distilled vs. tap water and anodize time too short

[blackcote]

Anyone know what the effects of using tap water are in anodizing
Does it increase needed anodizing time?

Only thing I've found by searching is blotchiness. Which I'd be ecstatic if I could get it that good. My problem is that it seems that the 720 rule is useless for me as my setup seems to want to run twice the amount of time to get a good deep color. I did many experiments to no success. I've wasted a ton of time trying to use current densities and 720 rules. None of it is getting close for me. The only other two variables that I haven't nailed down yet were the acid ratio of electrolyte. and whether I have a good enough connection (resistance)

I've made a new batch of acid to start with tomorrow night. This may be my last attempt before giving up. We've done it before using a battery charger and tap water. We can't remember how long we left the part in the solution. I thought CC would help me get more consistent, which I believe it has but the shade is defintely not dark enough. I've had my customers parts for like 3 weeks and don't even know if I feel up to charging him after taking so long.

[neilfj]

Tap water can cause all sorts of problems, depending on its chemical makeup . Blotches are the typical results. High concentrations of iron, copper and other metals can have the effect of destroying your electrolyte and I imagine that chlorine would have cause negative effects too.

Can it cause changes in the amount of time required to anodize...definately, if it will anodize at all. I can't give a much more precise response since everyones tap-water is not only different, but tap water can change chemically from day-to-day.

[Fibergeek]

That depends on the tap water, if yours is "hard" it contains significant mineral contact. The presence of iron is bad, copper even worse.

Where I am (Maryland) the tap water is pretty soft; still, I use only distilled water (grocery store) to make up electrolyte and dye solutions. I use tap water for rinsing with no ill effects.

I'm assuming that you found an appropriate thermometer, and are now anodizing in a 70 -75 deg. F. range.

I'm not real clear on the actual electrolyte concentration you are going to use; if your going to operate in the 3 to 6 A/sq.ft. range LCD) you should be using 1:3 battery acid to water. Above 6 to about 15 A/sq.ft. use 1:2 battery acid to water.

BTW, personally I like 6 A/sq.ft. the best for LCD.

The 720 Rule is quite reliable, something else is going on. The wrong acid ratio for the current density will make trouble, degrading connections can easily cause failures and usually does.

You may not have COMPLETELY removed the natural oxide from the work, doing this chemically isn't as easy as it sounds. Thoroughly sanding a test sample to be sure the oxide is removed would be a good test to see if this is going on.

[Fibergeek]

Good point about chlorine Neilfj.

Chlorine in the electrolyte definitely degrades the electrolyte.

I'm in Chicago, this hotel has DSL connections in the rooms.

[M_D]

Successful anodizing really depends on just a few basic factors, such as parts that have a clean surface and are free of oxide, a good electrolyte, and getting the right amount of current for the right time. But, the devil is in the details and it isn’t always as easy as it sounds.

We know that the electrolyte is critical, but yet there is some latitude for mix ratio, although certain contaminants are bad news.

The time and current can actually be varied quite a bit, and still have nice looking parts. A shorter anodize time will result in slower dying and/or a final lighter color. It should still be even though. Anodizing for longer periods can help speed dying and result in deeper colors, although that only goes so far and then there is no benefit to appearance.

You do need to be sure the connections are good, I would recommend doing a few test parts where the part connection is out of the acid. Try to make the connections as good as possible. If that doesn’t fix the problem then something else is the cause.

I don’t know what kind of parts you are doing, so it would be hard for me to recommend any specific cleaning cycles. What you need to end up with is a fully clean part, with as little oxide as possible. Sanding a test area would be a good step. If you find it works better, then you may need to use a more aggressive de-oxidizing step in the cleaning cycle. Oxide will cause unevenness and light depths of colors. I have found our machined parts anodize nicely without de-oxidizing at all. We can scrub them with bristle brush and dish soap until the water sheets, and that gives as good of results as anything. We don’t do them like that now because it is impractical except for limited volume.

When the same parts are tumbled to de-burr and even the surface that completely changes things. Then they need to be cleaned much more aggressively. We are using the SP cleaner, and have found when heated to 200º is cleans faster and more completely. For parts with very low mass that will heat up almost instantly, it will do a fair job of de-oxidizing. It will not satisfactorily de-oxidize larger parts, because their mass doesn’t allow them to reach the high temperature fast enough. Those parts require a lye etch or equivalent. A general rule I have found that works is this: if the parts develop a light coating of smut in the lye etch, they are probably de-oxidized well enough. If the lye is mixed too weak and it is cold (room temp), it can take forever to work. We use a strong enough solution and heat it to 140º or so, and it takes 1-3 minutes to get the smut layer that says it is de-oxidized. The lye will work faster when heated, but if it is heated too hot it can get weird, 120- 140º is more than sufficient.

The smut needs to be cleaned, Caswell’s de-smut works well for this. It also works faster when heated, but it isn’t required. When the smut from the etch process is gone, and the parts have a bright look they should anodize to a nice finish.

I am assuming you don’t handle the parts once the cleaning is started, and rinse real well between steps.

I’m curious, what color are you dying the parts? Also, what alloy is the aluminum and what kind of surface?

