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View Full Version : First attempt at anodized aluminum



gtcway
05-22-2006, 02:27 PM
I've had a Thermal Arc 185 tig for a couple months now. I haven't don't much lately but decided to try some anodized aluminum pipe, the stuff that's used to make t-tops for boats.
I noticed that welders who don't work on t-tops recommend removing the anodizing at the weld joint and welder who do weld without removing it. I've also noticed that most welds look like mine with the little black bits mixed through the bead. Is this acceptable or can I improve it? The welds are a little rough as I was concentrating on getting a clean bead.

http://www.greatabaco.net/temp/weld01.jpg

http://www.greatabaco.net/temp/weld02.jpg

I used 50% on the balance for a little more cleaning action, any more and I keep balling the tungsten. If I increase the cleaning and weld with a balled tungsten will it hurt the welder? I thought I saw somewhere that using a balled tungsten on an inverter can cause it to work too hard, maybe? The pipe is 1" OD

If you look at the picture at the bottom of this page on Miller's site they claim there was no polishing or cleanup after the weld.
http://www.millerwelds.com/education/articles/story93.html

JMO
05-23-2006, 12:54 AM
welding anodized aluminum is VERY dangerous. ...poison......

gtcway
05-23-2006, 08:38 AM
I could be wrong but I believe you're thinking of galvanized steel?

smithboy
05-23-2006, 10:07 AM
I have never heard of anodized coatings being any more or less poisionous than the base aluminum...That's something to check.

However, the reason you are getting that speckled, grainy look is that you are getting contaminated welds. The main reason for removing the coating is to make welding easier and sound. Good looking, good quality aluminum welds need to start with very clean metal. Most of these coatings can be removed either with an abrasive or with a chemical etching solution. Some here have suggested muratic acid as a reasonably safe etching solution for aluminum. (Other acids are used also, but some are very unsafe, especially for folks not familiar with their hazards). I don't know what concentration of muratic acid to recommend, but others here might. By the looks of the tubing, you might be able to use a stainless wire wheel and do a pretty good job removing the coating in a short period of time. I would start there before progressing to chemicals. Once the coating is removed, welding will be easier and the welds' appearence will substantially improve.

gnm109
05-23-2006, 10:40 AM
I've had a Thermal Arc 185 tig for a couple months now. I haven't don't much lately but decided to try some anodized aluminum pipe, the stuff that's used to make t-tops for boats.
I noticed that welders who don't work on t-tops recommend removing the anodizing at the weld joint and welder who do weld without removing it. I've also noticed that most welds look like mine with the little black bits mixed through the bead. Is this acceptable or can I improve it? The welds are a little rough as I was concentrating on getting a clean bead.

http://www.greatabaco.net/temp/weld01.jpg

http://www.greatabaco.net/temp/weld02.jpg

I used 50% on the balance for a little more cleaning action, any more and I keep balling the tungsten. If I increase the cleaning and weld with a balled tungsten will it hurt the welder? I thought I saw somewhere that using a balled tungsten on an inverter can cause it to work too hard, maybe? The pipe is 1" OD

If you look at the picture at the bottom of this page on Miller's site they claim there was no polishing or cleanup after the weld.
http://www.millerwelds.com/education/articles/story93.html


Other than the obvious contamination, your welding technique is fine. BTW, as far as I know, welding alumimum is not inherently dangerous assuming proper ventilation and good safety practices.

I don't know whether a balled tungsten is hard on an inverter unit but I was always taught in welding classes that a balled tungsten (pure) was ideal for welding aluminum. I have since learned using my own machine, a Lincoln Idealarc 250/250 DC/TIG, that when welding with AC, even when you start with a sharp pointed tungsten, a ball will form. This is due to the alternating current varying between + and - when compared to zero. Unlkke your machine I don't have any way of balancing between cleaning and penetration. I'm always at 50% so I don't worry about it.

Anodized coatings are much harder to melt than the underlying metal. Thereore, if not removed, it causes trouble by forcing higher temperatures to burn it off, at which point, the underlying metal may melt away before you get a chance to back off.

