Black oxide SS fastener durability?

[shakenfake]

Need black fasteners for a project, only want stainless steel. I can purchase black oxide stainless steel fasteners on MMC or Fastenal but everywhere I look it says they corrode and turn orange. How is stainless turning orange? My brain is not computing this. In my head the black oxide is just a finish and shouldn't degrade when not put under stress. Does anybody have any thoughts on this?

These fasteners will be going on a car that sits in an AC garage 99% of the time, lives in the south, and the only water it sees is when I am washing it.

Thanks

 

[PugetDude]

I suspect the orange is rust bleeding from the mild steel they are screwed into.

 

[shakenfake]

Perhaps, these will be screwed into a powder coated piece so unless it is the threads rusting outwards... I will be coating the threads with antiseize.

I did think about powder coating the heads but I wanted to try the black oxide stainless first. Once installed I probably will never see them again. Basically just minute details.

 

[MoonRise]

Black oxide (the real thing anyway, not a paint or other surface coating) is black IRON oxide (commonly magnetite Fe3O4), aka a form of rust. It offers minimal corrosion protection, most of which comes from oiling or waxing the black oxide. Regularly.

Given the right (wrong) conditions, it will change from black iron oxide to red iron oxide (typically Fe2O3).

Want black with no rust? Stainless fasteners and then paint (or powder coat) them. Be aware that painting stainless steel can actually cause it to rust though, as the chromium in the stainless steel needs to be exposed to oxygen to form a chromium oxide film on the stainless steel which is what protects the iron in the alloy from turning into iron oxide (aka rust).

Maybe look into black zinc coating. Black color, but actual zinc coating protection. Not as much protection as galvanized though.

If you are never really going to see the fasteners though, just use the stainless steel with no coating and be done with it.

What is the specific application for these fasteners? Other than somewhere on a car, which will be mostly in a garage in Texas. With heat and humidity. And water from when it gets washed. Or when the humidity condenses.

 

[shakenfake]

Thank you @MoonRise for the explanation. I will see if I can find anything with black zinc coating. Or last resort I will just powder coat them. I am worried that paint will chip pretty quick if I wrench on it.


They hold the clips for my parking brake Circled in red and there are two on the back of the plate.

 

[shakenfake]

I see Caswell makes a stainless steel blackener kit.

I am open to move away from stainless steel, I mainly just wanted to avoid rust and corroded fasteners. I am not very learned on that sort of thing quite yet.

 

[Blk88GT]

I too prefer the black fasteners and use them. The black will rust.

 

[Colin Len]

I've had terrible luck with black oxide. I assume the stuff I've used wasn't SS though, but not sure. Either way, for me black oxide is something I now stay away from. I wouldn't hesitate to use it inside our house but anywhere outside or on a vehicle...no way.

Maybe look into black zinc coating. Black color, but actual zinc coating protection. Not as much protection as galvanized though.

^This is the answer. Although finding black zinc hardware may be tough or impossible and having it done by a shop may be very expensive if you're only doing a couple bolts (the shop I use has a $150 minimum).

Personally, I would stay away from powder coat. It will add thickness and will be prone to chipping off when tightened/loosened. You'll have better luck with a thinner coating with better adhesion than powder - like Zinc, PVD or possibly a thin ceramic like Cerakote. You may be able to find a local shop that does Cerakote and is willing to take small orders. Lots of these guys do gun parts so I imagine they take in small orders and then do regular weekly/bi-weekly coatings of their common colors. I haven't found anyone that does that with zinc, they all want large orders.

 

[MoonRise]

Not a Concours d'Elegance level restoration?

Just use the stainless steel fasteners (for the rust resistance) and move on. They will get coated in grime and brake dust and dirt soon enough. Of course, if the stainless steel gets coated in brake dust it will probably rust or corrode (at least on the surface) anyway.

Be aware that most stainless steel fasteners are not as strong as alloy steel fasteners. Short of $$$$ aerospace-type stuff. They can be plenty strong enough for many uses, but if something originally used Grade 5 or Grade 8 (or metric Class 10.9 or 12.9) fasteners you NEED to use the original strength level of fastener in that application. Grade 5 bolt (three hash marks on the hex head) has a tensile strength of 120 ksi, Grade 8 (six hash marks on the hex head) is 150 ksi, and common 18/8 aka 304 is 70 ksi. Metric Class 10.9 has a tensile strength of 150 ksi, Class 12.9 has a strength of 170 ksi. Grade 2 (no hash marks on the hex head) bolts have a tensile strength of 60 ksi.

