Why did a jar of vinegar destroy this metal lid and turn it black (see pic)? About a month ago, I filled a thoroughly-cleaned-out glass salsa jar with vinegar and hand-tightened the lid. Specifically, I filled the jar with generic white distilled vinegar ("diluted with water to 5% acidity"). I did not open the jar between now and then. 

Today, I opened the jar, and I couldn't believe what I saw. The inside of the metal lid has been destroyed, filled with clumps of abrasive, black particles that are firmly attached to the lid.

The inside of the lid also has some rust, which is even more odd, because I thought that vinegar removes rust.

The jar was not even all-the-way full. This is the vinegar jar in question:



This is what the lid looked like a month ago, when the jar was empty:



This is what it looks like today:





I have two questions.


How on Earth was this metal lid destroyed by the presence of vinegar?
What container material is best to store vinegar for long periods of time, without deterioration?


I purchase vinegar in a gigantic plastic carboy, because it is cheaper in bulk. I would like to have the vinegar available in a smaller container. I prefer to use a type of container that's recycled from a common item (like salsa).

Note: Not that it matters in the context of my questions, but I'm not actually using this vinegar for cooking. I use it as a safe disinfectant for items such as a retainer. Given that vinegar is typically viewed as a food, I thought that it would be appropriate to pose this question to Seasoned Advice.
Vinegar is an acid and acids are not stored in metal, it eats them.  Some are less reactive, like stainless steel, but still not a good idea.  Normally plastic is fine, that is what vinegar is often marketed in, but glass is usually best as the main container, but lid should either not be metal or should be fully and well coated, and I would tend to avoid that as well unless I knew it was non-reactive.

An option for ready use would be a glass decanter, as used for oil and vinegar dressing.  These often include a glass stopper, so they make a good but spill prone option.  For longer term storage, my choice is a wine bottle and cork.  The corks (including the synthetic ones and even the twist on) should all be designed for a similar environment to vinegar.  Lower acid but longer term so the same general effect.