Stainless Steel fasteners can be a bad thing?

[Quickstep192]

I read that it can cause galvanic corrosion when using stainless steel hardware on steel parts of the car. Is this true?

I’m planning to re-install my antenna which requires some fasteners in the fender well. Since they’ll be exposed to the elements, I had fully planned to use stainless fasteners so they don’t rust.

Is this a bad idea?

[salayc]

https://www.pemnet.com/design_info/galvanic-corrosion/

[Lyle O]

Yes, there is that potential (corrosion would occur in the least noble metal, in your case, the steel fender perhaps?). But as long as you insulate the two materials with, say, a plastic washer, no electrolytic action would occur. If the stainless does not contact the carbon steel directly, no corrosion.

[911pcars]

Use anti-seize compound to protect both. Without it, the steel component will rust with or without the stainless fastener.

Sherwood

[Harpo]

When ever possible I replace my rusty fasteners with stainless steel

[john walker's workshop]

Beware ss on ss. Had to use a disc cutter many times to get the damn things loose. Bindage, gallage, seizeage.

[Quickstep192]

I don’t care so much about the fastener, but I don’t want to come back I five years and find a hole the size of the washer rusted into my fender well.

Sounds like the safest path is a steel fastener with never seize followed by a coat of undercoating.

[Lyle O]

One other thing to note is that if you are replacing nuts and bolts in the engine compartment, you should use normal carbon steel (with appropriate zinc, etc.). If you drop one in there, the SS ones do not stick to a magnet, and I hate the idea of a nut or bolt floating around free in there...

[911pcars]

For critical structural assemblies (internal engine, suspension, driveline, etc.), most stainless fasteners aren't as strong as regular or alloyed steel. However, there are high strength stainless fasteners available for their special properties..... but at a cost, e.g. Bumax Ultra.

If not for those critical areas, can use the typical grades of SS, but use anti-seize to reduce galling or seizing.

As Lyle O suggests, don't drop the SS versions. I bounced this M8 cam housing nut into a drain back tube. One of several black holes. Was very fortunate to locate and fish it out after rotating the engine so the tube was vertical. Block those engine openings. They attract loose and nearby smaller objects.



Some fastener material info here:
https://www.boltdepot.com/fastener-information/materials-and-grades/materials.aspx

Sherwood

[ClickClickBoom]

Three things needed for galvanic corrosion, 1&2 are metals of a different position on the periodic table and 3# an electrolyte, any h2o based liquid other than pure h2o qualifies. Stainless steel has a very specific range of uses, fasteners are even narrower in scope. The only stainless in my car or plane is a spoon or fork in my lunch bucket. A&P Mechanic for 30+ years, I hate stainless with a passion, it is the single most misused metal by amateur mechanics and fabricators around.
You want your fasteners to be either zinc or cad plated, and when they start to rust, the plating is consumed and needs to be replaced.
The best anticorrosion process is the one that excludes any electrolyte, paint, rubber undercoating, then various petroleum types of anti corrosive treatments.
Do your own research then show me scientific proof anything is in error.
Try ACF-50 for a start on unprotected surfaces. I have never found corrosion under an active coating of ACF-50.

[911pcars]

A YouTuber did a test on available rust inhibitors. This is the result after bare metal test samples were exposed to a non-scientific daily salt spray after 7 months.
https://youtu.be/R5LSxpoqcWo



Some products lasted longer than others. Regardless, a spray maintenance schedule appears to be required. Per the ACF website: "ACF-50's thin film acts like an "OFF SWITCH" for corrosion remaining effective for up to 24 months."

Ideally, you don't want threaded fasteners to corrode or rust. Good stainless does neither. Powder coating good for selected applications (not fasteners). Metal conversion coatings (e.g zinc and CAD)are better than sprays. Ceramic coatings, even better. Try bare ferrous fasteners in your marine craft?

Sherwood

[Bigtoe32067]

Just use a rubber or plastic washer between them. Don’t they come with a rubber washer originally?
Tony

[yelcab1]

I never use SS fasteners on a car. Once you drop a SS nut into a crevice and you cannot find it with your magnet, you will swear off SS fasteners forever. If I work on a car and I find a SS nut or bolt, I throw them out and replace them with a steel one.

[Canada Kev]

I know a guy that was sick of replacing steel fasteners on the floats of his plane. With aircraft, the regulatory bodies are kinda finicky about having things like rusted bolts on your landing gear. Turns out they don't like it so much.

So to fix it once and for all, he replaced them all with stainless. It worked fantastic! No more rusting bolts! Well, until it was discovered that his floats, which are made of aluminum, were corroding. A lot. It turned out to be a rather expensive repair.

Replacing the regular steel bolts periodically seems pretty inconsequential now.

Mild steel and aluminum are pretty close together on the galvanic scale, so there is less potential for a strong reaction. When the stainless, from quite a way down the scale, was introduced instead of the steel, all those aluminum electrons were just leaping off those floats.

Theres a reason they use zinc anodes on boat drives. It's just about at the furthest end of the galvanic scale and makes a great sacrificial metal so your prop is protected from corrosion.

[slow&rusty]

All great points especially using steel fasteners in the engine bay and fishing them after they've been dropped out with your favorite goose neck or telescoping magnet, we've all been there.

Having said ARP is the most trusted brand for engine fasteners (not just head studs) and we all know their material of choice.

[911pcars]

Originally Posted by slow&rusty

All great points especially using steel fasteners in the engine bay and fishing them after they've been dropped out with your favorite goose neck or telescoping magnet, we've all been there.

Having said ARP is the most trusted brand for engine fasteners (not just head studs) and we all know their material of choice.

Not all engine fasteners have use ARP spec fasteners. Only a few key high stress areas required them (e.g. crank and rods). Up to you to install ARP fasteners to hold valve covers, tin metal, air shrouds, etc. in place.

Sherwood