Although the effect might not be immediately obvious, I would expect peroxide to cause rusting of the knife. It is a strong oxidizing agent (unsurprisingly) and I doubt if it is doing your blade any good at all (even if it is supposedly “stainless”). I would look for another way of cleaning it.
Right.
I use a glass of ordinary consumer-grade hydrogen peroxide to sanitize my snoring mouthpiece, and got to wondering how long it would take for the stuff to become ineffective.
So I set out a fresh glass every other day for about ten days, until I had six glasses ranging from 1 to 10 days old. I then tested the reactions I got when I poured the samples on some yeast, a technique I read about on the Web somewhere, since I didn’t have any lab equipment to do more sophisticated tests.
I had expected to get more reaction from the fresher samples and less from the older ones, since I assumed that the stuff would decompose over time.
To my surprise, the results were the opposite: the older samples gave stronger reactions with the yeast. I realized that the water used to dilute it was evaporating, leaving a higher concentration of H[sub]2[/sub]O[sub]2[/sub] behind.
Of course, I can’t say what would happen over a much longer period of time.
Yes, a girlfriend took and ancient bottle of H2O2 out of her medicine cabinet. It was marked 3%. But it reacted, killing the surface cells on your hand. Much like 35% food grade H2O2 would do.
The boiling point of water is 212 °F, but the boiling point of H2O2 is 302.4 °F. So the water would disappear first, leaving behind higher amounts of H2O2.
and applied it on an ancient post 
Cleaned it up, but I don’t think damaged it at all.
Just what is the half life of H2O2 ?
I have doubts about your conclusion. The problem is that H2O2 breaks down over time releasing oxygen and leaving water behind. Concentrating H2O2 even with controlled distillery is difficult, reaching 35% concentrations just from an old bottle sitting around doesn’t fly. At best the solution left over has a higher than normal concentration of dissolved oxygen, nothing like the concentration of 35% H2O2 though. Even weaker than 3% solutions of peroxide will react with dead skin cells pretty vigorously, 35% would bleach skin very obviously.
I don’t think the O2 concentrations above the water would produce H2O2 in neutral or hydroxide ,pH > 7, water.
In neutral, or ph> 7 clean water (no catalyst) Peroxide does SLOWLY break down.
But it seems that in the water with pH < 7, peroxide is stable. The lack of dependency on temperature seems to suggest that its simply stable , and neither is peroxide breaking apart, nor being made.
With the break down rate being so slow, le chateliers doesn’t seem to be relevant, its not a reaction that le chateliers is in control of… there isn’t the forward and backward reaction happening.
… Dissolving O2 into water is not a way to make perodixe.
Two chemists take a break for lunch. One says “I’ll have a glass of H20” The other says, “I’ll have a glass of H20, too”. Only one chemist returns to work that afternoon.