[RVFan671]

I've got about 1.25 gallons of alodine which is in a flat container I use in my acid etch and alodine process for my parts. The 1.25 gallons is getting a bit wore out in that the parts are not as golden hue even after they've sat in the solution for 5 minutes or so. So I bought a new fresh gallon. Would it be best to (safely) dispose of the old 1.25 and start fresh or add the fresh 1 gallon to the existing 1.25 so I've got a deeper bath that will be a little weaker then new alodine?

 

[RV6_flyer]

I've got about 1.25 gallons of alodine which is in a flat container I use in my acid etch and alodine process for my parts. The 1.25 gallons is getting a bit wore out in that the parts are not as golden hue even after they've sat in the solution for 5 minutes or so. So I bought a new fresh gallon. Would it be best to (safely) dispose of the old 1.25 and start fresh or add the fresh 1 gallon to the existing 1.25 so I've got a deeper bath that will be a little weaker then new alodine?

Start FRESH.

Adding will just dilute the solution to be something between the old and the new.

 

[FlyHigh]

I would start fresh so you know where you stand. They do make test strips that you can check the quality of your alodine.
Keep in mind that different alloys take the alodine gold color differently. You can have 2,3 or 4 of the "same aluminum" and they each may take the alodine golden color differently, sometimes, there is no color change at all.

 

[chaskuss]

Alodine and it's competitors do weaken with use. If having additional volume will aid you in treating larger parts, add the new Alodine to what you already have. Otherwise, dispose of the old stuff and use the new. Since this solution is nearly all water, when I need to dispose of it, I leave it outside in the summer heat to evaporate as much of the water as possible. That way, you have less to dispose of.
FYI, This is VERY important. NEVER do Alodining out in the sun. This stuff is photo-chemically reactive. It will work just fine the first time, then be ruined. A friend ruined 5 gallons of Iridite [Alodine competitor] doing this. To save money, you can buy 10 pounds of Iridite in powdered form. It looks like freeze dried coffee crystals. This will make over 100 gallons of liquid Iridite. Many years ago, I arranged a group buy of 10 pounds of powdered Iridite. I kept enough to make 30 gallons [I had 1 piece main wing skins] and sold the rest to fellow VAF members. At that time, the end result was that each gallon of Iridite made from the powder cost under $2.

 

[wirejock]

Agree. Start over. Dispose of the old.
I collected every drop of the Alodine, Alumiprep and the rinse. I used a sluce into a storage bin. It was left in a safe place outside to evaporate with a screen to keep animals out. Once it was managable (1 gallon), it was transferred and disposed at the haz mat disposal.

 

[scsmith]

PLEASE dispose of the old Alodine properly, I.E. take it to a HAZMAT place.
Alodine is hexavalent Chromium, which is one of the most harmful substances there is, next to maybe dioxin and plutonium. Just ask the residents of Hinkley, CA.

Many aerospace companies no longer use Alodine. Instead they use AC-130 Solgel, which was developed by Boeing to be an environmentally friendly, safe-for-workers, replacement.
We use AC-130 Solgel followed by BR-6747 epoxy primer.

 

[Freemasm]

PLEASE dispose of the old Alodine properly, I.E. take it to a HAZMAT place.
Alodine is hexavalent Chromium, which is one of the most harmful substances there is, next to maybe dioxin and plutonium. Just ask the residents of Hinkley, CA.

Many aerospace companies no longer use Alodine. Instead they use AC-130 Solgel, which was developed by Boeing to be an environmentally friendly, safe-for-workers, replacement.
We use AC-130 Solgel followed by BR-6747 epoxy primer.

Chrome 6 never leaves the environment, including your body.

Where do you buy your mentioned products. A quick search didn't reveal a source that sells to the public.