Letter 26056

Effect of caustic gel on food grade stainless steel? [Canada] 

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Hi.

I run a small kitchen exhaust cleaning co. and have been asked by a customer if "using caustic potash(Sodium Hydroxide) on the food grade, stainless steel canopy to strip the grease from the surface will also remove or reduce the finish of this expensive surface?" We apply this in a gel form and then after apprx. 20-30 mins rinse it off (never leaving any white streaks when dry). Could we be doing any damage.? What about over time? Say 4 cleanings per year?

Thank you,

David Patterson
Kitchen Exhaust System Cleaner - Mississauga, Ontario, Canada

You should not be causing any damage to the steel hood covers (usually the grades that lend themselves to forming are also fairly compatible with NaOH). Example: We use a 3% Na-hydroxide in a food-grade stainless steel container heated to 50°C. This is in continuous use with no corrosion problems. (It has "stained" where the carbon content , but that is very limited, and no leaks or functional problem has resulted).

Some staining may occur depending on the grade and the concentration of the cleaning solution, but it sounds like you are using a low % and room temp, so it should not be a problem.

In dealing with these type problems, the first step is to verify the grade of stainless (or other metal), then check a materials compatibility guide to make sure that it is compatible with NaOH (or the chemical to be used).

Douglas Corbett
circuit boards - Salt Lake City, UT, USA

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