Aluminum or steel rivnuts

[Packer fan]

What kind of rivnuts are you guys using?

Aluminum, stainless, or steel?

I am thinking aluminum because of the bimetallic corrosion. But are they too soft.

Thanks

[JMan]

I've always used steel before and plan to use steel on my build once it arrives. I've never had an issue with rust on my other vehicles/projects.

[edwardb]

I use steel rivet nuts. Mostly these: https://www.mcmaster.com/#98560a561/=1ckxs3f. Agreed aluminum ones aren't nearly as strong or durable. I'm far from an expert regarding corrosion between dissimilar metals (as in know almost nothing...) but these are cad plated, if that helps. Plus, as I understand, corrosion requires some type of electrolyte, like water or salt. Not expecting either. Within any time period I'm concerned about, really don't think it's an issue.

[Jeff Kleiner]

I am thinking aluminum because of the bimetallic corrosion. But are they too soft.

Thanks

RE: corrosion of dissimilar metals...it's gonna' be a fact of life with these cars. We're attaching aluminum panels to a steel chassis. Steel rivets or aluminum rivets you've still got differing metals. Same with rivnuts---even if you use aluminum ones to fasten two aluminum panels together you're going to use a steel bolt.

Jeff

[NAZ]

I use aluminum and cad plated steel rivet nuts (and other fasteners) in a variety of metals and I give consideration to galvanic corrosion when combining dissimilar metals. Yes the aluminum ones are not as strong as the steel but are plenty strong enough for most anything you would mount on sheetmetal, especially aluminum sheetmetal. For aluminum I like to use the type of rivet nut designed with the serration on the flange (they are made for soft metals) as they have much more bite and resist spinning. For very thin aluminum I will use the rivet nuts designed for use in fiberglass as they spread the load over a much wider area and sometimes I'll even use a flat washer on the back side for even more support in soft materials.

As for galvanic corrosion with dissimilar metals -- yes it does happen. And it's good that you are thinking about things like this -- most folks wouldn't until they saw a problem. But you won't see steel rusting when combined with aluminum as the aluminum is the sacrificial anode not the steel. But the aluminum corrosion will tend to foul the steel threads unless they are cad or zinc plated making removal of the threaded piece difficult or even causing damage to both sets of threads.

[GoDadGo]

I used aluminum because of where I am located (The Deep Humid South); however, if I ever do a 2nd build I will use Stainless rivets instead.

Rivetsonline is my vendor of choice and below is the stainless link for pop rivets:

https://www.rivetsonline.com/open-en...teel-mandrel#1

They also have rivet-nuts and other cool stuff in stainless too.

[Packer fan]

Thanks all

[KegMechanic]

[QUOTE=GoDadGo;323287]I used aluminum because of where I am located (The Deep Humid South); however, if I ever do a 2nd build I will use Stainless rivets instead.

I would stay away from stainless rivets or rivnuts. The galvanic corrosion between stainless and aluminum can be bad in moist environments. The rivet will last forever, but the aluminum will quickly corrode.

[GoDadGo]

I would stay away from stainless rivets or rivnuts. The galvanic corrosion between stainless and aluminum can be bad in moist environments. The rivet will last forever, but the aluminum will quickly corrode.

Sorry Keg, but you are mistaken.

The use of Stainless & Aluminum falls lower on the galvanic corrosion quotient chart than Steel or Iron and can be viewed via the attached links. Also, Factory Five uses T-6061 aluminum for all of their panels which is considered to be a Marine Grade Aluminum so it is a higher grade than the aluminum used to create standard rivets and/or rivet nuts.

http://www.monarchmetal.com/blog/gal...ions-answered/

https://galvanizeit.org/design-and-f...als-in-contact

Though I am a Banker by trade (Commercial Loan Work Out Officer) and have slept at a Holiday Inn Express on several occasions, my formal education is in Naval Architecture so metallurgy and the use of dissimilar metals is rather important in the design and construction of marine vessels. For the record I became a banker because of earning potential, but my passion is still in the marine industry and offshore oil field arena which tends to have a lot of ups and downs which are driven by oil prices.

Again, sorry to send a correction, but you are mistaken.

Steve

NOTE: Disconnecting your battery when the vehicle is not in use will reduce the effects of electrolysis, thus reducing the galvanic corrosion effect as well.

[MPTech]

I used aluminum on most of my build and don't have any issues. Just had to be careful when pulling them, too hard and it pulled the threads, but they weren't destroyed. Most of the places i used them was only for holding and not structural (aluminum panels: under dash panel (I fab'd, front & rear elephant ears, radiator aluminum, mostly so these items could be easily removed). I also gave the bolts a light coat of anti-seize.

[Dave Howard]

The corrosion between two dissimilar metals is referred to as Galvanic Corrosion. There are a few different metals on the roadster build. If you are at all concerned, use the stainless rivnuts. Id stay away from aluminium due to the lower strength.

