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Chemistry question for ASTM B117 pH levels

I'd like to run a few questions by the chemists out there who are familiar with ASTM B117. I am preparing to run the B117 salt fog test, and just yesterday found that I am out of sodium hydroxide to increase my pH levels in me reservoir. I'm 12+ years removed from chemistry class, so after a quick refresher found that Baking soda [in bulk on eBay or Amazon [affil links] (sodium bicarbonate) is basic and would theoretically work to raise the pH. With respect to the B117 spec, is this an acceptable alternative?

As I understand it, a salt solution of NaCl and water will allow for the development of HCl acid by spare H ions. Mixing sodium hydroxide (is that NaOH? not sure)with the solution will neutralize the acid and give off H20, NaCl, and CO2. None of these would be considered contaminants in the solution. Am I on the right track?

If I mix sodium bicarbonate, I'd get H20, some type of "carbonate" salt and C02. Would the "carbonate" salt be considered a contaminate to the ASTM B117 spec? Would this "carbonate" salt give significantly different corrosion characteristics than NaCl?

I like that sodium bicarbonate is cheap and easily attainable at the corner grocery store, so I'm considering using it as an alternative if acceptable. Can I do this or am I getting myself in trouble?

Alan M. Polaski
- Waterford, Michigan
2007

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Alan, to do it by the book, buy the 'book,' ASTM B117.
Only ACS reagent grade HCl & NaOH solutions are permissible for pH adjustment. The pH of room temperature salt solutions may rise when heated due to loss of CO2 gas.
Purity requirements for the salt and water are also given. See letters #10548 & 40610.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2007

When I was employed at a government owned testing lab supporting industry I followed ASTM B117 to the letter after all the results were certified. In industry a lot of little short cuts are taken such as yours. Most have little if any real effect as most testing is for comparison QC purposes and for internal use only.

Ronald Zeeman
Coil Coating - Brampton, ON, Canada
2007