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Part not accepting dye.

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  • Part not accepting dye.

    I have a 220gm/L sulphuric solution which I have been using to anodise and colour some parts , to date I have only done 4 parts but it has always been at night so temps are in the mid 20deg range , today I did the same part and it will not accept dye after 60 mins of anodising 5A CC set at 12v , the difference to previous jobs is the ambiant temp is in the low 30s deg , is this enough to stop the anodising forming or do I have some other issue. Each job has 2 parts so I dont think its a connection issue as both failed and they had reasonable connections. previously I only need the parts in the dye @60 deg for 45 secs to get a intense colour . will too much current cause this issue ?

  • #2
    After doing more research it looks like I am at a 22% solution , for a current density of 6 is that too strong a solution - could that be the issue ?


    • #3
      220g/L is too high. If you are going to run with the industry standard (12 ASF) then adjust your electrolyte back to 180 g/L.


      • #4
        I dropped it back to 160g/l with no noticable change in outcome


        • #5
          Well 160g/L is not optimal either. Sounds like you have many issues that need to be resolved, starting with understanding the importance of accuracy with chemistry.

          If you are truly serious about resolving your problems then write out every step you are doing including all chems, strengths, temps, times, cleaning and so on. Basically every step of your process and we'll try to see what's going on.


          • #6
            Setup is ,

            anodozing tank has 7.5L of battery acid which is 460g/l and 15L of distilled water , at ambiant temperature of 24 deg C with a external tank around holding 40L of water as heat sink.

            Caswell degreaser at 60 deg C

            Caswell aluminioum brightener

            3 buckets of water for rinsing

            power supply contant current 10A 30v capacity.

            My process is on 6061 aluminium machined , clean with acetone then rinse , place in degreaser for 2min then rinse , repeat degreaser for 3 mins then rinse. place in aluminium brightenere for 2 mins then rinse.

            Set power supply to 13V then place into current control at 1.1A 125cm2 part , place part in anodising solution and readjust to ensure 1.1A current control , turn on air agitation and leave for 1 hour checking it stays at 1.1A

            After a hour remove from anodising tank and rinse thoughly.

            Place in dye @ 60 deg for 1 min

            remove and rinse

            place in near boiling water and boil for 20 mins

            Parts have always anodised as it is hard and appears the right finish ,but will not always accept dye , it leachers off when rinsed nearly totally


            • #7
              i think a lot of my issues are electrical contact . i just did 2 small parts , one worked perfectly one didnt , both done at the same time so conditions are identical . useing the titanium wire from caswell but it is very thin and when made into a hairpin type clip and pushed into a 6mm thread it doesnt provide much spring to ensure a stiff contact.
              Ordered some thicker wire and titanium bolts to try and get a better contact.


              • #8
                The issue with your set up surrounds the electrolyte density. What method are you trying to achieve, industry standard of 12ASF or the LCD method? because each has their own bath weight and run time. I can't tell you anything about the LCD method as I've never run it because it takes far too much time. From what I understand from your post you aren't getting enough crystal growth to hold dye. Either change up to the LCD method or possibly try running longer in the tank with your set up now like maybe 2 hours.


                • #9
                  Happy to go with the 12asf , I have enough grunt in the power supply for more amps , I see conflicting electrolyte densitys as well as anodising times , happy to run longer but was worried that there was to small a pores. Been looking for a definitive guide but evryone seems to be first timers too.


                  • #10
                    Originally posted by Daniel Collins View Post
                    Setup is ,

                    Place in dye @ 60 deg for 1 min
                    Seems a bit lite on the time. Normally parts are in the dye for 15-20 at least.

                    Process control doesn't give you good quality, it gives you consistent quality.
                    Good quality comes from consistently doing the right things.

                    Process control systems for Anodizers
                    If a post helps you out LIKE the post
                    I'm not an Amateur Metal Finisher. I've just been around the industry for a dozen years or so helping and consulting when and where I can.


                    • #11
                      All my successful parts have been 1-2mins in dye , anymore than that and its way to dark , if it anodises properly 40 sec seems to be the consistant best vibrant colour


                      • #12
                        My dye time averages are different for each colour but 2 minutes is normal for grey and even less for black. The only colours I need more time in the tank are reds and blues.

                        Daniel, Look at the top right of your screen under "messages" I sent you a PM a few days ago.
                        Last edited by gardinhackle; 10-31-2019, 07:11 AM. Reason: Spelling error