There's nothing intrinsically wrong with electroplated, but it depends on if they put down a good layer of zinc or skimped on it - it's hard to tell until it starts rusting.

They do both electroplated and hot-dipped unistrut. (I think you can get stainless too).

[chris_n]

Iirc from my boat days you need 316 stainless for marine applications not 304 (the other common stainless). In marine environment 304 will corrode, 316 won't.

Again iirc, you can mix 316 stainless, galv and aluminium without major issues, but mixing with mild steel encourages galvanic corrosion.

I've used unistrut (univolt) for my barn pv arrays and so-far so-good, but the main potential issue is that it's mostly electroplated galv rather than the hot-dipped you get on boat fittings. There's nothing intrinsically wrong with electroplated, but it depends on if they put down a good layer of zinc or skimped on it - it's hard to tell until it starts rusting.

They do both electroplated and hot-dipped unistrut. (I think you can get stainless too).

You certainly can get stainless unistrut, we used to use in for some applications (can't remember why now). I believe it is used in the food industry.

[Marcus]

Iirc from my boat days you need 316 stainless for marine applications not 304 (the other common stainless). In marine environment 304 will corrode, 316 won't.

Again iirc, you can mix 316 stainless, galv and aluminium without major issues, but mixing with mild steel encourages galvanic corrosion.

I've used unistrut (univolt) for my barn pv arrays and so-far so-good, but the main potential issue is that it's mostly electroplated galv rather than the hot-dipped you get on boat fittings. There's nothing intrinsically wrong with electroplated, but it depends on if they put down a good layer of zinc or skimped on it - it's hard to tell until it starts rusting.

They do both electroplated and hot-dipped unistrut. (I think you can get stainless too).

You certainly can get stainless unistrut, we used to use in for some applications (can't remember why now). I believe it is used in the food industry.

That does make sense - for the food industry. I do wonder though, wether using ss unistrut would be any cheaper than actual pv rail systems.

I seem to recall reading (on here probably) that you can get hot-dipped, but i just went with what my local supplier had. Actually some of the small meccano bits to put the unistrut together are hot-dipped.

[AGT]

We used stainless steel unistrut offshore, it was the first time I saw double unistrut and it had to be cut by hand