Rusty nuts!

[belfry]

I attach a photo of a rusty nut on my ceramics. 2012 28k
About 50% have a tiny bit of surface rust.
I'd like to deal with this now, before they start to corrode.
They are 8mm nuts, I did try removing one but it was very firmly stuck and I did not want to damage the nut. Do I replace or treat them with some product?
Many thanks guys.

[stevieturbo]

Between water, salt, wheel cleaners etc etc, they will just corrode again. So probably no point worrying too much.

If you really think they must be changed for new, contact a brake specialist for suitable replacements.


They will be a locking nut/interference fit, so will be a little tighter to undo, but still a small fastener in general so just swing on it.

[anonymous-user]

Can you swap them for stainless steel?

[500TORQUES]

Brake bell bolts and nuts are usually a one fit only item.

If you undo them, fit genuine new replacements.

[PhillipM]

They're k-nuts, they're steel, they're going to get a bit of surface corrosion, and as someone said, if you remove them ideally they should be replaced - they have a deformed thread that provides the locking effect.

I'm not sure you're going to find anything paint wise that will stay on them even if you clean them up given the temperature. VHT paints will cope with the temp but they're generally so fragile they won't stop corrosion from the road salts.

[belfry]

I have covered each one with a little ACF-50 on a small paintbrush.
Motorcyclists swear by this stuff for rust prevention as do the Air Force who use it on aircraft based on aircraft carriers.

[E-bmw]

pocketspring said:

Can you swap them for stainless steel?

Don't.

For one stainless nuts/bolts don't cope well with temperature cycles & will seize in place.

And for another reason stainless may well not be up to the HT spec of what is fitted as it is generally of a lower stress value.

[ChocolateFrog]

belfry said:

I have covered each one with a little ACF-50 on a small paintbrush.
Motorcyclists swear by this stuff for rust prevention as do the Air Force who use it on aircraft based on aircraft carriers.

Needs doing from new really.

Literally only takes one salty, wet drive to turn untreated or lightly treated steel orange and aluminium white.

Bilt Hamber Atom-Mac, which was recommended to me on here is good as a maintenance spray, quick spray after every wash seems to keep the worst of it off.

[anonymous-user]

E-bmw said:

pocketspring said:

Can you swap them for stainless steel?

Don't.

For one stainless nuts/bolts don't cope well with temperature cycles & will seize in place.

Genuine question. Why are decent exhausts made from stainless then? Thinking about heat cycles and even thermal shock when going through a cold puddle.

[E-bmw]

pocketspring said:

E-bmw said:

pocketspring said:

Can you swap them for stainless steel?

Don't.

For one stainless nuts/bolts don't cope well with temperature cycles & will seize in place.

Genuine question. Why are decent exhausts made from stainless then? Thinking about heat cycles and even thermal shock when going through a cold puddle.

Exhausts are fine as it is (basically) just a pipe, but you will not see them bolted together with stainless bolts/nuts as the nuts will not come off without stripping the thread after a few heat cycles.

[anonymous-user]

E-bmw said:

pocketspring said:

E-bmw said:

pocketspring said:

Can you swap them for stainless steel?

Don't.

For one stainless nuts/bolts don't cope well with temperature cycles & will seize in place.

Genuine question. Why are decent exhausts made from stainless then? Thinking about heat cycles and even thermal shock when going through a cold puddle.

Exhausts are fine as it is (basically) just a pipe, but you will not see them bolted together with stainless bolts/nuts as the nuts will not come off without stripping the thread after a few heat cycles.

That's interesting, my Miltek came with stainless jubilee clips.

[belfry]

ChocolateFrog said:

Literally only takes one salty, wet drive to turn untreated or lightly treated steel orange and aluminium white.
.

This is why I like ACF-50, as it penetrates and forms a film over the area. Almost like a wax. I treat the undersides of my vehicles every other year and it's really quite tenacious from what I've observed.

[E-bmw]

pocketspring said:

E-bmw said:

pocketspring said:

E-bmw said:

pocketspring said:

Can you swap them for stainless steel?

