Aluminum stands and chemical reactions

bernie · October 15, 2002, 08:42 PM

I have an aluminum stand that I have used for about 10 years. My question revolves around the fact that it is is held together with steel bolts and nuts. If I remember correctly from high school, this will cause a Galvanic reaction, correct? Will this weaken the aluminum, the steel, or both. I really like the stand and was thinking about replacing all of the bolts to refurbish my stand. I know that stands are cheap and I will get many responses saying buy a new stand. I have and I like the old one better. Thanks for all the help.

Art Eatman · October 15, 2002, 09:27 PM

Easiest is to just pull a few of the bolts and look. Are the bolts rusty, below the nuts/washers? Is there sign of erosion around the edges of the holes in the aluminum?

If there's no notable rust or erosion, I wouldn't worry. Odds are, the aluminum will be okay.

The cheapest bolts/washers/nuts that I've seen are in the farm/ranch supply stores, where they sell stuff by the pound. It wouldn't hurt to move up to Grade 5, if you're doing any replacing.

If everything you inspect checks out okay, just squirt WD 40 on all of them. An alternative is one of the salt-water anti-corrosion sprays, probably available at a boat store.

If you replace bolts, use some grease on stuff during assembly...

Art

keano44 · October 15, 2002, 09:42 PM

What an interesting question. I have a homemade, welded aluminum climber that is nearly 20 years old. It has stainless steel 5/16" bolts, and has seen heavy use. The top half also doubles as the frame for a wheeled cart which has rolled out two deer, or a deer and a hog at a time, sometimes. Absolutely no signs of weakening aluminum or steel. Believe it or not, all the bolts are the original ones (I have never lost a bolt or nut setting the stand up in the dark, with ice cold fingers). I wouldn't trade my stand for any stand on the market today. It was designed (by my cousin) to be a rifle stand. He made major improvements to a popular climber available in the late seventies. I then further modified it to make it convertible; you sit facing the tree for gun hunting, but can reverse the top and bottom halves, and sit with your back to the tree for bow hunting. And, as I mentioned above, I built a wheeled attachment which transforms one half into a cart for hauling out your deer. Have used it many times while hunting public areas where ATV's are banned.

Navy joe · October 16, 2002, 12:08 AM

The aluminum would weaken, it is the anode in that reaction. Pull the bolts, inspect. If everything is ok, paint bolts and bolt holes then re-assemble.

scotjute · October 18, 2002, 07:56 AM

The aluminum will corrode to the steel when the two are touching and wet. The good part of the equation is that you only have a small amount of steel to a large amount of aluminum. The reaction will occur only when stand is wet and then at a slow pace. For example if you reversed the situation and had aluminum bolts and steel stand, the small amount of aluminum would be annodic to a large amount of steel, the reaction would occur still only when stand is wet, but at a fast pace during that time.
Anything you can to either prevent the contact joints from getting wet or else separating the two metal with di-electric (like black electrician's tape) would stop the reaction.
Doesn't sound like this will cause eminent failure, but it does bear inspecting from time to time.

Art Eatman · October 18, 2002, 10:14 AM

Yeah, the old "sacrificial anode" bit. Used in pipelines and ships' hulls. Also referred to as "cathodic protection".

A chunk of aluminum or magnesium attached to the pipe or hull will interact with soil or seawater and erode, leaving them intact. The chunk is the anode; as it erodes it will plate the cathode.

In some soils, it's used with steel electric-power poles, as well.

, Art

Dogjaw · October 18, 2002, 07:29 PM

Toss the carbon steel bolts and put in stainless steel. I used to work in a nuke power plant, and stainless was the only approved fastner for aluminum to aluminum connections.

bernie · October 20, 2002, 11:53 AM

Where can you get stainless hardware. It is not real common in small town Arkansas stores where I live.

Dogjaw · October 20, 2002, 05:03 PM

A lot of True Value stores carry them up here. Try McMaster-Carr. They're a huge mail order retailer for all kinds of hardware and supplies.

They're at http://www.mcmaster.com Go to page 2914.

Art Eatman · October 20, 2002, 10:40 PM

Most hardware-store bolts are Cadmium-plated, so if you're not near saltwater they last many years. Heck, smear a little axle grease on'em when you install, and just check every three or five years.

, Art

October 15, 2002, 08:42 PM	#1
bernie Senior Member Join Date: September 12, 2000 Posts: 145	Aluminum stands and chemical reactions I have an aluminum stand that I have used for about 10 years. My question revolves around the fact that it is is held together with steel bolts and nuts. If I remember correctly from high school, this will cause a Galvanic reaction, correct? Will this weaken the aluminum, the steel, or both. I really like the stand and was thinking about replacing all of the bolts to refurbish my stand. I know that stands are cheap and I will get many responses saying buy a new stand. I have and I like the old one better. Thanks for all the help.

