I dont think you missed much, other then the approx. time you think it will run at 1:2 ratio with 12ASF.
Im getting the same end result SOMETIMES as I have complained about in the past. I hazey film over the parts. Sometimes you can wipe it off with your fingers or hand buff off with a papertowel, sometimes you cant. Sometimes you get spots on the part that have no haze and are much glossier then the rest of the part, even after you remove all the haze. I get that symptom, OR the parts simply dont dye very deep. I dont think it has a sufficient layer of anodizing on it. Parts are cleaned, desmutted, and pass water break test before ano. Everything is rinsed between each step. Maybe its my connections, maybe it isnt.
1. Bath temp. 70-75 deg. F..
YES
2. Al or Pb cathode, at least as large as the work.
4 8X8 lead/GP plates. My normal large batches are about 140-200 sq. in.
3. You are using CC anodizing, or at least really measuring the current.
Using CC
4. The alloy you are anodizing is 6061 or 6063? We need to know.
6061 and 2011. The 6061 usually turns out better.
5. At 12 ASF and with 1:1 electrolyte, you anodized for 30-45 min., under these conditions, anodizing longer will cause dissolution problems.
I think thats what may have been happening. I think it was hitting PAR at about 30 minutes.
6. Exactly what are you using for a rectifier?
Mastech 20amp/30V CC/CV PS.
7. What is the surface area of the work?
My normal large batches are about 140-200 sq. in.
8. What is the connection method to the work? Since you are troubleshooting you should go back to soft Al wire and Al bolts.
Ti racking now. Used to randomly get same results with Al wire connection too. I simply can not use bolts.....I cant drill holes in the parts being anodized. The Ti almost has to be making a better connection then rigging the Al wire up to the parts.
9. How are you cleaning and removing native oxide from the work?
Caswells stripper. Then parts are polished and cleaned.
10. You have properly measured and mixed anodizing dye; if its red (at least) you did measure and correct the pH.
I measured the Ph when I first mixed it, and it was off from what Caswell said it should be. I got some parts that dyed fine in it, so I become less concerned about the Ph.
11. You dyed at 140 deg. F. for at least 20 min. longer doesn't hurt.
I try to keep dye temp 130-140. Dyed the last batch at 30 minutes just to get a semi-deep red.
12. What is your sealing method?
Caswells sealant(stuff that comes with kit). I can get the same bad results without sealing or with sealing the parts, so I dont think sealing has anything to do with it.
13. You have sufficient agitation in the anodizing tank.
Id like to think so. I have two high output fish tank pumps running into a PVC grid at bottom of tank. It creates a fair amount of agitation.
14. Your electrical connections are good (all of them). I've been a practicing EE for 30 years and I can't tell a good connection from a bad one just by looking at it. Some voltage vs. current measurements would help a lot.
Last batch....143sq.in. ran at 13.5A(12A for the parts and added an extra 1.5A for the Ti racking).
Voltage/ Time:
1 min/ 13.0V
26min/ 10.6V
30min/ 10.1V
40min/ 9.4V
44min/ 9.2V
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