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Anodizing Problem????

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  • Anodizing Problem????

    Hello to all who see,

    I am experiencing a weird problem. I folow all the steps to get to the anodizing tank properly. The anodinzing tank is where my problem starts. I have 1 gal battery acid to 3 gals of distilled water mix. The 600w dimmer swtich setup from the manual. A alum tank bar drilled and taped for the wires. When i get to this tank I have a small peice of alum. about 8" sq face value. My amps are at .5-.75 for such a small part. I set my timer for 1 1/2 hours and check up on it every half hour. After about an hour to an hour an 15 mins my titanium wire disolves at the water level.... I dont think i have anything wired wrong but can draw up a diagram for anyone who wants to see. pics i can take too. The first time this happened i did continue to the dyeing process and did sucsessfully dye the part.( a very thin layer i might add but it did dye)Any and all comments welcome. i will be trying alum wire tonite and will post any results in here.
    Thanks for your time,

  • #2
    For your 8 square inches on one side (16 for both sides) and you ignore the surface area of the edges (OK if the work is thin) 0.5 Amps will get you close enough to 4.5 A/sq.ft.

    The wire dissolving at the electrolyte level means that your electrical connection to the work is very bad, only the wire itself is making electrical contact with the electrolyte.

    Since the titanium wire is much harder than the aluminum work, it won't cold flow under pressure, with enough force, the aluminum work will. The connection here MUST be so solid it is literally liquid tight. If its not, the connection will fail.

    This will be much easier to do if you use aluminum wire, the softer the better. A cheap source ($12 / lb.) for this wire is, a pound of aluminum wire will last a long time. You can use any size between 18 AWG and 8 AWG, 14 AWG will probably be the easiest size to use.


    • #3
      Hello Again,

      Thanks for your input fibergeek. I did try alum wire last night with great results. I also tried the titanium wire again. I bought some #10-24 alum screws and screwed each peice tightly to the tank bar and wire. I still had the titanium wire disolve at 55 mins into the anodizing process. the part was able to be dyed but a very thin layer. The alum part with the alumwire came out great. I had no problems with this and the color looked to be pretty even. I guess i didnt read the warning lable on the carton of battery acid that said will disolve titanium wire under mild aggitation. lol I would say I have come to a close with this problem and appreciate your input.
      thanks again...


      • #4
        I'm glad to hear that you sorted things out.

        Actually, titanium has excellent resistance to sulfuric acid, much better than aluminum. What you saw was what happens even to titanium when subjected to enormous current density; the 0.5A that you applied was concentrated in that skinny wire and only where it was in the electrolyte. The resulting current density in the wire could have been 100's of A/sq.ft. You didn't have a connection to the work for more than a matter of minutes before the connection anodized and failed.

        It isn't the tank bar to wire connection, this isn't in the electrolyte. It's the wire to the work connection that makes trouble.

        You now understand why when we say the connections must be TIGHT we aren't kidding. This isn't limited to LCD, the higher the current density you anodize at the more severe this problem becomes.