Aluminum and Vinegar

[dcoyle]

I have learned an expensive lesson about aluminum and bleach. After removing the aluminum waste holding tank pumpout pump for rebuild I cleverly decided an overnight bath in hot water and bleach would be beneficial. Much to my surprise the next morning my pump did not look to good, found out aluminum and hot bleach are not happy when together.

I have been adding a couple of gallons of white vinegar occassionally to help keep system odor down, now I`m wondering if the vinegar attacks the aluminum pump. Any chemical guys know?

 

[tenders]

Well, you always have to be super-careful with bleach. Bleach is a highly corrosive caustic material while vinegar is weakly acidic: different elements altogether. A couple of drops of bleach per gallon of water in the tank will do much more good than harm (in fact, with iffy water, this is often recommended). Likewise, a rinse of vinegar isn't a bad idea for a lot of things.

Under no circumstances would I combine bleach with any other cleaner. When I lived aboard at the Long Beach Naval Station in the early 1990s, someone several piers down from me died while cleaning his boat with a combination of bleach and ammonia. I don't know what the resulting chemical is (hydrochloric acid vapor perhaps?), but he asphyxiated himself with it.

 

[u079721]

As our resident chemist I should probably chime in here.

Good advice about NOT ever combining bleach with any other cleaner. If you combine it with ammonia you make not chlorine gas (as is incorrectly but commonly assumed) but rather chloramine gas. Doesn't make much difference what you call it though, as you will be just as dead. My own wife did this one time and I had to rush her outside to get some fresh air.

I've not ever heard of vinegar - which is quite dilute acetic acid - hurting aluminum. In fact, a common suggestion for removing the discoloration of aluminum cookware after it is sometimes darkened by washing with harsh detergent is to boil water and vinegar in the pot. But I would not do this for long, as it can eventually pit the surface.

The problem with bleach and aluminum is not the bleach part but rather the alkalinity. Bleach (sodium hypochlorite) is not only a strong oxidizer, but pretty darn basic, meaning it's like adding lye, or strong base such as sodium hydroxide. And in case you didn't know, the bubbling action in traditional Drano drain cleaner comes from the reaction of powdered aluminum with sodium hydroxide. So if you put an aluminum part in strong alkali (such as bleach) for long enough the whole dang thing will dissolve. (I saw this happen one time back in graduate school - very embarrassing.)

And as mentioned, the thing about bleach in aluminum tanks is that it is OK to use a few capfuls on a normal basis, and maybe even a couple of cups for a BRIEF shock treatment - but do not go pouring a gallon of bleach into an aluminum tank and leave it overnight. You can get away with that (even if it is overkill) with a poly tank, but the aluminum tank will eventually pit right through.

 

[dcoyle]

Thanks for information. Since the pump was the waste tank pumpout and looked pretty nasty after all those years thought bleach would be a good thing. Unfortunately the outer finish peeled off and the inside got coated with some white residue. also the discharge port got all pitted up. Found a new unit on ebay that was several years old, but unused $133. I was concerned that perhaps vinegar was adding to the damage. Sounds like it still save to use. No vaper trails behind this boat!!