Home Cosmetic Science Talk Formulating Preservative get brown

  • Preservative get brown

    Posted by Dilfre on August 23, 2016 at 11:14 pm

    At my company, we have been preparing a blend of preservative in plastic recipient. the formula is:

    44% Etanol 96% 
    24% Benzalconium Cloride 50%
    24% Sodic Methil Paraben 
     8% Sodic Propil Paraben

    Recent preparation was done in big stainless steel recipient, due to quantity to be prepared. A small amount remain in the recipient 12 hours and get colored and the metal show small brown spots. I’m not sure what reaction causes the color. I will appreciate any advice in this matter. 

    Aditional question is if there is any interaction between components of the formula. Thanks again.

    Dilfre replied 7 years, 9 months ago 3 Members · 5 Replies
  • 5 Replies
  • belassi

    August 24, 2016 at 12:15 am

    Your “stainless” … isn’t.
    Ask the supplier of the container what specification the steel is.
    Try leaving a sample of the Benzalconium chloride in contact with the container.
    The passive layer on stainless steel can be attacked by certain chemical species. The chloride ion Cl- is the most common of these and is found in everyday materials such as salt and bleach. Pitting corrosion is avoided by making sure that stainless steel does not come into prolonged contact with harmful chemicals or by choosing a grade of steel which is more resistant to attack. The pitting corrosion resistance can be assessed using the Pitting Resistance Equivalent Number calculated from the alloy content.

  • belassi

    August 24, 2016 at 12:20 am

    I hate to say this but I believe you are going to have to change the vessel. Retire that one to some such use as mixing shampoo. Even then you will need to passivate it.

  • Dilfre

    August 24, 2016 at 8:57 am

    Thank you Mr. Belassi, your advice is very useful and appreciated.

  • OldPerry

    August 25, 2016 at 12:52 pm

    I agree with @Belassi - I’m guessing a reaction with the Benzalkonium Chloride and the metal in the pot.

  • Dilfre

    August 25, 2016 at 5:14 pm

    THANKS with capitols Perry for make this interchanges possible.

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