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Thread: Anyone anodizing in shop? Experience with sealant bloom?

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    Anyone anodizing in shop? Experience with sealant bloom?

    I've recently started anodizing parts in shop (in very small volume atm) with a decent level of success. I am, however, having the occasional problem. The last batch I made ran into some cosmetic issues after sealing in a nickel acetate solution. After I took the parts out, I observed a white powdery build up on about half of my parts. After I brushed it off, the parts were discolored as can be seen in this photo. -photo-1-jpg

    I know that this is sealant bloom and have been able to buff out the markings. Still, I'd like to dial in my process so that I don't need to do any hand finishing after anodizing. I've read that soaking the parts in nitric acid will remove the bloom; does anyone have experience with this?

    Does anyone have any recommendation for simply preventing bloom while sealing?

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    Quote Originally Posted by FuriousGeorge View Post
    I've recently started anodizing parts in shop (in very small volume atm) with a decent level of success. I am, however, having the occasional problem. The last batch I made ran into some cosmetic issues after sealing in a nickel acetate solution. After I took the parts out, I observed a white powdery build up on about half of my parts. After I brushed it off, the parts were discolored as can be seen in this photo. -photo-1-jpg

    I know that this is sealant bloom and have been able to buff out the markings. Still, I'd like to dial in my process so that I don't need to do any hand finishing after anodizing. I've read that soaking the parts in nitric acid will remove the bloom; does anyone have experience with this?

    Does anyone have any recommendation for simply preventing bloom while sealing?
    I've gotten the same results after sealing using a nickel acetate sealer. I let the parts 'cure' for 24 hours and then buff them using a anodizing friendly polish (not all polishes can be used on anodized aluminum, check the bottle for allowable surfaces). This has worked well for me. I don't always get the white markings but they seem to occur more often as the sealer solution ages which implies a potential cross contamination issue from not rinsing enough coming out of the dye tanks.



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    Thanks! I think we're dealing with the exact same situation. My nickel acetate sealer was getting pretty old (~60-80 days), and this is the first time it happened. I also think there is a good possibility my water bath was contaminated with some tap water, so that could have added to it as well.



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    Registered BAMCNC.COM's Avatar
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    I only anodize Titanium, but have all the stuff to do Aluminum. So are we thinking its cross contamination, or old sealer? If old sealer, is it just perhaps to concentrated now due to evaporation?



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    I think cross contamination is the most likely candidate. I gave the parts a spray rinse rather than a good dunk in distilled water after the dye. I also had washed out my neutralizer tank with tap water rather than distilled, so it could have gotten some particles on it from that as well, although I think the dye is the primary reason.

    I had marked the waterline in the sealant tank when I first mixed it and the change was negligible, so I can totally rule out evaporation as a culprit.

    Another reason I think that it is cross contamination due to poor rinsing is because only SOME parts in the same batch had the discoloration. If the entire batch of sealant was bad, I would expect to see a little discoloration on all my parts instead of a handful.



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    It really sucks when everything goes awesome for months and all of a sudden... splat ! I've seen a ton of issues from the famous little white innies & outies dots, discolor areas, dark spots, foggy finish, etc.. It's really trial and error ! It will only make you better as you continue.

    I've ran seal 6 months to a year, zero issues. Low temp MTL seal usually only goes bad after repeated heating & cross contamination. CC will kill any tank period and should be avoided. Might be easier to run us through your steps, temps, chemicals used, etc..

    Have you alcohol tested both areas of the part ?

    Last edited by twocik; 07-21-2013 at 03:40 AM.


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    I really like having the ability to anodize now, it adds a lot of options for my projects. Even with the occasional quirks and unexpected results its well worth the time, money and effort to set up the line. I only have a small setup but have 8 colors available but have only used black, gold and red so far. I've done a little bit of multi-color anodizing, that process can be very tricky!

    Best of luck to anyone trying this on their own and be prepared for errors. My first few batches had close to a 95% rejection rate but after a couple of weeks I was down to a more manageable <5% rejection rate.even there I was able to 'hide' flawed pieces most of the time and not strip them back down.