A little more time spent cleaning and prepping before welding will remove most of the black impurities you see. I use a stainless brush that's only used on aluminum as well as a cleaning solution that I get from the local Airgas. It really helps a lot.

Otherwise, the work looks good. :)

smithboy
05-23-2006, 10:53 AM
Follow up:
I don't think you are supposed to use pure tungsten on an inverter. You don't mention which tungsten you are using, but it sounds like you might be using pure. The other mixes are not as prone to balling.

It looks like on the miller site these folks are using a techinque that possibly employs the hot start to spread the coating (using added cleaning maybe), they then add filler, and then allow the coating to re-cover the area somehow. Sounds a bit tricky, but not too complicated an idea. I would be concerned that without starting at a bare spot on the surface, you would melt the metal before you could add filler, though. Notice that they do not provide the step-by-steps...my guess is that they want to tout the capabilities of the machine without giving away too much about the methods.

Bright aluminum that's anodized will weld easier and better if the coating is removed, and it will not substantially affect the looks after it's welded. I don't know if the contamination you are getting will substantially affect its performance, but I imagine it could be an issue if winds are pretty strong.

You might send the miller folks an email and ask for a more detailed expo on that method...sounds pretty interesting.

gnm109
05-23-2006, 11:34 AM
Follow up:
I don't think you are supposed to use pure tungsten on an inverter. You don't mention which tungsten you are using, but it sounds like you might be using pure. The other mixes are not as prone to balling.

It looks like on the miller site these folks are using a techinque that possibly employs the hot start to spread the coating (using added cleaning maybe), they then add filler, and then allow the coating to re-cover the area somehow. Sounds a bit tricky, but not too complicated an idea. I would be concerned that without starting at a bare spot on the surface, you would melt the metal before you could add filler, though. Notice that they do not provide the step-by-steps...my guess is that they want to tout the capabilities of the machine without giving away too much about the methods.

Bright aluminum that's anodized will weld easier and better if the coating is removed, and it will not substantially affect the looks after it's welded. I don't know if the contamination you are getting will substantially affect its performance, but I imagine it could be an issue if winds are pretty strong.

You might send the miller folks an email and ask for a more detailed expo on that method...sounds pretty interesting.

===================
You've aroused my curiosity now. I wonder if you could explain the issue regarding pure versus mixed percentage tungsten used with an interver. What would the negative effects be? Why is the interter more vulnerable to changes in Tungsten types? I've heard that you shouldn't use pure Tungsten with an inverter but never heard why.

I've always used pure Tungsten on aluminum but admittedly, my machine works from a transformer and not an inverter. Also I don't recall what sort of machines we had at school since it was some ten years ago. I think most of them were pretty old but they worked well anyway. I do know that we always used pure Tungsten on aluminum at the school.

So I used to think that that pure Tungsten was the tool of choice for aluminum but lately, I've heard that 2% lancinated might be better. Any idea why? I may want to change my electrodes.

Thanks in advance.

:)

gtcway
05-23-2006, 12:45 PM
The reason I trying to figure this out is it seems that people who weld t-tops don't remove the coating, and some paint the weld with silver paint to make it look better. I'm going to try this afternoon with more amps and faster, I've been slowly adding heat on those welds. Also, I going to increase the hot start amps, I was running 30, but can go up to 70 amps.

On the tungsten, I used langthernated (possible spelled wrong) and I also have thoriated. I've heard that you don't use pure tungsten on inverters because they have a lower melting point. You don't want a ball with an inverter, but do on a transformer IIRC.

smithboy
05-23-2006, 01:31 PM
The Miller tig guide recommends against pure tungsten on its inverter machines or in any DC application. Truthfully, I am not sure why not (for the inverter), but I have heard several reasons, none of which do I fully accept. Here is one vague explaination from a miller rep on thefabricator.com that I might believe if it were better explained. See the bottom of the article.

http://www.thefabricator.com/Consumables/Consumables_Article.cfm?ID=834

"If you’re welding aluminum or magnesium with an AC inverter and use the wrong tungsten, you won’t get the maximum benefits from the advanced square wave technology."

