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Galvanic Corrosion Rear rack


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I am in the process of designing a holder on the back of the Oli something a kin to what John E Davies did only using a Semi underbelly storage box for storing stuff.  I have the New style bicycle rack receiver on the back of my Oli.  I decided to pull of the bike rack receiver and it was full of water inside of the tube.  When I turned it upside down water came gushing out.  ie: the bottom half was water tight.  The old is now 1 year old, and has spent the last 3 months outside. (I just got my permit and engineered plans back from the county so I can start on a 3 sided RV port.)

The rack had only seen about a month of rain here, and what ever washing to had in the last year to fill the aluminum cavity with water.  For those that have a bike rack hitch.  You may want to check your rack.  If I was to keep the rack I would drill a couple of holes on the bottom to allow water out.  

Back to the subject.  This got me thinking about galvanic corrosion using SS bolts/washers/against the 6061-T6 aluminum.  It does not look like Oliver has done anything to offset the Galvanic corrosion.  Am I making to big of a deal about this?

What have other people done to mitigate the dissimilar metal?

Also I have some 7000 series aluminum lying around that I thought about using for backing plates.  I think that the Semi storage box is probably either 3000 or 5000 series, but I am just guessing. The structural aluminum I will uses will be 6061-T6.  Do you have to worry about Galvanic corrosion between differing series of Aluminum?

 

Early 1999 Ford F250 SD 7.3L Diesel 

2020 Elite II Twin -  Hull # 648

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Others may offer different opinions, but I don't typically worry about different aluminum alloys . My worry is fasteners (stainless) and separation.

There should be a drainway in every upright tube. Just a little hole, drilled near the bottom,  should suffice,  imo. Even good caps eventually leak. Water has to find a way out.

 

2008 Ram 1500 4 × 4

2008 Oliver Elite, Hull #12
 

 

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Stainless hardware and aluminum can cause issues, especially if you tow with corrosive deicers on the road 😳. I use aluminum antiseize liberally wherever stainless and aluminum touch, and it does help. While not ideal, SS fasteners are used everywhere on Ollies and mine seem to hold up OK. But I never tow in winter.

Permatex Anti-Seize Lubricant

I would not worry about different alloys, unless you plan to join them by welding. In that case they should match. I just had a major repair done on my rear cargo rack, which suffered cracks when I ran it into the decorative stonework of my house….. I added 1/4” reinforcements, and I just now reinstalled it to the cross beam with antiseize. There was no sign of corrosion at all when I removed the stainless hardware, after about three years.

EE829BD1-4396-4349-BE0E-D6A6911CE5CC.thumb.jpeg.9e4b710841824c178d882235cc7a5e37.jpeg

Note to self, do not back into buildings again. $50 for structural aluminum materials, six hours of my labor,  $150 welding labor, plus a $30 tip. …. I still haven’t addressed the stonework that got knocked off the house😤.

SeaDawg is correct, drain holes are needed everywhere, they don’t have to be large. even your entry steps need them, they trap water when stowed, it is unsightly and dumps on your sneakers when you open them. Trapped water for months and months OTH is really really bad news, road spray especially causes much worse problems, you must ensure it can’t happen. Have you contacted Oliver about your water? They might want to issue a service bulletin for drain holes.

You might find this amusing. …”Hmmmmmm, that is quite a lotta wattah!”

How to drain water from Touareg rockers 

John Davies

Spokane WA

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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags, Safari snorkel.

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That's why we have the clamshell drains, underbody.

Water, even condensate, has to have a way out.

Occasionally,  in humid, rainy spring weather, I see drips from the clams. I know they are doing the job.

As far as the step, I'm not (yet) worried about drain holes. In use, no issues. Tucked away, folded up, i get some leaf debris , but easy to clear away . Even if I  had drain holes, the leaves would stick.

John e Davies is correct.  Separate aluminum and stainless with a good washer/barrier/product.

Stainless bolts are weaker (long run)  than steel, but less corrosive with aluminum.  Stainless is less likely to react with aluminum than mild steel.  Aluminum fasteners are too weak, so forget that choice, imo

Always watch for signs.

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2008 Ram 1500 4 × 4

2008 Oliver Elite, Hull #12
 

 

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One other comment, antiseize on stainless threads prevents the nut from welding itself (seizing) to the bolt. I had to remove the big 1/2” bumper main bolts to do a mod, one nut was seized solid and I had to literally snap the bolt with a 3/4” breaker bar.

John Davies

Spokane WA

  • Like 1

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags, Safari snorkel.

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  • 3 weeks later...
On 7/17/2021 at 7:53 PM, John E Davies said:

One other comment, antiseize on stainless threads prevents the nut from welding itself (seizing) to the bolt. I had to remove the big 1/2” bumper main bolts to do a mod, one nut was seized solid and I had to literally snap the bolt with a 3/4” breaker bar.

John Davies

Spokane WA

John,

I just received my aluminum for the frame, and was going to un-bolt the old receiver rack supports. From what you wrote, I decided to spray the bolts/nuts with penetrating oil and let it set overnight to hopefully advert some of the problems with the stainless bolts seizing.  I went out with a couple of 18" breaker bars to get the bolts off.  I was already thinking of what steal tubing I had to make a extension for the breaker bars.  The first nut I tried virtually had no pressure on it so I dropped back to a ratchet. I had to laugh,  I'm guessing that there was less than 25 in/lbs of torque on all of those those nuts.  I'm Fortunate that the receiver assembly just didn't fall off.

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Early 1999 Ford F250 SD 7.3L Diesel 

2020 Elite II Twin -  Hull # 648

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