In a recent thread on another forum, the discussion came up about using hydrogen peroxide to remove metal stains. At first I didn't think this would work, but then realized that hydrogen peroxide is both an oxidizer AND a reducing agent. So using it in place of ascorbic acid is viable. It's also a LOT less expensive. As I calculated in a post in that thread, hydrogen peroxide at $18 for one gallon of 27.5% (in BioGuard® SoftSwim® C) is far less expensive than ascorbic acid at $8-9 per pound. One pound of ascorbic acid reduces 4.8 ppm FC in 10,000 gallons while one gallon of 27.5% hydrogen peroxide (1.12 g/ml density so 1.166 kg hydrogen peroxide) reduces 64.2 ppm FC in 10,000 gallons. So the hydrogen peroxide is 28 cents per ppm FC in 10,000 gallons while ascorbic acid is $1.67.
The reducing power vs. chlorine gives the capacity, but not necessarily the effectiveness against metal stains. Nevertheless, it worked very well for one user and is probably something that people could try here on a selective experimental basis to see if it works against new stains and old stains. If it does, then it's far less expensive than ascorbic acid and it produces no disinfection by-products to get rid of it since chlorine reacts with hydrogen peroxide to produce oxygen gas.
HOCl + H2O2 ---> H2O + O2(g) + H+ + Cl-
Hypochlorous Acid + Hydrogen Peroxide ---> Water + Chloride Ion + Oxygen Gas + Hydrogen Ion
One difference in the ascorbic acid treatment vs. hydrogen peroxide is that ascorbic acid is acidic while hydrogen peroxide is not so if one uses hydrogen peroxide then one needs to use regular acid to lower the pH for the treatment. With ascorbic acid one did this as well but didn't need to use as much acid because the ascrobic acid itself was acidic. Also, as noted above, if you use a lot of hydrogen peroxide, then when you add chlorine to get rid of it the pH will drop and will need to be adjusted upward once one starts getting a Free Chlorine (FC) reading.
The reducing power vs. chlorine gives the capacity, but not necessarily the effectiveness against metal stains. Nevertheless, it worked very well for one user and is probably something that people could try here on a selective experimental basis to see if it works against new stains and old stains. If it does, then it's far less expensive than ascorbic acid and it produces no disinfection by-products to get rid of it since chlorine reacts with hydrogen peroxide to produce oxygen gas.
HOCl + H2O2 ---> H2O + O2(g) + H+ + Cl-
Hypochlorous Acid + Hydrogen Peroxide ---> Water + Chloride Ion + Oxygen Gas + Hydrogen Ion
One difference in the ascorbic acid treatment vs. hydrogen peroxide is that ascorbic acid is acidic while hydrogen peroxide is not so if one uses hydrogen peroxide then one needs to use regular acid to lower the pH for the treatment. With ascorbic acid one did this as well but didn't need to use as much acid because the ascrobic acid itself was acidic. Also, as noted above, if you use a lot of hydrogen peroxide, then when you add chlorine to get rid of it the pH will drop and will need to be adjusted upward once one starts getting a Free Chlorine (FC) reading.