What type of steel fasteners for aluminum?

[Sigi]

Quick question. I ordered some stainless steel bolts, washer and nuts to mount tailgate, C pillar and cover the armor mounting holes. But after reading up on it, it looks like stainless would do more harm than good on aluminum. What type of surface coating should I look for instead? What is the factory using? Thanks in advance

 

[Mogman]

Every bolt/nut I have seen in the HMMWV body is good ol steel, steel seems to hold paint better than stainless, just make sure to paint any bolts, nuts etc.
Edit, don't think you are going to hurt anything by using stainless unless you store/use the truck in an environment that promotes corrosion.

 

[Coug]

Zinc plated steel bolts are probably your best choice.
The zinc acts as a sacrificial barrier between the two metals.
Also add anti seize whenever possible.
I also do a layer of 20 mil PVC tape on any bare metal surfaces between the two metals. If the surfaces are painted I don't really worry about them.

Orbit 2 in. x 50 ft. 20 Mil Pipe Wrap Duct Tape 53550 - The Home Depot

Seal your piping with Orbit 2 in. x 50 ft. Pipe Wrap Tape. This PVC tape helps prevent corrosion and can be used with metal pipe or conduit in pressure-sensitive applications.

www.homedepot.com

 

[mgFray]

All of the bolts that I've looked up the specs for have been either chromed or zinc coated. (Zinc is far cheaper and easier to source!). So ya, go with good old fashion zinc bolts.

 

[Action]

OEM are cadmium coated.

 

[TOBASH]

The Galvanic effect between stainless steel and aluminum would be negligible. You can always get aluminum screws.

 

[Action]

I tried 3 stainless 1/5” bolts in a cowl. The corrosion spread on the body about 3/4” from each bolt.

 

[TOBASH]

I tried 3 stainless 1/5” bolts in a cowl. The corrosion spread on the body about 3/4” from each bolt.

What grade stainless did you use? I guess the screws were perhaps lower in chromium content. There are different grades. Stainless I use in surgery is much less corrosion sensitive to many commercial applications.

The OP is mounting to Aluminum and Steel surfaces. There will be some corrosion issues. Anti-seize is a must.

There are Aluminum screws available. If the alloy in the screws is close things should be OK with the Aluminum surfaces. The steel might have issues. I noticed when I placed my airlift that some areas like the body mounts are isolated by plastic so I assumed it’s about corrosion.

There are metal laser devices to identify metals and the alloy percentages. They help explain corrosion issues.

 

[kendelrio]

There will be some corrosion issues. Anti-seize is a must.

Something to consider when applying anti-seize:

I work subsea offshore in an environment VERY conducive to corrosion. We use aluminum and stainless together.

One of the things we do to combat corrosion is anodes near the hardware; which isn't practical and would do nothing above water.

As far as anti-seize: if you use "Nevr-Seize" or any other metal based anti-seize, you're adding copper or nickel to the mix of steel and aluminum, which I know for a fact will corrode and basically cement your bolts in place. In our highly corrosive environment out here, we use this on all of our bolts to ensure we aren't having to drill and tap broken bolts out:

 

[Coug]

for anti-seize my preference is the Jet-Lube Marine Anti Seize.

It's non-metallic. Nicest thing I've found is it's a LOT easier to clean up than the metallic ones (especially an old can of nickel anti-seize I used to have) but stays in the threads and whatnot.

Marine Grade Anti-Seize Nonmetallic Anti-Seize & Thread Lubricant |…

 

[Sigi]

Don't know why I thought stainless would be the answer. I remember stainless screws causing the paint to lift for inches on a aluminum radar arch on a saltwater boat.

Good news is that I did not see any corrosion between OEM fasteners and the truck body. Maybe the truck spent most of its time in the desert.

Based on your feedback I'll use coated steel fasteners and make sure there is primer/paint around all holes. Maybe use plastic washers for non structural areas such covering up the armor plate holes. Thanks for the feedback.

 

[Retiredwarhorses]

Today, All bolts on the HMMWV are Zinc-Aluminum coated Grade 8.