Questions after first run

[cameraman]

I did my first successful run yesterday. It dyed beautifully so I take that as a sign that it also anodized beautifully. It was a bit of a rocky go, however, mostly because I made (ahem) improvements to the process. This is long because I know that the more completely and accurately my description, the more likely you veterans will be able to see what went right and what went wrong.

Not wanting to cut a 1/4" strip in my perfectly good new cathode plates, I instead bent the end of the titanium wire into a loop, drilled a hole in the corner of the plate, put the wire up against it, and covered it with a strip of aluminum on both sides with matching holes. On one plate I secured it with an aluminum pop rivet and on the other with an aluminum bolt & nut. I figured that the aluminum hardware would at best anodize and become essentially inert and at worst dissolute into nothing (taking several months to do), but since the wire was up against the lead, the state of the hardware wouldn't be an issue.

The part was a flat aluminum bar very similar to the practice pieces which ship with the kit. The bar has a hole near each end, so I attached the other titanium wire to it with an aluminum bolt and nut through one of the holes.

The bar is 25 sq in. I figured 4.5 amps/ft² with .7 mil thickness, so that's .78 amps for 112 minutes with peak voltage of 11.25.

When I turned everything on, the power supply decided on 3.5 volts. I noticed that I was getting bubbles at the anode connection and both of the cathode connections. After letting it sit that way for a half hour or so and not seeing the voltage change by any significant amount, I began to worry that I was anodizing hardware and the target piece was just along for the ride. So I lifted the piece until the connection was up out of the solution. The voltage went up to around 10 volts. The hanging hole is very near the end so the surface area was reduced by absolute max of 2 sq in.

After a bit more (30-40 minutes), I began to wonder if my (ahem) improvement might be impeding the process, so I suspended the plates so that those connections were out of the solution as well. Now the voltage went up to a little over 11.

I hadn't stopped my stopwatch while making the modifications. I had cut the power each time. Lifting the part was simple enough, and it didn't come completely out of the solution. When I adjusted the plates, I did remove the part completely from the solution and hung it out of the way. I guessed that I probably spent about 10 minutes rigging the plates, so when I turned power back on I left it in for another 50 minutes. During that time, the voltage very slowly but steadily dropped, which completely flummoxes me. The way I'm understanding it, the voltage is supposed to increase to PAR, then when optimum thickness is reached the current is supposed to drop.

As I said at the beginning, I got a beautiful dye out of it. It's not completely uniform (the edges look a little darker than the middle of the length) but it looks like I must have had a sufficiently thick layer. There's also a soft line of lightness going diagonally across on both sides of it. On one side the line's low end is about 1.5 inches from the bottom end of the bar and ends up 2.5 inches from the end. On the other side, it starts at about 2.5 inches and climbs up to 3.5 inches. Since the dye mixes up at 2 gallons, I stuck the 11" long bar in at an extreme angle. I didn't particularly want the 'hung' or upper end in the dye because it had a black oxide band where the acid solution had lapped against it during anodizing and I didn't know whether or not that would contaminate the dye. I had the heater suctioned to the side with its top just below the surface, so I'm wondering if those lines correspond to the bottom of the heater, where the temperature might have started dropping off - however, there's dye on both sides of the line, so I'm puzzled. The lines aren't ruler straight - there's just a hint of curve to them - and they're very soft sided. They're thin - no more than a millimeter. I'm spending so much time describing them because I'd actually like to duplicate it or something similar. I read about fades and such but I can't begin to imagine how to accomplish an effect such as this intentionally.

I'm normally pretty precise and prefer as close to perfection as I can reasonably expect in things, but when this bar came out of the dye it occurred to me that it bordered on art and gave me a whole new perspective on how my product could look.

So I'm trying to figure out what went right and exactly how badly was I messed up in my thinking during the whole thing.

1. Are bubbles coming off the mounting hardware ok and can be ignored? Is it the water breaking into hydrogen and oxygen, or is some of the hydrogen coming out of the acid?
2. Is it ok to have the cathode connection down in the solution or do I really need to grit my teeth and snip a strip?
3. Is it ok for the part's titanium to be in the solution or do I need to use aluminum up to the surface and connect the titanium above?
4. Was I getting any anodizing action before making one or the other change, or did it all happen in that last 50 minutes?
5. How can I intentionally make soft-sided imperfections like the lines I described?
6. I sprayed the sealed part with wd-40 as instructed, but why did I do that? When can I wipe it off?
7. How do I know when chemicals need to be replenished? I understand the bit about replacing evaporated water, but do I have to wait for crappy parts before figuring out that the de-oxidizer needs to be replaced? How do I know when the sealant is dead? If the bubbles in the ano tank are just water hydrolizing then I can figure that the acid's presence is largely catalytic except for the small amount that migrates into the neutralizer tank, and as the dye lightens that's pretty apparent, but those other two... And mist suppressant - will mist begin forming and then I add a couple more teaspoons?

