69 caliper fasteners

[Chuck S.]

Re: What We Need...

I thought hydrogen embrittlement wasn't reversible; annealing had to happen soon after plating or molecular hydrogen formed in the interstices, cracks developed, and failure happened soon after torqueing regardless of how much later they were used. Perhaps heating causes the bonds of the hydrogen molecules to break down and the atomic hydrogen escapes through the grain structure, but I would think cracks that have already developed can't be fixed.

If HE fixes itself with time, my fasteners have already "healed" themselves. If not, I suppose I could "throw a few bolts on the barbie" when I start putting this thing back together.

[Michael H.]

Re: What We Need...

That's the way I always thought it was too Chuck. Once the small cracks develop, I don't understand how they would "heal" in time. I have to think that it takes a certain period of time for the cracks to develop which is why the heating process would be required soon after the acid bath. This may be a good homework assignment for me tonight.

[Joe L.]

Re: IMO black oxide

Chuck------

Some grade 8 fastners were black phosphate, but I don't think that these, particular, ones were. I definitely agree that after corrosion sets in, it's difficult to tell the two finishes apart.

[Mark A.]

Re: What We Need...

Ok, I've read all the replys and highly technical responses which for the most part are way over my head. My simple question would be, am I causing structural damage, that is creating an unsafe condition, by bead blasting and then soaking for 60 seconds in Eastwoods blackening solution my caliper bolts? The solution has phosphoric acid along with copper and a few other elements. Thanks, Mark

[Joe L.]

Re: What We Need...

Mark------

If you do it as you described, I don't think that you'll affect the structural integrity or strength of the bolts.

In general, though, I do not recommend the re-finishing of any high strength bolts used in applications in which high strength is critical if that re-finishing involves any electroplating processes OR any process using a strong acid (phosphoric is, incidentally, a weak acid).

Also, I do not recommend the re-use of any high strenth bolts used for high strength applications if the history of those bolts is unknown OR if the bolts suffer from ANY corrosion which has caused pitting. "First run" bolts are ok for re-use. By "first run", I mean bolts that were originally installed at the factory and removed the first time by you. Bolts which have once-upon-a-time been removed by others and re-installed by others do not qualify as "first run".

By the way, Paragon offers reproduction caliper-to-bracket bolts which are, in my opinion, indiscernable from the originals and correctly black-oxide finished. They are not very expensive, either. All things considered, I don't think that it's worth it to "dink around" with trying to refinish these.