[Avalanche325]

Aluminum rivnuts are plenty strong enough for hanging our non-structural panels. In the real world, I have yet to hear of an FFR falling apart due to corrosion. So unless you live next door to Spongebob, it is not going to matter if you use AL or steel. I do live a the beach, and rust / corrosion happen quickly. I used aluminum myself.

A little off topic:
A word or two on stainless fasteners. I see some guys going stainless crazy thinking that stainless is just some magic kind of steel that doesn't rust. Don't use stainless fasteners where high strength is required. A general ballpark is that they are about 1/2 - 1/3 the strength of a grade 8 fastener. Keep that in mind when going all shiny shiny.

The big PITA with stainless fasteners is galling. If it doesn't have loc-tite, it should have anti-seize. That is a good rule for pretty much anything on a car.

[Hotyacht]

Sorry Keg, but you are mistaken.

The use of Stainless & Aluminum falls lower on the galvanic corrosion quotient chart than Steel or Iron and can be viewed via the attached links. Also, Factory Five uses T-6061 aluminum for all of their panels which is considered to be a Marine Grade Aluminum so it is a higher grade than the aluminum used to create standard rivets and/or rivet nuts.

http://www.monarchmetal.com/blog/gal...ions-answered/

https://galvanizeit.org/design-and-f...als-in-contact

Though I am a Banker by trade (Commercial Loan Work Out Officer) and have slept at a Holiday Inn Express on several occasions, my formal education is in Naval Architecture so metallurgy and the use of dissimilar metals is rather important in the design and construction of marine vessels. For the record I became a banker because of earning potential, but my passion is still in the marine industry and offshore oil field arena which tends to have a lot of ups and downs which are driven by oil prices.

Again, sorry to send a correction, but you are mistaken.

Steve

NOTE: Disconnecting your battery when the vehicle is not in use will reduce the effects of electrolysis, thus reducing the galvanic corrosion effect as well.

Well Steve,

I would beg to differ. I practice Naval Architecture and placing stainless next to aluminium, even 6000 series is a big no-no. I have seen plenty of examples of structural failure due to corrosion under stainless fittings. Whenever the two materials come together it is a problem and so normal practice is to insulate between the two using some sort of isolating washer or a paste formulated to provide insulation, so it important to keep this in mind. Also stainless steel (316 marine grade) will corrode away very rapidly if starved of oxygen, but this is unlikely to be an issue in an FFR build. Stainless fastenings are not really that strong, can be easily damaged by galling, and it does rust/corrode if not polished correctly, so it isn't a wonder material by any stretch. I don't have any stainless fastenings in my build.

You are however correct, and much smarter than I, in regards going and working in some other sector rather than the Marine Industry.

cheers, Brett.

[GoDadGo]

Well Steve,

You are however correct, and much smarter than I, in regards going and working in some other sector rather than the Marine Industry.

cheers, Brett.

It has come in handy (My Formal Education) when surveying supply and research vessels, tugs and other ocean going or even brown water floating collateral. Also, for our cars the rivet material is more a matter of preference since none of these cars are meant to operate on the high seas.

Kill the power when garaged and those pesky electrons won't be moving as fast don't you agree?

[NAZ]

Echo the advice on anti-seize and concur that while SS fasteners come in different materials and tensile strengths. The kind commonly used in automotive applications are not high strength fasteners. So if you're using the more common 18-8 SS fasteners because they look cool be advised that they are not high strength and cannot be heat treated like Grade-5 and Grade-8 fasteners can. They can be work hardened to gain some strength but will never equal a G-5 fastener. Not all stainless steel is created equal and you will find they fall into three different categories: austenitic, ferritic, and martensitic. Some can be heat treated, some are more corrosion resistant, and some are very weldable. The 300 series SS like what is commonly referred to as 18-8 will typically run around 75ksi tensile strength while martensitic SS fasteners may top out at around 180ksi. To give you some perspective, G-5 tensile strength is 120ksi while G-8 is 150ksi so there are high strength SS fasteners out there but unless you know your fastener strengths how will you choose the right one for the application?

Also, if you use stainless fasteners in any metal (including stainless steel) you should be using some form of anti-seize if you want to ever get them apart so you should do a bit of research to learn what type of anti-seize to use for the various applications you may have. Anti-seize is not a one-size fits all and is formulated for specific applications.

Car building can be fun and there is a lot to learn. It's usually better to learn from someone else than by your own mistakes. Of course that doesn't always prevent me from making a mistake. I'm still attending the school of hard knocks and many times that's simply because I don't know enough about a subject to even ask a question.

[flynntuna]

Great thread, I'm learning a lot.
Are there any high strength, like grade 8 steel rivenuts?

