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[johnnydog]

Wondered if any of you knowledgables have had any experiences of this issue...
I have a set of ceramic front brake calipers on an Audi (which I believe are made by Brembo). The inner bleed nipple on both calipers have seized primarily I presume as the bleed nipple is steel and the caliper body is alloy causing corrosion between the different metals
The brake system has been bled religiously every two years.
I have a chap who has had success of removing seized / snapped bleed nipples so I'm not overly concerned about getting out - but should I replace them with stainless steel or titanium alternatives?
I have researched this on t'interweb, and I'm leaning towards a high grade of stainless with maybe a smear of ceramic brake grease or red rubber grease on the thread,  but there is some suggestion that titanium and alloy are possibly better suited to the different metals, although there will aways be some reaction over time.
I am a little miffed that dispite them being slackened to bleed every two years they have seized, but if I can reduce the likelihood of this problem in the future, which alternative metal bleed nipple would be best?
Thanks

[Nick W]

I'd tend towards stainless, because you've only got to look at titanium bolts and they snap.


You are fitting rubber caps to keep the nipples clear? Most of the seized ones I've seen have been where the sealing taper at the bottom was corroded

[johnnydog]

Thanks Nick - they have always had the rubber caps on the nipples. Stainless was my thoughts too of the the two metals from what I've read. Checked the cost of them and they aren't too bad price wise either.

[johnnydog]

After doing more digging, I think I will stick with original Brembo /Audi steel replacement bleed nipples.
Reasoning behind it - galvanic corrosion when two types of metals are in contact with each other (as we all know), and an electrolyte (humidity / rainwater/ sea or salt water etc). Alloy calipers are made from an aluminim alloy I understand, and this corrosion requires an anode and cathode to start the process, if the  two metals are similar this process is reduced.
Unfortunately stainless steel and aluminium alloy are more prone to electron transfer, and titanium even more so; mild steel or zinc plated steel less so. In other words the more similar the metal are between anode and cathode, the less galvanic corrosion occurs.
You would have thought the engineers at Brembo would fit the most appropriate bleed nipples for the metal in their calipers, so with that in mind, I am going to stick with their standard bleed nipples. I'm not saying galvanic corrosion won't occur again, but with a barrier on the threads such as ceramic grease or red rubber grease (being unaffected by brake fluid) should help to reduce the effect.
Took some research but stainless in alloy, and titanium in alloy are not recommended at all unless sleeved with a more compatible metal.
Now have to get the snapped and seized bleed nipples out......