October 15, 2002, 09:42 PM	#3
keano44 Senior Member Join Date: June 12, 2001 Location: Lafayette LA Posts: 177	What an interesting question. I have a homemade, welded aluminum climber that is nearly 20 years old. It has stainless steel 5/16" bolts, and has seen heavy use. The top half also doubles as the frame for a wheeled cart which has rolled out two deer, or a deer and a hog at a time, sometimes. Absolutely no signs of weakening aluminum or steel. Believe it or not, all the bolts are the original ones (I have never lost a bolt or nut setting the stand up in the dark, with ice cold fingers). I wouldn't trade my stand for any stand on the market today. It was designed (by my cousin) to be a rifle stand. He made major improvements to a popular climber available in the late seventies. I then further modified it to make it convertible; you sit facing the tree for gun hunting, but can reverse the top and bottom halves, and sit with your back to the tree for bow hunting. And, as I mentioned above, I built a wheeled attachment which transforms one half into a cart for hauling out your deer. Have used it many times while hunting public areas where ATV's are banned. __________________ I've seen good, and I've seen bad. I've seen fire, and I've seen rain. I've seen war, and I've seen peace. I've seen mountains, and I've seen desserts. I've seen the world, and thought I'd seen it all. But of all the scenes I've ever seen, I ain't never seen no scene, like the scene I'm seein now!........keano44

October 16, 2002, 12:08 AM	#4
Navy joe Senior Member Join Date: January 28, 2001 Location: VA, USA Posts: 1,804	The aluminum would weaken, it is the anode in that reaction. Pull the bolts, inspect. If everything is ok, paint bolts and bolt holes then re-assemble. __________________ FY47012

October 18, 2002, 07:29 PM	#7
Dogjaw Senior Member Join Date: October 6, 2001 Location: S.W. Michigan Posts: 560	Toss the carbon steel bolts and put in stainless steel. I used to work in a nuke power plant, and stainless was the only approved fastner for aluminum to aluminum connections. __________________ There are three kinds of men: 1) The ones that learn by reading. 2) The few who learn by observation. 3) The rest of them have to pee on the electric fence and find out for themselves..........

October 20, 2002, 05:03 PM	#9
Dogjaw Senior Member Join Date: October 6, 2001 Location: S.W. Michigan Posts: 560	A lot of True Value stores carry them up here. Try McMaster-Carr. They're a huge mail order retailer for all kinds of hardware and supplies. They're at http://www.mcmaster.com Go to page 2914. __________________ There are three kinds of men: 1) The ones that learn by reading. 2) The few who learn by observation. 3) The rest of them have to pee on the electric fence and find out for themselves..........

October 15, 2002, 09:27 PM	#2
Art Eatman Staff in Memoriam Join Date: November 13, 1998 Location: Terlingua, TX; Thomasville, GA Posts: 24,798	Easiest is to just pull a few of the bolts and look. Are the bolts rusty, below the nuts/washers? Is there sign of erosion around the edges of the holes in the aluminum? If there's no notable rust or erosion, I wouldn't worry. Odds are, the aluminum will be okay. The cheapest bolts/washers/nuts that I've seen are in the farm/ranch supply stores, where they sell stuff by the pound. It wouldn't hurt to move up to Grade 5, if you're doing any replacing. If everything you inspect checks out okay, just squirt WD 40 on all of them. An alternative is one of the salt-water anti-corrosion sprays, probably available at a boat store. If you replace bolts, use some grease on stuff during assembly... Art

October 18, 2002, 07:56 AM	#5
scotjute Senior Member Join Date: December 6, 2001 Location: texas Posts: 260	The aluminum will corrode to the steel when the two are touching and wet. The good part of the equation is that you only have a small amount of steel to a large amount of aluminum. The reaction will occur only when stand is wet and then at a slow pace. For example if you reversed the situation and had aluminum bolts and steel stand, the small amount of aluminum would be annodic to a large amount of steel, the reaction would occur still only when stand is wet, but at a fast pace during that time. Anything you can to either prevent the contact joints from getting wet or else separating the two metal with di-electric (like black electrician's tape) would stop the reaction. Doesn't sound like this will cause eminent failure, but it does bear inspecting from time to time.

October 18, 2002, 10:14 AM	#6
Art Eatman Staff in Memoriam Join Date: November 13, 1998 Location: Terlingua, TX; Thomasville, GA Posts: 24,798	Yeah, the old "sacrificial anode" bit. Used in pipelines and ships' hulls. Also referred to as "cathodic protection". A chunk of aluminum or magnesium attached to the pipe or hull will interact with soil or seawater and erode, leaving them intact. The chunk is the anode; as it erodes it will plate the cathode. In some soils, it's used with steel electric-power poles, as well. , Art

October 20, 2002, 11:53 AM	#8
bernie Senior Member Join Date: September 12, 2000 Posts: 145	Where can you get stainless hardware. It is not real common in small town Arkansas stores where I live.

October 20, 2002, 10:40 PM	#10
Art Eatman Staff in Memoriam Join Date: November 13, 1998 Location: Terlingua, TX; Thomasville, GA Posts: 24,798	Most hardware-store bolts are Cadmium-plated, so if you're not near saltwater they last many years. Heck, smear a little axle grease on'em when you install, and just check every three or five years. , Art