[NAZ]

Just something to consider:

When looking at the strength of a rivnut stop and think about what you are bolting on that thin sheetmetal that requires a high strength rivnut. I think if you do your own pull-out testing you'll find that the standard ALUMINUM rivet nut will be much stronger than the thin sheetmetal you are attaching it to. Cut out a square of aluminum you'll be adding a rivet nut (or rivet stud) to and screw it to a block of wood you can hold in a vise. Use whatever screw spacing similar to your application. Install an aluminum rivet nut and a long enough screw you can get a good grip on and do a pull test. I think what you'll find is that if the rivet nut is correctly installed the sheetmetal will deform or the nut will pull out before the rivet nut threads fail. If you are adding an element that has enough weight or applied force great enough to deform the sheetmetal do you really need a stronger nut or stronger structure?

[UnhipPopano]

I disagree with this from Steve from a couple of perspectives:

"It has come in handy (My Formal Education [Naval Architecture]) when surveying supply and research vessels, tugs and other ocean going or even brown water floating collateral. Also, for our cars the rivet material is more a matter of preference since none of these cars are meant to operate on the high seas."

First, corrosion is corrosion. Ship or car the problem and solutions are the same.

Second, Fiberglass was first used for boating and then applied to cars.

Third, the stress analysts of racking and pitching is directly applicable to cars. When we hear about "Stiffness" this is basically the same thing.

Forth, just like ships, cars are in constant motion and have no solid foundation.

Fifth, the same principal refereed to as the "Admirals Curve" applies to cars.

Now when we look at the selection of what metal to use for rivets or nuts and bolts, steel rivets on aluminum will rust. Steel bolts into aluminum without protection will rust. So if you like steel, you also better like rust.

And Brett, it is much more likely the impact of Congress that Steve is not employed in the Maritime industry than intelligence. For those not familiar with this part of history, at one time all ships navigating in US waters had to be US Flag Vessels. Then Congress changed the law and now any ship can operate in us waters. Almost overnight Navel Architects and Marine Engineers were looking for a new way to make a living.

[GoDadGo]

.

And Brett, it is much more likely the impact of Congress that Steve is not employed in the Maritime industry than intelligence.

Unhip,

Regarding This Thread:
I stated that I like a certain type of pop rivet that happens to be made of stainless steel because they corrode less.
https://www.fastenal.com/content/fed...0Corrosion.pdf

Regarding My Intelligence:
I guess I'm sort of like the fictional character "Forest Gump" and know that I'm not the smartest man, but I do know what Love is.
On One Income Since 1989, my kids have been put though private schools, my wife and daughters through college and Baby Go-Dad is now at U.L.L.

Regarding My Career Choice:
Mike Rowe Said It Better Than I Ever Could So Share This With Your Kids:
https://youtu.be/f7JIR76TSn4

Steve

[mikeinatlanta]

I'll do my normal throw a stick in the spokes. If you are truly wanting to do it right, then the only place you should be using rivnuts are in blind locations, and the only blind locations on the average FFR is in steel tube, so go with steel rivnuts into steel tube. If you need blind fastening on an aluminum panel skip the rivnuts and use nut plates. It will give you build the appearance of quality is deserves. Pure blind fastening in non-blind areas make any build look rushed.
nutplates.jpg
100_2798.JPG

[mikeinatlanta]

Way back in the day teaching composites, I made a battery out of plates of carbon fiber and 7075 separated with simple cheese cloth. I connected wires to the battery and ran them up to the wall clock (1.5V clock) and would use the running clock as a demonstration of the galvanic potential between carbon fiber and aluminum. I have no idea how long it lasted after I quit teaching.

[Fixit]

Uh... we're building cars here, not the next space-probe.

[rich grsc]

Uh... we're building cars here, not the next space-probe.

Absolutely!! This is more of a p-ssing contest post now.

[NAZ]

Mike, that's interesting -- didn't know carbon fiber had that potential. Carbon fiber composites are very popular on cars as are aluminum alloys and get combined when fabricating structures. Good info!

[Chris @ Forma]

First I don't think it makes a lot of difference which you use. We are not building production cars that need to endure 100's of hours of salt spray at elevated temperatures. Most of the fasteners that we are applying are not safety critical anyway. I would select rivnuts based on the installation tools that you are using as much as the application. We use a very expensive pneumatic puller (benefit of my other business) that applies just the correct amount of torque. We too buy from JayCee Supply and Rivet (www.rivetsonline.com). Our preference are zinc plated rivnuts. Cost effective, easy to install, not inclined to spin or gall the threads. We use prefer the L series as they have a slightly larger flange in case you don't drill a perfectly round hole as is prone to happen when hand drilling in an awkard position in relatively thin materials. Speaking of drilling we use 135 degree, 6 facet drills as they have less tendency to drill non round holes in thin materials. For application to soft materials such as fiberglass, we use Jacknuts also available from JayCee.

