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Thread: Anodizing Defect Identification

  1. #1
    Countryboy1966 is offline Amateur Metal Finisher
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    Default Anodizing Defect Identification

    I just determined it may be a loose connection I just found, but if you are interested in looking at a problem to confirm, please feel free to read on. I'm interested in sharing my experience for all to learn from.

    I need some help identifying a defect that happened on my last run. Pictures are below.

    Degrease 140°F @ 12 minutes (Passed water break test)
    Desmut 110°F @ 10 minutes
    Anodized at 5.0 ASF @ 100 minutes 68°F

    Parts were pulled from anodizingicon bath and looked really good. No visible signs of this defect. I would not have detected if I was clear coating.

    Within 5 minutes of being in the bath, dark spots appeared. Dyed for 20 minutes at 100°F

    Proceeded to seal 20 minutes at 200°F

    Marks were still there.

    http://i243.photobucket.com/albums/f...6/100_6345.jpg

    http://i243.photobucket.com/albums/f...6/100_6346.jpg

    http://i243.photobucket.com/albums/f...6/100_6349.jpg

    Continuity was good before at 0.00 resistance on the racking systemicon alone. Many sucessful runs since I straightened out my bath. I thought this was behind me.

    Another issue I have been observing is a decrease in V required to hit the required Amps.
    For instance, what took 13 V to hit 5 amp is now taking 11.5V. It dropped progressively over the last two-three runs. This confuses me, but I am reading that if it is dissolved aluminum it isn't too big of a deal? I'm wondering how many runs I can make until dissolved aluminum is an issue. I anodizeicon approx. 144 in square per run.

    I did notice I have had some evaporation maybe three quarts of water.

    I also did another project where a small ammount (less than 1 cup) of well water got into my air line that I use for agitation. I have heavy iron content, but I rinsed and dried my line out. I have a separator on my compressor so residual would not carry.

    One picture shows the condition around my racking marks to it leads me to think I may have a connection issue, but could the connection issue be in the cathode/annodes? I have copper clamps that have corroded, but the .....

    As I read this I realized I never checked the connections for continuity. Everything seemed good at zero resistance, but then on the last clamp there it was a very loose connection. I'll re-run and let everyone know what I find.

  2. #2
    ddrink is offline Amateur Metal Finisher
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    Default Re: Anodizing Defect Identification

    Quote Originally Posted by Countryboy1966 View Post
    Another issue I have been observing is a decrease in V required to hit the required Amps.
    For instance, what took 13 V to hit 5 amp is now taking 11.5V. It dropped progressively over the last two-three runs. This confuses me, but I am reading that if it is dissolved aluminum it isn't too big of a deal? I'm wondering how many runs I can make until dissolved aluminum is an issue. I anodizeicon approx. 144 in square per run.

    I did notice I have had some evaporation maybe three quarts of water.
    I think you solved this issue too. Losing water increases the acid concentration, which requires less voltage.

  3. #3
    Countryboy1966 is offline Amateur Metal Finisher
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    Default Re: Anodizing Defect Identification

    Thanks DDrink.

    I'll know the effectiveness of the process changes this weekend. I'll let you know what I find.

  4. #4
    spankey666's Avatar
    spankey666 is offline Metal Finishing Guru
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    Default Re: Anodizing Defect Identification

    check your dyeicon ph and filter your dye. i did some experimenting a while back and deliberatly contaminated some dye with acid. small clumps formed and created spots with meteor tails just like your picture . also check the surface of your electrolyte for contamination from oil, small droplets will transfer to your part when you remove them from the tank causing similar looking spots. (notice the spots have tails trailing in the same direction )
    "A stupid man's report of what a clever man says is never accurate because he unconsciously translates what he hears into something he can understand.
    Custom Anodising

  5. #5
    Countryboy1966 is offline Amateur Metal Finisher
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    Default Re: Anodizing Defect Identification

    Just following up. Its been a while. I found the following problems:

    1.) Loose connections on clamps.

    2.) Incorrect ratio due to evaporation

    3.) The thermometer I use to take acid bath temps was broken where the probe and indicator could spin freely in relationship to temperature markings. I think my temps were way to high causing havoc.

    Corrected all three and I am back in business.

    I am also going to look into the other suggestions as process improvement opportunities.

    Thanks!

  6. #6
    Countryboy1966 is offline Amateur Metal Finisher
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    Default Re: Anodizing Defect Identification

    Well everything went back to normal except on the second run in a different dyeicon color I ened up with clear spots where dye didn't take.

    Filtered dye with a Paint strainer and problem went away. Found a sludge substance in the dye.

    I am going to get more filters and strain again to be safe. Thank you for the tips guys!

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