sodium metabisulfite reaction

[QuiQuog]

Any idea what this reaction is? I put 4tbsp of sodium metabisulfite in a gallon of water and put it in a 10 gallon brute, along with some things I wanted to disinfect. All plastic or glass. I didn’t have a lid for it, so I put this large stainless steel bowl over it. Came back a few days later to this rusty goo all over the bottom of it. It doesn’t rinse off, but I managed to scrub it off with a brush, but it’s left behind black bumps that I haven’t got off yet.

 

[QuiQuog]

Well, it’s actually pits. It ate through and ruined my big beautiful stainless bowl.

 

[Rocky]

Well, it’s actually pits. It ate through and ruined my big beautiful stainless bowl.

I am not a metallurgist, but my guess would be that you etched the metal bowl with the gasses given off by the solution of Na2S2O5 and water.

Just a comment, and I am not sure it had an effect here, you mixed your solution about 33% stronger than is normal or recommended, i.e. most of us use 3 T to 1 gallon of water. I don't use Sodium Meta Bisulfite, rather I use Potassium Meta Bisulfite. In any case, I rinse any metal items immediately that come in contact with it with lots of water.

 

[Rice_Guy]

The food plant standard is to rinse all metal that contacts metabisulphite. It is very reactive and WILL damage any stainless where it sits.
This also goes for metal springs in spray bottles brass valves, jars with screw caps etc.

 

[Jim Welch]

Hard to tell without seeing it in person but looks like free iron. If it is it can be removed by passivating it which can be done at home by making a 10% by weight solution of citric acid in distilled water and soaking it. I have done this at home with stainless weldments I’ve done. It is time consuming using citric acid and it appears to be pretty heavy and might be easier to but a new one especially if the bowl is not a heavy duty bowl. I’d be inclined to replace it.

 

[Raptor99]

The gas released by Kmeta will condense to form an acid. It will corrode any metal to which it is exposed, including stainless steel. I learned the hard way when I had some Kmeta solution stored in a jar with a canning lid. Before long, the inside of the lid was corroded.

I store my extra Kmeta solution in glass jars with plastic lids. The spray bottle I use for Kmeta is rated to be used with acids. As @Rice_Guy said, it will eat away at metal springs, so regular spray bottles won't last long with Kmeta solution inside.

 

[winemaker81]

I store my extra Kmeta solution in glass jars with plastic lids.

Ditto. My LHBS carry plastic caps that fit the Carlo Rossi 4 liter jugs I use. I ended up throwing away all the original caps.

 

[Rocky]

Ditto. My LHBS carry plastic caps that fit the Carlo Rossi 4 liter jugs I use. I ended up throwing away all the original caps.

Bryan, the plastic caps that come on the juice bags in FWKs fit the top of a gallon, 3 liter or 4 liter jug perfectly. No need to buy them. (Yes, I am frugal.) Here are a gallon, half gallon and 3 liter with the caps from FWKs.

 

[winemaker81]

Bryan, the plastic caps that come on the juice bags in FWKs fit the top of a gallon, 3 liter or 4 liter jug perfectly. No need to buy them. (Yes, I am frugal.) Here are a gallon, half gallon and 3 liter with the caps from FWKs.


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Too late, I already have more than a dozen! But I will remember this. Thanks!