[RE-wrenches] mixing aluminum and galvanized steel

[penobscotsolar at midmaine.com]

And I would agree with Ray's reply. We install on islands in Maine, the
Bahamas, Lesser Antilles, USVI and Mexico, almost always within 150 of the
ocean, and high quality stainless won't react negatively with aluminum, at
least compared to other metals. I have seen galvanized zinc fasteners
rusted in less than six months. We use the stainless grade designed to be
used underwater. It is costly (we use Manasquan Fastener) but worry free
as long as it is torqued correctly (not very much) and used with anti
seize. We had one bad experience where one of my guys tightened the nuts
on the ss anchors with a drill and deep socket. Bad idea....I believe the
bolt heated up and expanded and caused galling. Lesson learned.

Daryl DeJoy
NABCEP Certified PV installer
Penobscot Solar Design




> I haven't seen a reaction between Stainless and Aluminum, if its a high
> grade Stainless. Lower grade stainless still has magnetic properties, and
> will corrode.
> I think the freezing of fasteners you are referring to is actually the
> galling of the threads of the stainless. This isn't due to corrosion, but
> the deformation of the bolt threads from even slight over tightening.
> Anti-seize or other lubricant helps this problem.
> We also found SS hardware needs to be torqued at much lower torques than a
> zinc plated bolt.
> I agree Zinc plated bolts aren't a good idea near the ocean, but in dryer
> places, it is a stronger, more trouble free (no jamming) bolt.
>
> R. Walters
> ray at solarray.com
> Solar Engineer
>
>
>
>
> On Oct 5, 2011, at 4:08 PM, conrad geyser wrote:
>
>> My experience on the Northeast coast(salty sometimes) is that the
>> galvanizing helps protect all the metals in the system.  The zinc in the
>> most anodic metal on the chart and will help protect anything.  On the
>> contrary, the stainless and the aluminum do react and in the case of
>> fasteners, often freeze.
>>
>> Don't use zinc plated of course, just hot dipped.
>>
>> Conrad
>> Cotuit Solar
>>
>> From: re-wrenches-bounces at lists.re-wrenches.org
>> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of
>> Kristopher Schmid
>> Sent: Wednesday, October 05, 2011 12:45 PM
>> To: RE-wrenches
>> Subject: Re: [RE-wrenches] mixing aluminum and galvanized steel
>>
>> This is an amazingly timely post for me!  I was just thinking of asking
>> the same question since i have a couple of ground mount installs coming
>> up with concrete pillars/galvanized anchor bolts/aluminum channel base.
>> I notice that DPW for example specs galvanized pipes to be attached with
>> u-bolts to their aluminum racking in their LGM racks.
>>
>> Anxiously awaiting the collective wisdom...
>>
>> On Wed, Oct 5, 2011 at 11:23 AM, Jeff Yago <jryago at dtisolar.com> wrote:
>> For years we have used standard mounting racks like UniRac rails bolted
>> together with stainless-steel hardware.  On larger arrays this usually
>> means bolting their extruded aluminum module rails to galvanized 3” pipe
>> supports for ground mounted arrays.
>>
>> We have recently received several “flags” during the engineering review
>> process of our design documents on state funded projects stating all
>> bolted connections between aluminum and galvanized steel will require
>> neoprene washers to prevent corrosion.
>>
>> Any of you run into this requirement or have had any problems?  The only
>> issues we ever see with corrosion is mixing copper and aluminum such as
>> where somebody used wrong type module frame ground connectors.
>>
>> Jeff Yago
>>
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>>
>> --
>> Shine On!
>>
>> Kris Schmid
>> Legacy Solar, LLC
>> 864 Clam Falls Trail
>> Frederic, WI 54837
>> www.legacysolar.com
>> 715-653-4295
>> NABCEP Certified PV Installer
>> BSEE
>>
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