I have been using Citric acid water mix for awhile and when I am done soaking parts I pump it back in 5 gal pails. I have noticed after a period of time it seems like maybe the citric acid drops out of it and crystallizes in the button of the bucket.
It still seems to work OK but, then it gets to a point where it will crystallizes on the parts while soaking. Its hard to get off and only seems to be of the top surfaces.
I maybe use it 4-5 times before this starts to happen
I clean oils off before soaking
I normally soak for 24 hrs @about 95 degrees
I have a pump that circulates it in the tank
I cant remember the mixing ratio (its at work)
Same thing happened with mine. It took a while for the crystallizing to start, but I just dumped out my first batch last week because it was really bad to the point that it pitted the parts. To be fair, I left them in there for way too long, but that stuff was hard to get off.
I made a new batch, because I still have plenty of the powder left, but I greatly reduced the amount that I added to the water. It still removed the mill scale very nicely after an overnight soak. I’m hoping the crystallizing issue was because the solution was oversaturated and the addition of other particles from the steel caused the acid to fall out of solution.
Not really. I just poured some powder into the tub of water. If I had to guess, it’s about 2 cups to 5 gallons of water.
My previous batch had much more, because I kept adding more to try to get the ph down. I found that the ph would only go down to a certain level no matter how much more I added
I was the same crystalization using. 12 oz. Roughly per 5 gallon give or take. I have made it stronger and weaker. I was buying it in 12 oz cans. Didn’t want to wait on delivery of big bags.
I really try to stay away from it .I had a large amount of brackets that this happened to. I backed them at about 450 til the stuff turned black. Then put them in a concrete mixer with blasting Media til the came off.
Any of you ever tried testing the pH of the solution?
Likely would be a very helpful benchmark to figure out if your mix is right or if your solution is lost potency or gain concentration through evaporation over time.
I have never tried to test the PH. Right now I actually am using a Ricky rigged concoction. I know it’s not the greatest idea. I needed to bath some stuff my vinegar solution was a little weak so I added a little citrus acid to it…. We do it canning so no danger.
As for evaporation it would probably happen during my soaking. I store it in sealed buckets. I normally bath a few days at most but sometimes a little longer depending on what going on. The longer soaks is where I saw the crystalization happen.
I know the citric acid is cheaper my opinion the vinegar is the is the way to go. I need to check into cost after making my own .
The next question. I have never noticed this with a fresh mix. What the chance this is a chemical reaction where the citric acid is being replaced slowly?
Well I asked our old friend ChatGTP and found some things to try.
I was using a wash thinner to clean oils off before soaking and she said not to do that. Use a Alkaline cleaner like simple green or maybe even dawn dish soap.
Also stay away from long soaks 20-45 mins
add 10-20 drops dish detergent to act as a surfactant
If reusing mix let it sit to allow the crap to settle out, use a paint strainer when reusing.
Agitate and 120 temp
mix = 10oz per gallon
Long soaks will cause the problems we are having and using it to many times.
I am going to change things up and see what happens
If you have time, go in and ask AI about it. Was pretty interesting reading
Let us know if you can confirm a remedy. I never saw the crystalization in the bucket when storing. The few time I saw it it would be on my parts and definitely over soaking involved. I don’t believe evaporation was a factor in these cases. I also use a way weaker solution than 10 oz per gallon.
I bet the crust in the bottom of the bucket was 1/8-3/16" thick. But from what miss AI told me a lot of that fall out could be from soaking to long. I will be mixing up a new batch and try to remember to check back. Remember we are talking about my memory here!!!
A overnight soak and it will spray off with a water hose when fresh. Doesn’t stay potent long I don’t think.
As for issues I can’t tell you a honest answer. The first major problem I had was when I left a bunch of parts in in for a couple weeks. I didn’t need them and was used to doing it with vinegar with no issues. The second time I was soaking some parts and got busy for a week or so and couldn’t get back to them.
Best case scenario I guess would be to start with a few small batches at different strengths and see cleaning ability and with adhesion starts… I know being busy it hard.
Wish I had better answers.
The residue after pickling the metal is the salt of the removed scale. Usually, it stays in solution until the liquid is saturated with it. It needs to be removed from the bath as it can interfere with the cleaning process, because it can deposit itself back onto the metal you are cleaning disfiguring the finish.
It normally doesn’t happen when the acid solution is weak because the acid is depleted before the salt saturates in the water.
That’s a great explanation. Overall that is the reason I only use it when I need a large quantity. I have never seen this happen with vinegar even leaving parts soaking for a week or more.