I plan on making a very simple cleaning solution to clean metal contacts on PCB boards. It cannot contain anything that is flammable or hazardous so I've come up with the solution below.
- Distilled Water ~92%
- Ethoxylated Alcohol (CAS 68439‐46‐3) ~5% "surfactant"
- Tetrasodium Glutamate Diacetate (CAS 51981-21-6) ~1% "chelating agent"
I am not making this solution in a perfectly sterile environment so I would like to add a preservative to increase shelf life. I've been researching for weeks and I cannot find anything definitive. I just want something that will easily dissolve into the solution above and not be harmful to metal. The solution will be applied to the metal via a cotton swab. Even if I find a suitable preservative how would I go about calculating how much to use?
My ideas for preservatives: I think Citric Acid (CAS 77-92-9) would be okay. I think a combination of Methylchloroisothiazolinone (CAS 26172-55-4) and Methylisothiazolinone (CAS 2682-20-4) would be okay as well.
Other concerns are: Do I need an emulsifier? Is there an additional non-hazardous chemical I can add to decrease drying times?