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Sodium Hydroxide vs. Potassium Hydroxide: What is the difference?

Sodium Hydroxide vs. Potassium Hydroxide: What is the difference?

(Pages 14-15 from the April 2012 issue of eClean Magazine)

Download the pdf: Sodium Hydroxide vs. Potassium Hydroxide

By Linda Chambers, Brand & Sales Manager, Soap Warehouse, www.SoapWarehouse.biz

For the kitchen exhaust cleaning contractor, almost any cleaner you would want to use on the market today will be based on one or the other of these chemicals, or be a combination of the two.

You need to understand their differences, pros and cons, to be able to best choose a product to fit your needs.

Sodium Hydroxide (NaOH) and Potassium Hydroxide (KOH) are almost interchangeable. They are the most chemically similar of the hydroxides. They are both a white, strong alkaline, corrosive solid or powder. Sodium Hydroxide is more commonly known as lye or caustic soda where Potassium Hydroxide is known as potash.

Both are used to change fats into soap in a process called saponification. Even though their solubility in room temperature water is about the same, products made with potassium hydroxide exhibit a greater solubility, especially as you increase the temperature of the water. Like all strong bases, the reaction of both Potassium Hydroxide and Sodium Hydroxide with water is strongly exothermic; in other words, they generate heat and give off hydrogen. But the reaction with Sodium Hydroxide is slightly more exothermic, which can make up for other more positive factors that Potassium Hydroxide possesses.

The biggest difference between them is in cost because of certain factors, such as their production process by electrolysis, where potassium chloride costs more than sodium chloride (table salt). In ton quantities, potassium hydroxide is about three times more expensive than sodium hydroxide.¹
At the molecular level, potassium hydroxide is also slightly smaller than sodium hydroxide; therefore, it can penetrate oil molecules faster than sodium hydroxide, thus breaking the oil’s hold on surfaces quicker. Since they are also more soluble, the oils can be rinsed away easier, especially when using hotter water or steam equipment.

If you need to clean a metal surface that is coated with a hard baked-on oil or grease, you would prefer to use a potassium hydroxide with a hot water rinse. A coating of thicker or softer oil or grease could be cleaned by using a sodium hydroxide for less of a cost with lower temperature water required because of the better exothermic reaction.

Using a product that contains both chemicals is like getting the best of both. You will be getting a lower priced product with a better exothermic reaction than with Potassium Hydroxide alone, but you will have a faster penetration and better rinsing product than if it just had Sodium Hydroxide.

Linda Chambers is Brand & Sales Manager at Soap Warehouse where she has worked since 2007. Linda enjoys writing articles for industry publications, blogs and social media. She also travels for the company exhibiting at trade shows and events. Visto the company’s website at www.SoapWarehouse.biz.

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