Thread: I need advice on a crumbling edge.

Originally Posted by Casey302

Here’s one theory -

“The combined effects of stress and corrosion can result in a special type of failure known as Stress Corrosion Cracking (SCC). This arises under a particular set of circumstances for a given alloy: specific alloy condition plus specific corrosive media and sufficient local tensile stress. Chloride induced cracking of stainless steels, caustic cracking of plain carbon steels and ammonia damage to copper alloys are typical examples of this problem.

SCC is believed to be nucleated at pitting damage sites and develops under the action of local tensile stresses as a highly branched network of fine cracks. At each crack tip the combined action of the tensile stress and specific ions in the corrosive media cause continual crack propagation with little evidence of local deformation.

Stress corrosion cracking presents an especially difficult problem, since not only is it highly localized but it can occur in environments that are merely mildly corrosive to the material. The damaging concentration of the harmful ions in that environment may be quite small and difficult to detect and, even in the absence of applied stress, residual stresses in a structure can often be of a sufficiently high level to cause SCC and failure in service.
In a given situation the time of exposure needed to cause SCC failure depends on the stress intensity at any pre-existing or developed crack tip. The concentration of stress at the tip of a sharp crack or flaw can be quantified in terms of the Stress Intensity Factor, K1. It determines the growth rate of SCC cracks for a specific alloy environment combination. Catastrophic failure of a component will occur when this factor reaches a critical value, the Fracture toughness of the material, K1C. This enables the determination of allowable defect size in design to avoid failure under given loading conditions.”
Your fine old Wade & Butcher has likely been exposed to over 100 years of corrosive influences and in all probability the stress induced in the polishing & honing process was sufficient to begin the failure.

There is obviously no way of telling how far the micro-cracking permeates the metal or how much will have to be removed to find that perfect edge, but I wish you good luck!

pretty cool. caustic cracking. As I was reading along I thought corrosion could have been hiding in micro cracks. SCC is different from regular ole corrosion?
Are these effects more a concern for bridge engineers? If a pitted razor rests for too long with a bar of lye soap; will that cause it? We need to capture these ions and use them to sharpen with

At Bart's magnification wouldn't we be able to detect discoloration, possibly?

I guess not if the ions are banging away on the inside? something like that?

Originally Posted by kevint

At Bart's magnification wouldn't we be able to detect discoloration, possibly?

I've made another picture.
You guys are gonna have to take my word for it, but the edge was flawless before the test shave. Every damage you see was caused by a few swipes WTG.
The visual shows no discoloration. My picture does, but it's caused by my small led light source and the fact that I shoot those pictures through the eye piece of the scope. Magnification of this picture is 30X.
I initially planned to hone a bit further tonight, but I haven't found the courage yet.

Thanks,
Bart.

on the other side- are those chips or curls?

There's that 8tape bevel line.
It's obvious now that you say 30x. Of course. I think you'd need a bit higher be sure there is no visible corrosion.

I can see those pits though

Firstly Bart can I say wow. The improvement on what was there when it left me is huge and immediately obvious!

Secondly a thought occured to me. Is there any chance that what looks like bog standard pitting on the actual blade is in fact something much deeper? Something that might go all the way to the core? That might explain why 1 shave WTG has brought out what appear to be a series of small indentations or semi-circles in the edge?

Just a thought...

Originally Posted by kevint

on the other side- are those chips or curls?

The chunks are completely missing, probably embedded in my face somewhere.

Originally Posted by Bart

I've made another picture.
You guys are gonna have to take my word for it, but the edge was flawless before the test shave. Every damage you see was caused by a few swipes WTG.
The visual shows no discoloration. My pictures does, but it's caused by my small led light source and the fact that I shoot those picture through the eye piece of the scope. Magnification of this picture is 30X.
I initially planned to hone a bit further tonight, but I haven't found the courage yet.

Thanks,
Bart.

Sorry Bart and Sydney. But after seeing this picture... I am 90% sure the edge problem is corrosion. Those pits are pretty deep and very close to the edge. I'm going to have to weigh in on the side of caution and save what you can.

Originally Posted by Leighton

Sorry Bart and Sydney. But after seeing this picture... I am 90% sure the edge problem is corrosion. Those pits are pretty deep and very close to the edge. I'm going to have to weigh in on the side of caution and save what you can.

Corrosion doesn't automatically equate to an unsound edge or most restored razors would be crumbling.
Bart's pic shows no pits in the bevel. In his words it was a "flawless" edge that crumbled after shaving.

Originally Posted by onimaru55

Corrosion doesn't automatically equate to an unsound edge or most restored razors would be crumbling.
Bart's pic shows no pits in the bevel. In his words it was a "flawless" edge that crumbled after shaving.

No, but taking all the evidence into consideration, the probability that the blade has been infected with that SSC? problem seems very likely. Or at least more likely than not. The pits are pretty close to the edge too, thus razor is questionable at best. I would personally leave it alone. But thats only one vote and one opinion. And in the end, my vote doesn't count anyway.

I thought that this might be of interest - it shows how the external appearance of the pits may markedly differ from the extent of pitting under the surface.

The darker material in the base of the pit can hide what is going on beneath it. It produces a kind of micro-environment in which an electrochemical action can occur - the pH value in the pit can fall, become acidic, a cathodic/anodic reaction can occur. If this leads to intergranular corrosion the metal is weakened.

Regards,
Neil

Very interesting Neil. The pit turns out to be like an iceberg in some cases. Worrisome on at least one of the old Sheffields that I haven't gotten around to yet. Those pits in Bart's project could very well be extending beyond what is apparent on the surface. I would have never imagined that could happen.