If you try some tests and can’t get it to come around, you might suspect the CD is out of line; maybe the meter you use is wrong. Also, if using distilled water to mix the electrolyte doesn't solve the problem, I think it is a good possibility the parts need to be cleaned better, whether just degreased and/or de-oxidized better I couldn't say with the information I have.

[blackcote]

Before I get started.... what does high sulfur content in tap water do to the acid solution?

So I gave distilled water a try last night. No luck same results. Here's how I went about things. I've been pondering on this process for some 2 weeks now and decided that I was sure it wasn't being anodized long enough (what is causing it is anyones guess or investigation). So I decided I was going to try something.

dip part in ano stripper for a minute or two.
rinse w/ tap water
dip part in de-ox de smut for a few seconds
rinse w/ tap water
anodize part (.06 SF) in 1:2 acid to tap water for 45 min at 30A/SF (I was guessing that it needed to be anodized twice as long but didn't want to wait that long) Part came out looking similar to what it should (not silver or light grey)
rins w/ tap water
soak in dye for 20 min at 140F
hmmmm looks better but still not good nice dark grey color
now here's the kicker.
I stuck it back in the anodize at 60A/SF for 15 min
went through the same process and got a beautiful jet black color
sealed it for 15 min... minimal dye came off the part and it stayed black
wohooo one good part in 2 weeks... too bad it was a sample.

next test....
sample piece w/ .03125 SF of SA.
go through the same prep steps
put in 1:2 ratio acid to "DISTILLED WATER" at 15 ASF (.5 amps) for 45 min temp right around 70
hmmm this don't look good... still silver... what the heck am I doing wrong... voltage never dropped or wet up drastically like a lost connection... voltage slowly rose was around 16ish and rose to 18 ish
so I rinsed it and dyed it anyway for 40 min and it was light grey.

i give up at this point and decide to do some other parts. mat'l was unknown. I was told either 6000 series or 7000 series... gee thanks for the help on that one. So I put 4 pieces in totalling .66SF set amps at 11 for a little fudge factor over 15ASF since I'm getting crappy results anyway. Consistent... but crappy. Well it started at 73ish degrees... till I got to my 45 min It was at 85 degrees Didn't even cross my mind about heating the solution too fast. They were med to dark grey coming out of the acid. i rinsed and died anyway and they were then dark grey and the dye really didn't take all that well. Is this what typically happens when you get past the 78 deg mark?

for additional information on my original acid make up I stuck a part in it and hooked up a battery charger to it and it worked out to 28 ASF to start with and then in a new known 1:2 tap water solution and it worked out to 15ASF. Just thought it was something I found that was interesting. Don't know if it means anything though

My next attempt will involve getting multiple small pieces and start removing them every couple minutes and placing them in the dye to see how long I really have to anodize for. I also read something about anodizing with the connection out of the solution to rule out a bad connection. I might try that too. Only thing I can figure is I have really bad tap water and have to buy new sealer, dye, deox, and stripper. Sometimes I hate being stubborn and keep at a challenge till I get it.

[neilfj]

Edited parts of the 720 Rule Formula which I originally posted incorrectly

Originally Posted by blackcote

Before I get started.... what does high sulfur content in tap water do to the acid solution?

I don't know specifically what chemical reaction may take place. It could range from nothing to creating sulphur dioxide (rotten eggs). Generally speaking, any contaminate in the electrolyte can interfere with the conductivity of the solution, interfere with the chemical reaction, or both.
The reason distilled water is specified is to eliminate the potential of any contaminate causing problems. This is also true with the stripper, de-ox/de-smut, sealer and dye. It is difficult to control reactions when unknown elements are added to the mix. The reaction of the chemicals in the tap water can cause spotting, discoloration, brittleness of the surface, incorporation of other chemicals into the structure of the anodized cells, and generally all kinds of issues. Your specific problem may not be due to the use of tap water, but as a general practice its use should be discontinued.

dip part in ano stripper for a minute or two.
rinse w/ tap water
dip part in de-ox de smut for a few seconds
rinse w/ tap water
anodize part (.06 SF) in 1:2 acid to tap water for 45 min at 30A/SF (I was guessing that it needed to be anodized twice as long but didn't want to wait that long) Part came out looking similar to what it should (not silver or light grey)
rins w/ tap water
soak in dye for 20 min at 140F
hmmmm looks better but still not good nice dark grey color
now here's the kicker.
I stuck it back in the anodize at 60A/SF for 15 min
went through the same process and got a beautiful jet black color
sealed it for 15 min... minimal dye came off the part and it stayed black
wohooo one good part in 2 weeks... too bad it was a sample.

How are you making the connection? At .06 SF, I suspect you may have a connection problem. Being such a small piece makes it difficult to get a good connection.

i give up at this point and decide to do some other parts. mat'l was unknown. I was told either 6000 series or 7000 series... gee thanks for the help on that one. So I put 4 pieces in totalling .66SF set amps at 11 for a little fudge factor over 15ASF since I'm getting crappy results anyway. Consistent... but crappy. Well it started at 73ish degrees... till I got to my 45 min It was at 85 degrees Didn't even cross my mind about heating the solution too fast. They were med to dark grey coming out of the acid. i rinsed and died anyway and they were then dark grey and the dye really didn't take all that well. Is this what typically happens when you get past the 78 deg mark?