My education is in materials science and there seems to be a bit of a feud of corrosion that is all at least partially true. For our application, I wouldn't be overly concerned about it. Like your daily driver, keeping the car clean and dry will help a lot.

Chris

[mikeinatlanta]

Mike, that's interesting -- didn't know carbon fiber had that potential. Carbon fiber composites are very popular on cars as are aluminum alloys and get combined when fabricating structures. Good info!

Combining carbon and aluminum in a structural application is not wise. I know it happens a lot, but doing it correctly is critical to joint longevity. Take some of the carbon drive shafts on the market. Measure resistance between the ends and if it shows a short you have a guaranteed short life product. It can be made to work, but it's design and process critical. I would never buy a carbon/aluminum part unless decorative only.

Some may think using nut plates is over the top, and some just enjoy doing it right without compromise. We each enjoy the hobby for our own reasons and it's all good.

[mikeinatlanta]

Uh... we're building cars here, not the next space-probe.

That's funny coming from a guy who uses a lathe to make super sweet axle plugs. Looking forward to seeing a build from someone who would do that.
Attachment 85021

Edit: And don't get me started on that dolly. My goodness that thing is sweet. If you go to that much trouble for the dolly, what will you do to the car?

[erlihemi]

Well this is certainly an interesting thread. Having been the "guy" that had to test a bunch of those "sinking boats" and crawl through tanks to check zinc anodes, stray voltage, brittle fracture, ad nauseum, I find it interesting that the lowly rivnut has gotten so much attention with regards to galvanic corrosion yet few have mentioned proper application and installation of the rivnut itself. Primarily a poor application of the device despite which material is used or which material it is installed in. The fundamental cause of the discussion is because people are not happy with what is supplied by FFR in the kit. Improper compression or material depth in fiberglass. Soft aluminum threads that are not adequate for repetitive applications on maintenance areas. The list goes on of failure modes that will occur before galvanic corrosion strikes. Wash the car, keep it dry, and use a battery disconnect. And why waste time with stainless?

[Fixit]

That's funny coming from a guy who uses a lathe to make super sweet axle plugs. Looking forward to seeing a build from someone who would do that.
Attachment 85021

Edit: And don't get me started on that dolly. My goodness that thing is sweet. If you go to that much trouble for the dolly, what will you do to the car?

Thanks for the compliments on the dolly (It wasn't trouble on the dolly, it was maximum strength with minimum materials/effort (about 6hrs), with SAFETY paramount), and indulge me on the axle plugs (lightbulb went off, $6 of material, 10 minutes on the machine-tools, sticky problem solved).

At risk of alienating myself here... If you look around on some of these builds on here, there are those that (IMO) have lost focus as to the actual usage of the machines they are building. Are you building a show-car/trailer queen, a balls-out racecar, or a street-machine driver?
(When a thread gets into a pissing contest about galvanic reaction of a steel rivnut into an aluminum panel (on a car that will never be stressed to the limits of the fastener or subject to "annual" to where this may be an issue...)

[JimLev]

Well looks like the rivet thread has been beaten to death.

[mikeinatlanta]

Thanks for the compliments on the dolly (It wasn't trouble on the dolly, it was maximum strength with minimum materials/effort (about 6hrs), with SAFETY paramount), and indulge me on the axle plugs (lightbulb went off, $6 of material, 10 minutes on the machine-tools, sticky problem solved).

At risk of alienating myself here... If you look around on some of these builds on here, there are those that (IMO) have lost focus as to the actual usage of the machines they are building. Are you building a show-car/trailer queen, a balls-out racecar, or a street-machine driver?
(When a thread gets into a pissing contest about galvanic reaction of a steel rivnut into an aluminum panel (on a car that will never be stressed to the limits of the fastener or subject to "annual" to where this may be an issue...)

Some of us build for the pleasure of building. I'm about 10,000 hours into mine with no immediate plans on finishing. Someone is going to get one heck of a ride when I kick off and the widow sells it.

[edwardb]

Well looks like the rivet thread has been beaten to death.

It was dead a while ago. Too bad. Seemed like a reasonable question by the OP.

[mikeinatlanta]

Second, Fiberglass was first used for boating and then applied to cars.

I do believe the first use of fiberglass was as an insulator, first actual structural was early WWII on airplanes and produced by Owens Corning in coordination with American Cyanimid. If I remember correctly American Cyanimid was heavy into plywood and had a reinforced line called Plymetal. First structural fiberglass being Owens Corning glass and cyanimid resin.

I'm only pointing this out because some seem to take personal offense at the discussion on this thread and any disagreement within that discussion.

[Avalanche325]

Absolutely!! This is more of a p-ssing contest post now.

I heard that Space-X was launching an FFR to race the Tesla that is in orbit.