Brown Staining of Stainless Steel
Brown Staining of Stainless Steel
(OP)
We recently compounded a shampoo formula in a brand new stainless steel vacuum tank. All product contact surfaces are 316L. We introduced the high active surfactant into the batch with 80°C water as the disperser (through a shear mill). After the batch was completed, dropped and cleaned, we noticed multiple brown stains all over the bottom of the tank and periodically on some of the sides of the tank. The stains are smooth to the touch and do not rub off. We have passivated three times with a 20% citric acid solution, to no avail.
Does anyone have any insight into what these stains are and are they harmful to the stainless steel?
Thanks
Does anyone have any insight into what these stains are and are they harmful to the stainless steel?
Thanks





RE: Brown Staining of Stainless Steel
What is the water quality used?
How was the tank heated?
As you have found out Citric acid alone probably isn't going to clean the tank.
Two things to try. If you have a surfactant or wetting agent compatible with citric acid try adding a little to the solution. You might want to try citric acid again and if so get a proprietary compounded cleaner and use a directed.
You might also want to try H3PO4 based concentrated cleaner and dilute 3::1 acid::water. Assistance from a Scotch-Brite pad may help.
I would also test an alkaline base cleaner.
This is the long approach as you tank is new and pretty.
RE: Brown Staining of Stainless Steel
RE: Brown Staining of Stainless Steel
Could any of surfactant contact the hot surface sans water?
I think 60C is max at 70% and essentially the same before hydrolysis starts in solution.
As state new system was all part thoroughly cleaned prior to start up?
RE: Brown Staining of Stainless Steel
RE: Brown Staining of Stainless Steel
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Plymouth Tube
RE: Brown Staining of Stainless Steel
Mark Hutton