I suspect they are talking about pure with an inverter here...but, I am not 100% sure.

I use a transformer-based tig machine also, but have a dc inverter for some tig applications. With the transformer machine, I've use both pure and lanthanated with only a bit of difference between the two in the weld appearence...I used lanthanated the first time with aluminum because I misplaced my pure tungstens. I got ok results for what I was doing even without balling the tungsten (which isn't as easy as on pure tungsten, by the way)...now I use lanthanated occasionally on aluminum because I am too lazy to switch between the two when it doesn't seem to make a huge difference and/or what I am doing isn't that critical. I also have used the same tip shape on aluminum as with steel...the bead is raised and narrower, but that's about it. If I am doing something important, I switch to pure, but for little stuff or non-critical stuff, I just use what ever I used last time, pure or lanthanated.

Since you (gnm109) are using a transformer machine, I would say pure is still the tool of choice, but variety is the spice of life...grab a lanthanated and giver' a whirl.

pulser
05-23-2006, 02:29 PM
Diamond Ground Products has a good explanation of the effects of the various oxides of thorium, lanthanum, cerium, and zirconium that are added to tungsten welding electrodes.

http://www.diamondground.com/Guidebook0105.pdf

Tell me, is there any real reason that the type of tungsten being used would affect the power supply? I don't think so. This doesn't make any sense. After all, you can use a modern inverter power supply for TIG or SMAW, the power supply doesn't care if the electrode is pure Tungsten, 2% Thoriated, or E6011.

Back in the day, pure tungsten was recommended for AC TIG of aluminum because it balls up easily at lower current and doesn't tend to get a crater or split in the ball like 2% thoriated.

The reason you choose one type, size, and end preparation of a tungsten is to get good arc starting, good arc stability, and good electrode life. Under moderate welding conditions, the weld appearance should not be affected by the tungsten choice. The thing that matters to the weld is arc density and stablility. Any type of tungsten can become erroded or contaminated and result in an unstable, diffuse arc, and an irregular weld.

smithboy
05-23-2006, 03:00 PM
I personally can't see why one type of tungsten electrode would affect the supply any different than another...however, there are several threads on several boards that warn of vaguely horrible results for the machine...you know..."It will void your warranty, or burn it up, or make it lose its memory, wet itself, and wander aimlessly through the neighborhood cursing strangers." I really am not sure, but I am also not sure if I would be willing to spend $2-3k on a nice inverter and then roll the dice. I really doubt that any manufacturer can tell what kind of tungsten you used anyway. I have seen the inside of some of these welders and they dont seem to have anything that looks like a tungsten alloy recognition system (TARS), so, how could they tell???

By the way...as always, if anyone KNOWS pure tungsten WILL or MAY damage an inverter welder, I will be glad to reconsider my position (or lack thereof) with a good explaination of how/why it happens.

prop-doctor
05-23-2006, 06:13 PM
YEP spice of life i use 2% tungsten, have for 16 yrs no probs but it works for me, but all i do is alumin-and -stainless (pure argon 12-15cfh)

prop-doctor
05-23-2006, 06:13 PM
oh same machine idealacr250

rcweldr
05-25-2006, 10:18 PM
It sounds like you are allowing too much heat to effect the weld. When you are welding anodized it is a different art all together. I used to build the towers on boats that you are talking about, and I had the same problems at first, until another welder came to me and showed me that pulsing the arc one drop at a time makes the weld come out as if you were welding 5356 or 4043, or even 6061. We also would hand paint the welds sometimes when a "pretty weld" was unattainable.

I have used both pure tungsten and 2% thoriated and I personally had better results with the 2% because when thorium is added with the tungsten, it does not burn up as fast, or ball up for that matter. You can also use a pointed tungsten for when you are welding thin gauge material because when the tungsten balls up it will be much smaller, therefore effecting less area on the workpeice. I hope this helps answer your questions. Let me know.