Will a film of oil on water retard evaporation (of water) and prevent air and atmospheric impurities from diffusing into it?

I vaguely recall hearing that a layer of oil on water will slow down the evaporation of water, as well as serving as a barrier that would prevent (or retard) the diffusion of air and atmospheric impurities into it. How accurate is this claim?


**Some Background:**


I want to make zinc/air batteries. $\ce{KOH}$ is commonly used in the electrolyte, but $\ce{CO2}$ in the air can react with the $\ce{KOH}$ and form carbonates which hinders the battery's performance. It seems like oil on top will shield the electrolyte from atmospheric $\ce{CO2}$. The $\ce{H2O}$ also must be kept from evaporating, which would otherwise result in changes to concentration. $\ce{KOH}$ is also very hygroscopic and tends to attract water from air which would also cause variations in concentration.


When the batteries get discharged, $\ce{ZnO}$ is a final product. This should almost certainly precipitate and collect on the bottom of the tank since its considered insoluble in water.


Solar panels harness a vast amount of energy from the sun during the Summer. Storing surplus enrgy for use in Winter is a daunting task. A method that's been doing rounds these days: One could collect and reduce the $\ce{ZnO}$ back to $\ce{Zn}$, deposit it on plates/electrodes, and store these plates for Winter use. The plates could be put back in the batteries and the electrolyte (a fresh solution of $\ce{KOH}$) would have to be replenished. 




I don't know about oil (fun fact, putting oil on water was a traditional approach to calming waves, thus the phrase ["pour oil on troubled waters"](http://www.phrases.org.uk/meanings/288150.html)). But cetyl alcohol has been used to decrease evaporation from reservoirs, which might be what you heard about. For instance, here is a [report](http://www.twdb.texas.gov/publications/reports/technical_notes/doc/TechnicalNote15-01.pdf) on this, with lots of references. They used a mix of steryl and cetyl alcohols (long-chain alcohols that will form a monolayer on the water).


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A oil film definitely slows down evaporation. For example, when the [meibomian glands](https://en.wikipedia.org/wiki/Meibomian_gland#Clinical_significance) don't work properly, there isn't enough "oil" in tears, and people who have a problem with these glands are subject to dry eyes.


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