Hi Folks!
The corrosion of which we speak is simply oxidation - oxygen forming a bond with the iron in steel to form iron oxide - rust.
For oxidation to occur only oxygen and iron are required, and it doesnâ??t matter where the oxygen comes from - water or blood.
> There is a much higher concentration of salt in blood is
> there not? Salt is highly corrosive
Respectfully, and with no offense intended, salt is not corrosive. Corrosion occurs more quickly in the presence of salt because salt attracts and holds water. It isnâ??t the salt that is producing rust - itâ??s the water attracted by the salt.
> that blood carries a -much- higher concentration of oxygen
> than H2O, as haemoglobin is an oxygen fixitive;
Blood contains less oxygen than does water per unit - water is one third oxygen. The oxygen in blood is less tightly bound that is the oxygen in water. Water has more oxygen, blood gives up its oxygen more easily, making it a wash as to which will produce more iron oxide faster.
> Assuming that "blood pitting" is a real phenomenon, does it
> operate differently on a rust-blued surface than it does on
> a salt-blued surface? Is the oxide-blued surface somehow catalytic?
No, sir. Both rust and salt blue produce oxide surfaces. In essence, the iron in the surface of the steel becomes bound in a stable compound with no room for another oxygen atom regardless of which process is used. The rust blue process tends to produce a deeper layer of iron oxide than does the salt blue process, and rust blue finishes are somewhat more durable as a result.
Be all that as it may, both bluing methodologies create the same stable surface oxide compound. The normal concentration of oxygen in the atmosphere cannot bind to this blued surface and the surface will not further oxidize. However this stable surface oxide can be over-powered by a concentration of oxygen (as is present in blood or water) and further oxidation will then occur.
If we were to put a drop of water and a drop of blood side by side on a Luger frame and leave it for a week, and then clean and present the frame to a third party that third party would be unable to tell the difference between the two spots of oxidation, or to tell which spot of oxidation was caused by which oxidizer.
Gentlemen, over the years Iâ??ve bled on a whale of a lot of firearms and can tell you from my own experience that blood is not especially corrosive. A sweaty finger print will produce more rust faster than will a bloody finger print.
I respectfully and with no offense intended to anyone maintain by my earlier opinion that the stories of â??blood pittingâ?? are fanciful attempts to make poor maintenance marketable. The people who try and sell â??blood pittingâ?? are doing the same thing as those who try to sell â??General DWMâ??sâ? Luger :-)
Warm regards,
Kyrie
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