What's the car? Come on, we like car pics.

 

[shakenfake]

@MoonRise Lol not that level of restoration. Not really a restoration at all. I just like to be fancy.

I think I put 200 miles on it in the past two years lol, most of that being my own fault as to not putting more.

I will have to double check the fasteners then. I know for those little screws I can surely use the stainless. I think you are correct on the rest though and I probably will end up using galvanized.

It is a 1996 Impala SS. It needs some work but it is still a beautiful car that I love dearly.





I removed my rear axle and did 3.73 gears, truetrac, new axle shafts, TA girdle in raw aluminum, new bearings and seals, powdercoated in satin black. I need to replace all of my control arm hardware (mostly the nylon locknuts from 20 years ago) but also some of the little screws and stuff that I feel could be replaced to look better. It will look great for about 10 minutes and then my leaky LT1 will drench it in oil

 

[RPH]

Nice car and @MoonRise excellent wright up!

 

[shakenfake]

Thank you @RPH

I will search for another solution. Thank you everyone for the help! For now I will most likely continue with the recommended equipment.

 

[LXCam]

Like has been said. I did one show motor including alllll the fasteners on a twin screw blower build and the exposed stuff in the engine bay ONCE. they turned to **** within a year. I only use stainless now and occasionally anodized bezels in red or black to make it pop.

 

[CraigStu]

I am not a fan of SS bolts and nuts. Back in our boating days I used them a lot. Never was sure where I had originally bought a bolt, ACE or West Marine since I shopped at both. But some of them did rust. More recently I built 2ft walls for my little 4'x4' trailer to haul trash cans to the dump. I used 3/8 PVC sheet and a bunch of SS bolts, SS washers, and SS Nylocks. Had a small tree fall and knock off a 6x6" chunk of one of the sides so I needed to take it partially apart to replace part of one side. The bolt heads were round w/ phillps screw and my bit was skipping when I hit it w/ the drill to remove. Ok, grabbed a more perfect fitting bit and used a 1/4 drive ratchet. Well he11, 3/4 of the nuts had galded onto the bolts. It sits outside but is always covered w/ a well tied down tarp. From now on, I will be skipping SS altogether.

 

[shakenfake]

@CraigStu It sounds like you didn’t put any lube on the threads. Unless it was like a major time period between the assembly and disassembly

 

[LXCam]

Stainless hardware requires antiseize every time.

 

[MoonRise]

Stainless on stainless means you better use antiseize or you risk galling the threads of the bolt/screw to the nut.

Especially if you have the same alloy stainless on both threads. If you have different alloys (ex 304 on 316) on the bolt/screw and the nut you lessen the risk of galling the threads. If you have different 'family' of stainless (austenitic against martensitic, austenitic against ferritic, etc) you reduce the risk of galling a little more.

BTDT. Galled a stainless bolt into a stainless nut so badly that they were effectively welded solidly to one another (that's what galling is btw, it is a diffusion/pressure welding process of the two pieces) that the only way to get it apart involved a LONG cheater bar and a hella lot of grunt to literally break the parts in two. We then took a lunch break and on the way back stopped off at the local industrial supplier place and got some antiseize. Used it liberally for the installation of the rest of the fasteners and had no more problems.

 

[kabinenroller]

I used almost all steel fasteners plated with “ yellow” Zinc on my last build, I used some stainless but very little. The gold color of the zinc looks good, especially when the brackets etc. are plated the same color. I have also Parkerized all the hardware on some of my restorations, it is a charcoal black color that is very similar to what was used when the vehicle was assembled at the factory. Both coatings have held up well but these vehicles are not everyday drivers.

 

[BillK]

shake,

What size are the fasteners ?

Check out one of my customer's pages on you tube:

 

[CraigStu]

@CraigStu It sounds like you didn’t put any lube on the threads. Unless it was like a major time period between the assembly and disassembly

You are correct. I hate anti-seize so almost never use it. In the case of my little trailer, it wouldn't matter but, in general SS isn't as strong as G5 bolts so another strike against it.