Semi Cleaned Coins

You've done a good job, clean and the patinas are still intact - I think your probably finished.

Some of them look pretty good, on to the attribution now

It is good you are endevouring in the coin cleaning and discovery process.
Below is my opinions, of what I see.
When I started, years ago, uncleaned coins were the first and easiest Roman coins for me to get, most were very low grade copper slugs, a few were okay, one was a gem.
So, I've done a lot of this in my experience.
The positive is that now know not to make those errors if I get an uncleaned coin.
Most of all, be patient & AVOID ELECTROLYSIS.

#1 Valens, a copper coin, nothing more to clean.
#2 Constantine II, nothing more to clean, the danger now is of removing the patina.
#3 Aurelian, the original silvering has corroded into "horn silver", basically it is a black, flaky build up. If you try to clean the result will be a pitted AE (bronze) surface.
#4 Valentinian I, (good example) no more cleaning needed.
#5 Gallienus, a Centaur/Sagiterius on the back, perhaps a little cleaning around the Radiate crown. By his reign, the Antoninianus had only about 15% silver to it.
#6 Urbs Roma, do not clean, as the patina seems to be wearing off, as has happened on the reverse.
#7 Constantius II, though some corrosion remains, the choice is remove it and have a very pitted coin or leave it. It seem to be an Official Issue, from the Siscia mint, and is common.
#8 Constantine I, Siscia mint, leave as it is, the soil dirt highlights the features.
#9 Constans, leave as it is.
#10 Constantine I? Obverse fine, reverse overcleaned.
#11 Gratian? Copper. Some black encrusation is seen on the obverse. Maybe a soak in a salt-water solution in a jar/small container might work off that encrusation, anything acidic will corrode the coin.
#12 Cannot make out the obverse legend, ....STANTIS...? Obverse okay, reverse overcleaned.
#13 Constantine? Obverse overcleaned, reverse a light clean needed, nothing abrasive.
#14 A plated denarius of a young Marcus Aurelius? Cannot be cleaned as it seems corroded.

Just to reply to the over cleaning comments. The only method of cleaning that I have used is distilled water and brushing with a kitchen brush. I take it you can overclean using these methods.

Well I can only assume that the coins in question were already in that condition.
These grades of coin often have a fragile patina to start with.

Steve - you'll some people say that as soon as a full ID is possible, the coin is clean. I personally dont htink so. When I stop cleaning is when I feel that further cleaning would detract from the coin (i.e. destroy patina,remove dirt highlighting the features, remove character). Personally, I have over cleaned many coins - but they are mine and I have no intent to sell most of them so I clean them to the state I want them in.

If silver appears on a bronze coin you've overcleaned it with acid. If a bronze spot appears the patina is breaking off. Ovften the patina is very very weak - I've lost very nice and possibly valuable coins to this.

Q. "What should I do with that last coin?"

A. Put it in a box marked "culls." I have one, it has lots of yucky culls in there.

I remember reading something last night. I believe it was 250 for half an hour? I've never done it.