neilfj, thanks for comments.
I realized that 80-85º was higher than optimal, but with daytime temps reaching 95º, that’s the temp that liquids in the garage seem to have equalized on. And the anodizing instructions say that higher temps result in more open pores giving better dye absorption, which is what I’m mainly after, so I figured it would be OK. I’ve got plenty of heaters, but no chiller. Perhaps I’ll toss some food out of the fridge next time, and chill the electrolyte off overnight.
Regarding the connection, I believe it was good. Having lurked here for a while, I’ve seen all the posts about importance of good connections. Connection was made using an aluminum electrical breaker panel connector tightly screwed to the piece. Continuity both before and after the anodize was equal to or less than the resolution of my DMM (0.01 ohm). The piece was not fully immersed, but held up so the connection was above the electrolyte. Some electrolyte creep did occur, as seen by the dye along the edge of the connector, but never appeared to get between the connector and the piece. The square attachment area is finely delineated by the dye, and that area still has 100% continuity, so I believe it was good.
Voltage during the anodize time would seem to confirm this. When power was first turned on, voltage started at @ 1.4v, within a minute or so ramped up to @ 3v, and within 10 minutes had reached @ 6 v, then continued to gradually rise to the final 10v over the full duration. This seems to correspond to the curves in the LCD manual, and indeed the part did anodize. I was constantly having to stir the mixture to knock bubbles off both the piece and the cathodes. And interestingly, I could see the voltage drop a couple of tenths each time I did this, indicating that the bubbles were adding resistance.
The part took dye very well, so it did anodize, and overall I’m pleased that it worked this good for a first attempt.
The drying issue may be closest to the mark. I had not considered this before doing the test piece, and had noticed fast drying when I took the part out of the hot SP degrease solution. I tried to do the tank-tank moves and rinses as quickly as possible after this, not knowing what effect it might have. As you noted, the drying did occur around the periphery first. However, in my case, it never reached the main surface of the part, and I never noticed it spot up as in the photos.
I have to wonder about keeping it wet though. The spots and periphery areas are actually the BEST looking. They are bright and shiny with better color depth.
An interesting observation that I hadn’t mentioned earlier: the spots on the polished surface are horizontal to the piece, but the streaks on the blasted/brushed side are vertical, and run nearly the full length of the piece. This is difficult to see in the un-retouched photos, so I’ll do a few contrast enhancements to highlight it.
I’ll do another test in a couple of days, and keep the temp w/in optimal range, and keep the part thoroughly wetted.
Thanks again. Sean
|