Originally Posted By TomJefferson:You are dead wrong.
If it was me, I'd use Citric acid. After cleaning real well through multiple rinses, I'd add a juice like lemon. You want the acid to over power what residue of the sodium hydroxide is left embedded in the plastic. A little lemon would leave a nice taste, compared to other household acids.
How much would depend on how well you rinse out the tanks. Rinsing method would be usual rinse and swish, but I'd also fill and then let sit, preferrably in the hot sun, for a few days, then repeat the whole process until there's either no basic pH, smell, or taste. Then I'd add the lemon juice with my water.
Keep in mind, unless the plastic is lexan, that NaOH will be in that plastic. Even if you rinse and neutralize if you store water in there, over time, it will leech back out of the plastic and increase the concentration of NaOH. Concentrated, that stuff is as bad as a strong acid and is very caustic. Not as bad as a petroleum product for safety but it would be high on my overkill list of things to be prepared for the worst. Thus the lemon juice.
Sodium Hydroxide will not "embed" itself in the plastic to "leach out later".
It is either neutralized, or it is not.
Regardless, the neutralized product of NaOh will be salt and water and some gas, no matter what acid chosen. None are cause for alarm, nor reason to use one acid above another for reasons other than cost.