    Bob



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    I've never heard of alcohol testing, care to elaborate? Also, do you have any advice for determining how long to seal the parts? I think I may be sealing too hot for too long. My process is as follows:

    I start off de-greasing the parts in SP degreaser from Caswell for 5 minutes at around 150 F. After degreasing I rinse the parts in Distilled water (DW) and go straight to anodizing. I skip the de-smutting process because I don't use any acids to clean my parts (which are 6061) and I've observed through trial and error that it really doesn't make a difference on my satin black finish. Parts are then anodized at 15 V and 0.04 Amps/ in^2. I went for 105 minutes in this batch. I'm still experimenting with times and tend to think I'm running it for a little bit too long for the black finish I'm after. I keep that acid-bath at 72 F for this process and agitate the tank with compressed air. I then dunk my parts in a mixture of baking soda and DW to neutralize any acid, give them a quick spray rinse with DW. I then drop the parts in a black dye tank heated to just under 140 F. I don't add any additional heat to the tank and I let the parts sit for around 15 minutes moving them around occasionally; the dye cools off by about 15 degrees throughout. After this, I spray the parts with DW and put them in a nickel acetate sealer. I realize now that I should have done a full dunk in DW, but hindsight 20/20 I guess.

    I'll have the nickel acetate at a good boil before I put the parts in. I measured it at 210 F. I close the lid on the bucket, leave the parts in and let them sit for 30 minutes with two heaters in the tank. Basically, I get the sealer as hot as I can with two 750 Watt heaters. I think this temperature and time may be too extreme, but it's still all trial and error for me. After sealing, parts get a final rinse in DW, dried and coated with WD-40.

    I'm very new at anodizing, but I find it a thrilling process. I do mostly R&D and relatively small production runs, so the ability to anodize myself is a total game changer. Haven't jumped into multi-color anodizing yet, but that's definitely an ambition once I get the basics more dialed in.



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    Hi George,
    I learned the alcohol test from anodizing guru Robert Probert, very intelligent individual !! Using 91% rubbering alcohol, wipe a colored ano surface to check if the part was sealed properly. If the color comes off on a terry cloth, you need to look into your last step. Alkaline etch basically removes unwanted oxide and desmut takes the smut off after the etch tank. 6061 you can skip these steps as long as your part was properly cleaned. If your parts are polished before the cleaner, you outcome should be polished skipping the etch & desmut tanks. If not you need to monitor your tanks temp, agitation, rack placement, etc.. 80% of the problems fall under prep & acid bath issues. I prefer lab grade glass temp sticks to monitor the bath vs digital. US standard vs Caswell anodizing methods differ. They're pretty much the same thing, but CW takes longer. We 12amps per SQ FT at 15v for 1 hour duration. Perfect wet black (pic below) requires longer ano time and is harder to achieve than color. Try a spray tank, dunk tank and Di tank for all tanks. For a low temp seal that might be too much, check your sheets for recommended temps. This will burn the seal out fast if only 180 is recommended. WD40 will bring the parts to a shine without a doubt, but if a part is burnt it's burnt. AnoWD40 also know as the "burned part fixer upper". George PM me your email


    Before


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    Thanks! Tried to PM you my email, said your inbox was full.



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    Sorry I forgot we only get 5 emails per account, please try again.



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    Update:

    I ran a second batch of parts yesterday with new sealant and a DI dunk tank between dying and sealing. It worked well, and I checked on the parts every 5 minutes. At the 15 minute mark, I noticed a little bit of white residue forming on a part, so I took all parts out of the sealant tank. Performed an alcohol test, parts were good and sealed. This morning played around with the cured parts and am 100% confident that the sealing process took.

    I now think that the white residue was ultimately due to the fact that I had left parts in the sealant for too long (30 minutes) in the previous batch. The bloom was probably made much worse by cross contamination.

    That is just my opinion based on this observation, if anyone has a more informed opinion, I'd love to hear it.



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