Thanks for taking the time to actually read through all this, and Caswell, I'm sold man, I'm sold.

[acidrain]

Well, I don't ano with titanium wire, so there may others more educated in that area, but I do know that as long as the wire is firmly attached with an aluminum machine screw, the wire and hardware can be fully submerged.
As for your cathode, I have my lead plate connected outside of the acid, and suggest the same for you.
I am very experienced with streaked dyed finishes.... that affect can be caused by several reasons. Here are a few, and see if any of them sound familiar:
Acid can be trapped at the connections, and will slowly leach during dyeing and cause a streak.
Shadowing is caused by the current being blocked from an adjascent part, or non-uniform placement of cathode to anode.
Contact with buckets, and other parts after ano will often cause non-uniform dyeing. I learned the hard way early on that you have to suspend your parts in the rinse bucket, dye, and sealer pot. Be mindful not to allow parts to rest against each other, or the sides of the bucket or container.
Hope that helps. Sounds like you are on your way.

[sswee]

I'm with acidrain on the cathode connection. It needs to be out of the solution. Have you thought about turning the cathode on it's corner, fold the corner you drilled the hole in over the edge and bolt your connection there. Most of what you described sounds like a weak or bad connection in the circuit. From experience, your voltage should rise a little rapid for the first ten to twenty minutes then slow up for the remainder of the run if your electrical connections are good.
Most of the chemicals degrade very slowly with the exception of the sealer. The most noticable thing with the sealer is the clarity and color. The other chemicals show more in effectiveness. As long as you don't get contamination, they will last many months to years. Hope this helps. SS

[cameraman]

Thank you both for the info.

I've done four runs now. The last three have all been with the cathode connections up out of the solution. They dyed much darker than that first run so it must have a thinner layer, likely only 'really' anodizing in the last 50 minutes.

The voltage did the same thing on the 2nd and 3rd runs. Before doing the 4th, I noticed that the wire was looking a little brownish where it had been submerged so I scotchbrited it. The 4th run was a piece identical to the one for the 3rd and finally the voltage acted as sswee described, although my peak was 9.6 volts (I'm running the same, 4.5 with .7 mil). I hadn't done anything to the wire previously, so maybe it came out of the package a little oxidized.

acidrain, I'm pretty sure I didn't have any of those problems - it was the only part in the tank and actually wobbled around a bit from the agitation, so I don't think it was any sort of shadowing. The connection was at the other end from those two lines, and I was extremely careful to not touch the part to me or anything else during the whole process. The most likely answer I can come up with is maybe some sort of contaminant that didn't come out during degrease or de-oxidize. When I did the water break test I didn't dunk the part, just dribbled some in several spots.

Those give me a good start on things to try to encourage some non-uniformity, though. Intentional shadowing sounds very interesting, although it could be tricky to affect the layer just enough to cause a color shift without compromising the function (my primary goal is corrosion resistance).

Has anyone tried RIT dyes? I would like to do a cyan but it doesn't look like I can get there with the Caswell dyes & color wheel.

[sswee]

New wire could have oxidation or it could be some sort of coating. The calculation for peak voltage is just that, a calculation. It is fairly accurate when everything is right. A little off is not much to worry about. It's when it is way off , there is a problem somewhere.

I've read that some guys using Rit did ok but was not color fast. I myself did not have any luck with it. No consistency and never the color I was trying to get. The cost is not much different. Just my experience.

Sounds like your on your way. Let us know how it goes. SS

[M_D]

The peak voltage will vary according to several factors. Connection quality, current density, acid concentration in the electrolyte, and electrolyte temperature and perhaps most important part temperature. If the voltage drops below the normal expected range, it could likely be the agitaion is inadequate and the part getting warm decreases the require voltage to maintain the amps.

The variation in color like seen on your part can happen because of factors like acidrain mentioned, and they can happen for other reasons too. One is getting contamination on the part surface after anodizing properly, which can mask the mark and inhibit or prevent dying. We have seen the soda rinse water as a culprit. It does ok much of the time, but for reasons I can't explain yet it can cause streaks and all kinds of weird dye problems.

An uneven oxide layer that is not evenly removed before anodizing will cause patterns and variaitons in dyed colors. Anodize layers often build up unevenly, and when it is thin you may see a pattern. Kind of like the first coat of paint on a wall with a roller, you may see light/dark patterns. By cooling the part well and thus keeping the part temerature even with good agitation you will avoid much of this.

And, due too uneven part surface temperature (if it exists in a particular case), when the anodizing time is pushed to far or other factors cause it, dissolution will likely not be even on the part, which can cause variation in the anodizing and resulting color.

