Alodine solution weak - Re-apply?

I've been doing a lot of small parts in a 3 quart batch of Alodine over the last two weeks. Last night I realized my parts didn't seem like they were taking on much color, even when I upped the time from 3 minutes to 8 minutes. I think I may have let too much light get to the Alodine solution and it has become ineffective.

Can I just re-etch those parts and then use a new Alodine solution to get a proper Alodine surface treatment?

I would test on an unimportant part (easily replaced).

Thoughts?

Dan

Just to be sure, you're using Alodine 1200 vs 1000?

Yes, Alodine 1200.

Dan

If your color has just weakened, then the solution is indeed getting weak. If you refresh it, then just put the parts back in to get a darker color. Be advised, that the color is different with different alloys. ALclad is 1100 for the surface.

You can also heat the solution to get better performance. I am up to 7 min as well on my 5 gallon dip bucket.

Just another point.

In my Alodine process I leave the parts in the bath between 45 seconds and a minute and that is sufficient to get the color I want. I use the solution undiluted that I purchased from Aircraft Spruce.

One additional factor besides the concentration of the solution is the surface roughness. The parts need to be cleaned and etched prior to alodining. I use AlumiPrep 33 available at ACS. I scrub the parts with the etch solution and a maroon scotch-brite pad. If the parts are not etched they don't take on the color very quickly and it can be very uneven.

Alodine

I use a different approach.
Since I'm down to little parts, I use heavy zip bags.
One for Alumiprep. One for Alodine. Only enough solutions to wet parts and slosh around. Maybe a couple tablespoons. They are usually good for several little parts for whatever job is in progress I have a couple rinse pans. Rinse goes into a haz mat bottle. Solutions end up in the bottle too when no longer active. Very little used.

Thank you for everyone's feedback. Since I originally posted I did mix up a new batch of alodine. Those parts that I thought were weakly alodined, I ran through the new solution for a little improvement.

I think where I made the best improvement, I used a new Gray 3M pad during the degreasing step (previously I had used the same 3M pad for 5-6 work sessions). I get the abrasion done during degreasing (I use POR-15 Cleaner Degreaser). Then the next day I etch and alodine. The parts I did last night came out great.

So my learning points:
1-I now store the alodine solution in its 1 gallon clear pitcher - that is inside an orange 5 gallon with a black lid and stored under my work bench.
2-I will change my 3M pad much more often to ensure the abrasion effect is in place and allow the etch & alodine to do their work.

Thanks for everyone's suggestions,

Dan