I had been having my share of problems with red parts, and needed to get to the bottom of it. I had seen where one of the Caswell?s said the red PH has to be between 5.5 and 6. I had tried to use sulfuric acid without success sometime back, but apparently there were other issues. Lance Caswell confirmed that muratic or sulfuric acid was suitable to adjust the PH down, and ammonia is used to go up.
I didn?t want to risk spoiling a whole tank of red, so I used 5 paper cups so I could try several PH levels with a small volume of dye. I don?t have any buffer solution to calibrate my electronic PH meter. The base reading of the unadjusted red dye was about 7.5 with the un-calibrated meter. So, I simply adjusted each cup in PH from 5.3 to 6.3 (according to my meter) to test. I anodized a single small sheet of 5052 for 90 minutes at 4.5 amps per foot. I then cut enough test strips off the main piece, approximately ?? x 2?, and placed one in each dye cup. I also anodized the remaining sheet a little longer to compare the effects of anodize time also. Anodizing past PAR does make the color darker, and easier and faster to obtain, according to my tests.
The dye PH that did best, by a significant difference, was between 5.5 and 6., so I proved to myself that it is indeed important, and that I could adjust the PH successfully after all, and adjusted the main dye tank. The PH did climb back up after some time, and was adjusted again. I had suspected this would all work, because I had noticed if I didn?t rinse the sulfuric acid solution from anodized part very well, it would take dye well, but would bleed out if left in the dye very long.
Water PH will fluctuate, even when comparing distilled water from various sources, so it would be hard to sell a concentrate that guaranteed a proper Ph upon final mixing I would think. Plus, the PH of water will fluctuate when exposed to air, and I imagine other uncontrollable factors change it also.
Depending on the dye tank size, straight battery acid may be too concentrated because just a drop will change a couple of gallons noticeably and it may be hard to zero in on the desired PH with out going too far. So I diluted some battery acid in a 1:3 mix ratio with distilled water in a small eyedropper bottle, to more easily adjust the PH.
If you are having problems with red, adjusting the PH and possibly increasing anodizing time may be the answer.
The part on the left, was anodized @ 4.5-amp density for 90 minutes and dyed when the PH was high, in the mid to high 7 range. You can see some little dark specks, I have found that other times when dying doesn?t go well.
The part in the middle was anodized the same, but the PH was adjusted to the recommended range. Depending on the angle of light, the color may look lighter or darker than the part on the right, but is not as ?red?. The coating is thinner and it has more of a metallic look.
The part on the right was anodized @ 6-amp density for 120 minutes and dyed with the PH corrected dye. It is a true red, very solid and even with no imperfections, and the color is not as subject to vary with light reflection.
The picture isn't great, but hopefully good enough to help illustrate the differences.
I didn?t want to risk spoiling a whole tank of red, so I used 5 paper cups so I could try several PH levels with a small volume of dye. I don?t have any buffer solution to calibrate my electronic PH meter. The base reading of the unadjusted red dye was about 7.5 with the un-calibrated meter. So, I simply adjusted each cup in PH from 5.3 to 6.3 (according to my meter) to test. I anodized a single small sheet of 5052 for 90 minutes at 4.5 amps per foot. I then cut enough test strips off the main piece, approximately ?? x 2?, and placed one in each dye cup. I also anodized the remaining sheet a little longer to compare the effects of anodize time also. Anodizing past PAR does make the color darker, and easier and faster to obtain, according to my tests.
The dye PH that did best, by a significant difference, was between 5.5 and 6., so I proved to myself that it is indeed important, and that I could adjust the PH successfully after all, and adjusted the main dye tank. The PH did climb back up after some time, and was adjusted again. I had suspected this would all work, because I had noticed if I didn?t rinse the sulfuric acid solution from anodized part very well, it would take dye well, but would bleed out if left in the dye very long.
Water PH will fluctuate, even when comparing distilled water from various sources, so it would be hard to sell a concentrate that guaranteed a proper Ph upon final mixing I would think. Plus, the PH of water will fluctuate when exposed to air, and I imagine other uncontrollable factors change it also.
Depending on the dye tank size, straight battery acid may be too concentrated because just a drop will change a couple of gallons noticeably and it may be hard to zero in on the desired PH with out going too far. So I diluted some battery acid in a 1:3 mix ratio with distilled water in a small eyedropper bottle, to more easily adjust the PH.
If you are having problems with red, adjusting the PH and possibly increasing anodizing time may be the answer.
The part on the left, was anodized @ 4.5-amp density for 90 minutes and dyed when the PH was high, in the mid to high 7 range. You can see some little dark specks, I have found that other times when dying doesn?t go well.
The part in the middle was anodized the same, but the PH was adjusted to the recommended range. Depending on the angle of light, the color may look lighter or darker than the part on the right, but is not as ?red?. The coating is thinner and it has more of a metallic look.
The part on the right was anodized @ 6-amp density for 120 minutes and dyed with the PH corrected dye. It is a true red, very solid and even with no imperfections, and the color is not as subject to vary with light reflection.
The picture isn't great, but hopefully good enough to help illustrate the differences.

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