I believe trying to control the anodizing process to result in some sort of artistic results in the dyed colors would be difficult to do on a predictable basis. It is probably best done by anodizing as best as possible for an even and high quality surface, and controlling the dye process either with a mask, or "acid washing", where you use acid or bleach (don't mix the two as bad things can happen) is used to lighten or remove dye. The strength of the acid or bleach, and duration left on, will determine how much color is removed. The way it is applied (i.e. crumpled cloth or paper similar to sponge painting or stenciling, or perhaps splashing), will determine the pattern. If the part is dry when acid washed, the edges will be more distinct, if it is wet the edges will be softer.

[acidrain]

MD, You mentioned something very ineteresting... the soda rinse has caused you dye problems?
Can you go into better detail on that? I swear by the soda rinse method for neutralizing the acid to avoid streaks. Maybe I'm off base on that.

[M_D]

acidrain, We have at times used both pure water to rinse, and soda water. We never had any particular problems with the pure water rinse. I first decided to implement the soda rinse because it did sound logical. Our first rinse out of the tank is to immerse in a rinse tank, and then spray rinse.

Everything seemed to be fine when first implementing the soda rinse. We had occasional problems, but were not sure what the cause was and did not make a firm connection to the soda water although it did appear to be a suspect.

At one point this summer all of a sudden one person who does much of the anodizing started to have whole racks of parts that would each have various flaws in the color, such as little streaks and spots that would be totally bare with sharp edges, and some where the spots were just lighter colored with gradient qualities. There was somewhat of a pattern to the flaws on each rack, where it would happen on one side of the rack or on the same place of each part. It was puzzling, at first I thought it was a contamination or cleaning problem prior to anodizing, but it was hard to tell if it was a anodizing problem or dye problem. Coincidently, we had just replaced a worn out cathode plate at the same time. So we were considering if it could be cathode shadowing, some type of fluke electrical situation in the anodizing tank, a faulty power supply, contaminated dye, and etc. We even looked at the metal itself having problems as we have seen problems there before. (Extruded aluminum with microscopic pores that hold acid and then and bleed acid in the dye tank, producing little bare spots). It didn’t make sense it was the metal in this case.

I told that person to change out all of the rinse tanks (we have one for each process), we made a new cleaner solution, and did run some tests in a smaller anodizing tank with different electrolyte. Nothing seemed to help, and then when discussing the problem I found that they hadn’t changed the soda rinse tank because they couldn’t imagine it being the problem. We then did a control test where we anodized a rack of parts, and then removed 1/2 of the parts and rinsed them in new pure (RO) water only, and the balance of parts were rinsed in the soda water (RO water also). The results conclusively showed the soda water to be the cause. Further incidences outline in the next paragraph confirmed soda rinse water to be a source of problems.

Then we changed it (the soda rinse) and the problem went away for a while. Then about a week or so later the problem suddenly popped up again, and we immediately exchanged the soda rinse for pure water and haven’t had a problem since then. Like I mentioned, the soda water didn’t seem to give problems all of the time previously. We do change the rinse regularly to keep the acidity from becoming too strong. On this last occurrence the problem stopped our anodizing production for a week or more before solving it.

I am not comfortable in saying that neutralizing the acid with soda water is to be completely avoided, and for people to abandon the practice if nothing is wrong in their results, but we did see where there are potential problems at least under certain circumstances. I can’t explain what exactly was happening, and maybe it is something rare that requires certain circumstances. I do know that the time the parts sat in the soda rinse had an effect on the intensity of the problem (say 10 seconds compared to 2 minutes). We also use Ti racks, and perhaps there is some sort of reaction there, as there is with 2000 series aluminum and Ti racks. At this time, it is not a problem anymore, and so I haven’t devoted further time into finding the explanation. I don’t know if commercial anodizers commonly use a soda rinse or not.

By sharing this information though, it may help others to solve their problem sooner should it occur.

[Sid03]

I once had a strange issue that nobody could figure out. Do you happen to have pics of what the failed parts looked like?

Also, what reaction do you see with Ti racking and 2000series alloy? I havnt noticed anything when I run 2000series.

[M_D]

Sid, I don't have any pictures of the parts. I do still have pictures you sent of parts that may be some of the ones you are talking about. I looked at them and there are some similarities, but I can't say if it was the same thing or not.

The 2000 series aluminum will set up some sort of galvenic or similar reaction. The longer they are left in the dye the worse they get. They get little spots that grow something on the surface, and I have seen where the spots are either lighter or darker in color. It happens only with Ti racking in my experience, and a commercial shop owner told me that's what their experience was too. When the parts are anodized on Ti racks and then taken off the Ti rack to dye they seem to come out ok. We ran a bunch of control tests, and 100% of the time it worked out the same, the parts hanging on individual wires could be dyed even overnight with no ill effects. The parts on Ti racks got ugly every time if left in the dye long enough to dye to close to saturation, perhaps over 15-20 minutes, I don't remember for sure now.

We have got some pretty nice looking 2011 parts, but prefer not to use it because the anodizing is just not as easy and nice as the 6000 series. It's too bad, because the 2000 series machines nice in lathes because the chips break up so well, instead of forming long stringy shavings that tend to wrap around the part and tools.