Yes. The higher temp increases the speed at which the anodizing layer is eaten away by the acid. The acid eats away at the cell structure of the layer until the cell is so large, it won't hold the dye well.

Before you spend any more money, would you be will to send me a sample or two of what you are attempting to anodize? I doesn't have to be a machined piece, just a piece the approx. size and of the same material you are attempting to anodize. I just finished an anodizing test yesterday and I'm still set up. I'd be willing to give it a shot and let you know what works. I should be able to turn it around in a couple days. Let me know if this will work for you and I'll send you my address.

Sometimes I hate being stubborn and keep at a challenge till I get it.

I know exactly what you mean...Ask Fibergeek about how stubborn I am!

Anodizing at 30-60amp/sq ft? WOW! {edited}[b]We're use to lower currents, but some of the basic rules should still apply. At 30 amps the sample should be in the electrolyte for {edited} 24 minutes based on the 720 rule for a 1 mil thickness. Having it in for 45 minutes may be too long and it may be opening the pore structure so that the dye doesn't absorb. At 60 amp density, it should be in for 12 minutes. Your 15 minutes probably didn't make much of a difference..

Edited to add:

I'm currently set up for the LCD method. I can run the test and get the samples back to you so you can see how well it works. As Ford said, any color can be ordered, as long as it is black (since I only have the black dye).

[mcaswell]

Sounds to me like you need to throw out whatever instructions and solutions you have currently used, and start over using the complete LCD instructions and following it to the letter.

Why wing it and experiment with this when LCD is a proven system?

[blackcote]

Well before we go to either of those extents... I will try to start fresh with the a new piece clean it by hand. Maybe a good time to mix up my degreaser/cleaner. rinse with distilled and try again. keeping all tap out of the mix

Sounds to me like you need to throw out whatever instructions

What's wrong with my instructions? The general process follows everyones method that I've seen. Difference is in the higher current density and I WAS using tap water. Am I doing something wrong that you see? LCD is not an acceptable method for us solely on the time factor. I just don't have that kind of time.... although you could argue that I do since I've been spending so much time trying.

Anyway to the more helpful answers. Connection is made via a 0-40A 0-40V power supply. From that through a 2 conductor wire with spade terminal clamped to the cathode and anode (.5" sq bar with holes drilled through... then Al thumb screws in the bar which hold the Al wire in the bar. the wire is threaded using pliers into a threaded hole on the part.) the cathode is made of an 8" dia lead plate w/ an Al bar attached while the lead was still hot and molded around it. comes up out of my tank and bent 90 deg to attach lead from power supply. You thinkin maybe my power supply is lying to me

Alloy I'm not positive but believed to be 6000 series except for that last batch. I have some known 6000 parts but those are ones I don't want to ruin before I get some success out of this. I think I will get some new pieces of 6000 made. and keep the tap water off it. Keep that spot open though. I may take you up on it. If I can't get this to work or the LCD mix.

[neilfj]

Disregard the calculations regarding the 720 Rule. They are incorrect. See bottom of thread

Justin;

The problem is, as far as Caswell is concerned, that they only support the LCD method. I've tried the battery charger and the high current methods and have had no success. The LCD method has worked repeatedly for me, but I understand your issue regarding time.

Since time is a factor, and you already have a batch of 2:1 electrolyte mixed, try it at an 18 amp current density.

Just so all the math matches:
For a piece 0.06 sq/ft, your setting on the power supply would be about 1.08 amps (a little variation isn't going to have much of an impact). Make sure it is in CC mode!!!

According to the 720 rule, you should anodize for 2.5 minutes.
(720 / 18 amps * 0.06 sq ft * 1 mil) I picked 1 mil as your desired coating thickness)

As you state, keep the tap water out of the mix. It may turn out to be a non-issue depending on the quality of your tap water, but at this point, lets eliminate as many variables and potential problems as possible.

Sorry about the repeated question about the alloy. I missed your statement about it being either 6xxx or 7xxx.

Is your electrolyte being agitated? If you don't have a pump set up for this, use a wooded spoon or plastic spatula to stir the electrolyte for the 2.5 minutes you are anodizing. The agitation does make a dramitic difference in the results.

Actually, the connections that are of major concern and the cause of most problems are:

1. The connection to the cathode plate. is the attachment point between the lead and the alum. air tight? It is possible that if electrolyte leaked into this area, it would ruin your connection. If possible, pull the top of the cathodes out of the electrolyte. This will eliminate the potential of electrolyte getting into the connection. If the connection point has already leaked, you'll have to clean it. Aluminum and Lead salts have a tendency to build up at this connection point and can ruin the connection.

2. The threaded connection to the anode. Are you tightening the connection, almost to the point of the aluminum breaking off? You have to tighten it so firmly that the metal from the alumimum wire 'cold forms' and flows into the threads of the anode. Otherwise, electrolyte will get into it and the connection point will anodize and not the part itself.