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Rust on stainless steel solar panel mid-clamps. What's going on here?

Rust on stainless steel solar panel mid-clamps. What's going on here?

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  #1  
Old 10-03-19, 01:16 PM
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Rust on stainless steel solar panel mid-clamps. What's going on here?

Hey guys,

We had 2 ground mounted arrays erected just 3 months ago using Unirac's mounting system. I went back to the panels the other day to find that the mid-clamps were experiencing rust. According to Unirac, these clamps are supposed to be stainless steel. I am confused as to why this is happening and if it's just surface rust or if the integrity of the bolts/nuts are compromised.

I know stainless steel can be susceptible to corrosion if scratched so maybe this happened when the bolts were torqued down (most are experiencing corrosion beneath nut)? We aren't experiencing this sort of rust on any of the end clamps though.

Please see the attached pictures and let me know if you guys think I should be concerned and/or have the installer replace all of them (56 panels in total so they would have to disassemble the entire arrays). I am also worried that if it continues, it will leave rust stains on the panels. The stainless steel must be of the ferritic variety because as seen in the pictures, the metal is magnetic.

Thank you very much for your help!

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Last edited by PJmax; 10-03-19 at 09:06 PM. Reason: cropped/resized pictures
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  #2  
Old 10-03-19, 01:27 PM
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I would suspect that it's a galvanic reaction between dissimilar metals. One of your nuts says 304, that is the type of stainless used. You would have to direct your inquiry toward the installer, we have no way of knowing what any of the other parts are made of. But I would hazard to guess that something there isn't 304.
 
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Old 10-03-19, 01:47 PM
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Gotcha, in your opinion, is this something I should be concerned about or is it just aesthetic? The plate that the bolt goes through is considerably more magnetic than the bolt itself and subsequently experiencing more rust (especially where the nut contacts the plate like you said).
 
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Old 10-03-19, 02:54 PM
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Don't know. Depends if those plates are steel or not. Your installer should know. And if they are, i dont think they should be corroding like that, and yes, it will only get worse. But a nylon washer under the nut would isolate the nut.
 
Norm201 voted this post useful.
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Old 10-03-19, 03:58 PM
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I spoke with the manufacturer that said all components are either 302 or 304 stainless steel. I'm wondering if this is a defective batch.
 
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Old 10-03-19, 04:10 PM
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Stainless is not completely rust proof, depending on the grade, it's application, and it's compatibility with adjoining materials it is acceptable that some staining can occur.

302 and 304 are basically the same, I doubt you have a bad batch but what it's attached too is probably the likely culprit!
 
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Old 10-03-19, 04:40 PM
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That's the problem, the entire clamp assembly is stainless steel. The framing on the panels is aluminum. I don't see why this sort of rust would occur after only 3 months and in worry there will be permanent rust staining on the panels soon.

A neighbor has the same clamps with zero rust on them. What gives?
 
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Old 10-03-19, 09:09 PM
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Each member is allotted 10mb of picture storage. You were at 23mb with your pictures. Very important to resize them before posting them. 600x600 will yield a full page picture and be approx 75kb. I'be resized your pictures and you are currently at 500kb.

Your first picture was the only one really needed as it shows it all. I was looking at Uniracs site and they take everything very seriously. I would send them just your first picture and let them tell you what the deal is.
 
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Old 10-04-19, 04:26 AM
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The following are excerpted from various sources.

Yes, aluminum and stainless steel can and do corrode when put together. The two differing metals set up a galvanic couple (aka a small battery) and corrode. Add in some moisture and the reaction happens faster.

Steel and aluminum are relatively compatible, but if brass and steel contact, the steel will corrode because it is more anodic than the brass. ... The aluminum will also corrode where its exposed surface contacts the brass plate because brass is more cathodic.

Despite the dissimilar metals and risk of corrosion, stainless steel screws are the recommended fastener for aluminum panels.
 
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Old 10-04-19, 05:44 AM
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Personally from all the SS hardware we use in the shop that is nothing I would even give a second glance, just some surface rust, nothing to be concerned about!
 
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Old 10-04-19, 07:04 AM
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May be way off base here but when I look at your first picture it looks like the nut has a lock washer under it and that is what is rusting.
 
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Old 10-04-19, 09:04 AM
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Interesting observation. I tried looking closely and it doesnt look like there is a separate washer.
 
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Old 10-04-19, 09:19 AM
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Could be that it is part of the nut but made of spring steel so it rusts re: press fitted to the nut.

The rest of the rust marks may only be staining.
 
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Old 10-04-19, 09:19 AM
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If you go into the specs..... that is a washer/nut combination.
The washer has serrations for locking.
 
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Old 10-04-19, 05:39 PM
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So Unirac is sending out brand new clamps but I must say I am somewhat skeptical that they won't do the same thing if I have 36 of them that rusted on me...
 
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