staticmind

Hi,

This seems like a great forum - will introduce myself in the introductions thread later.

I stumbled upon a few other threads on Ti bolts in this forum (sorry, can't post links), but have not found any threads describing the more technical details. My own experience with A2-70 (304) stainless steel bolts for a stem made of 7075 alloy (I believe) has been that the stem began to corrode after about half a year. Some years later I cleaned the corrosion off as well as I could and replaced the bolts with titanium alloy bolts ("grade 5" bolts). This is now many years ago, and the aluminum has not corroded since, or very little if any. I have now bought some more grade 5 bolts for a different bike project, but didn't think of this before now:
Shouldn't the titanium bolts make the aluminum alloy corrode even faster than with the stainless steel bolts? I mean, the titanium itself is supposed to be more cathodic than 304 stainless steel - or is the fact that aluminum is present in the grade 5 alloy (6Al-4V) making it much less cathodic and thus much less corrosive than 304?

ClydeClydeson

Maybe better in terms of corrosion, but not suitable for strength in an application intended for steel bolts.

Litespud

Not wild about small Ti fasteners - I heard too many (granted, anecdotal) stories of such fasteners failing. Whenever I buy a lightweight component with Ti screws (stems, usually, where screw failure is not an option), I replace the screws with quality black oxide-coated steel equivalents. Yes, they surface corrode over years, but that's all it is. I took a look at MacMaster-Carr, my "go-to" for fasteners, and they list Grade 5 (6/4) Ti as having a tensile strength of 130,000 psi, compared with 170,000 psi for good alloy steel, so there's no strength advantage. Anyway, you should be greasing your fasteners, and regreasing them every couple of years, which should negate any tendency to corrode

dsbrantjr

My go-to treatment for dissimilar-metal joints is Tef-Gel: https://www.tefgel.com/contain.php?param=tefgel_infor
I am not a fan of Ti fasteners, they have issues such a fretting corrosion which requires the joining system to be specifically designed for them, and except for weight (which doesn't generally concern me) and "sexiness" I see little advantage over steel.

HillRider

I've done the opposite and used aluminum alloy water bottle cage bolts in Ti frames for decades with no corrosion problems. My secret? Grease the bolts.

sweeks

I've been using titanium fasteners on my "winter" bike for at least 10 years. Brake pivot bolts (V-brakes), brake shoe hardware, chainring mounting bolts, crank mounting bolts. No strength issues or corrosion. Actually, *no* corrosion in spite of being ridden in a salty environment. I also have a titanium seatpost clamp bolt on my mountain bike. If I have a titanium bolt in a titanium frame, I use a copper-based anti-seize paste (also between a Ti seatpost and a Ti frame).
There is no real weight advantage, as dsbrantjr points out, unless you're counting grams. I don't know about "sexiness", but Ti hardware does look nice.

Stainless (L) and Ti (R) chainring hardware



Original stainless hardware (L) vs Ti (R)



Split image: SS hardware in the top half, Ti in the bottom.

bitpuddle

A stem corroding after six months seems really unusual. Is it used daily on an indoor trainer? Left outside exposed to salt water?