Don't.

For one stainless nuts/bolts don't cope well with temperature cycles & will seize in place.

Genuine question. Why are decent exhausts made from stainless then? Thinking about heat cycles and even thermal shock when going through a cold puddle.

Exhausts are fine as it is (basically) just a pipe, but you will not see them bolted together with stainless bolts/nuts as the nuts will not come off without stripping the thread after a few heat cycles.

That's interesting, my Miltek came with stainless jubilee clips.

Stainless jubilee clips, yes, stainless Mikalor type clamps even, (although they often have BZP screws in them) but did the flange bolts/nuts come in stainless?

Edited by E-bmw on Monday 3rd April 17:40

[anonymous-user]

E-bmw said:

pocketspring said:

E-bmw said:

pocketspring said:

E-bmw said:

pocketspring said:

Can you swap them for stainless steel?

Don't.

For one stainless nuts/bolts don't cope well with temperature cycles & will seize in place.

Genuine question. Why are decent exhausts made from stainless then? Thinking about heat cycles and even thermal shock when going through a cold puddle.

Exhausts are fine as it is (basically) just a pipe, but you will not see them bolted together with stainless bolts/nuts as the nuts will not come off without stripping the thread after a few heat cycles.

That's interesting, my Miltek came with stainless jubilee clips.

Stainless jubilee clips, yes, stainless Mikalor type clamps even, (although they often have BZP screws in them) but did the flange bolts/nuts come in stainless?

Edited by E-bmw on Monday 3rd April 17:40

I don't know tbh, the garage bought them as they weren't supplied. (Which quite surprised me. )

[dhutch]

E-bmw said:

pocketspring said:

Can you swap them for stainless steel?

Don't.

For one stainless nuts/bolts don't cope well with temperature cycles & will seize in place.

And for another reason stainless may well not be up to the HT spec of what is fitted as it is generally of a lower stress value.

This.

[dhutch]

You can get A4-80 Stainless bolts are around the same tensile strength as an 8.8 grade mild steel bolt. Which should be ok for most things. But those nuts, caliper bolts, that sort of thing are often 10.9 if not 12.9 so fitting a SS bolt could only 60% of the tensile strength or less.

As said, galling of stainless steel is definitely an think as well, not so bad if one side is steel. But SS in SS, while often fine, can very quickly become an absolute nightmare.

[E-bmw]

dhutch said:

not so bad if one side is steel. But SS in SS, while often fine, can very quickly become an absolute nightmare.

Quite true, one other option is SS bolts/flashed copper nuts, but then you might as well just use BZP/Copper.

[poppopbangbang]

If you want to replace them for something which will corrode slower/less then use silver coated high temp K-Nuts in place of standard K-Nuts: https://race.parts/Catalogue/Tapes/K-Nuts/Metric-H... generally these are designed for turbos, exhaust manifolds etc. but are directly compatible with standard K-Nuts albeit with a different surface coating that is more corrosion resistant.

Make sure you know the torque spec for the bell/disc/bobbin combination and torque them up opposites.

DO NOT use a stainless or a washer/nut combination unless you know how to do the calcs to ensure they are 100% suitable. Whilst your setup has anti-rattle bobbin springs there are always some weird harmonics going on in floating discs that will make short work of undoing anything which isn't sufficiently self locking, the absolute gold standard of will not come undone is a K-Nut hence their use here.

Note: You should also replace the bolts at the same as good practice, however bolts twice, nuts once assuming all the threads of the bolts are in good order and undamaged will be okay if they haven't been used previously.

P.S. ACF-50 has a flash point of circa 80 degrees C, it's great at preventing corrosion in ambient operating temperature assemblies/vehicles but doesn't do well with heat as it cooks off very easily.

[belfry]

Thank you for a very informative post. I had no idea about most of that, especially the point about ACF-50 and 80 degrees.

[belfry]

How about applying a ceramic coating to the nuts? Could that work?