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Retaining shine/polish post anodize (6061)

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  • Retaining shine/polish post anodize (6061)

    I've been anodizing for about 6 yrs now and have a pretty good handle on the process. However one thing I've never been quite satisfied with has been the loss of shine of the parts. I'd like to achieve a very shiny finish, but end up with something closer to satin.

    Interestingly, at one point I received a batch of parts from a supplier, and during anodizing, they did not turn the typical golden champagne color. As a matter of fact, they did not change color at all, instead retaining their silvery mirror finish post anodize. The process wasn't to blame as I would anodize these parts with other material from a different batch, and those parts would turn the typical champagne color. Additionally, the parts reacted differently to stripping, where my typical parts will smut up and become quite dull during stripping, these showed no sign of smut and even retained most of there polish post strip.

    I had one of the parts sent out for material analysis, and all component percentages came right in line with 6061, as shown below:

    Silicon------------ 0.67
    Iron---------------- 0.4
    Copper----------- 0.31
    Manganese------ 0.08
    Magnesium------ 1.0
    Chromium------- 0.09
    Nickel------------- 0.02
    Zinc---------------- 0.05
    Titanium---------- 0.03
    Lead--------------- 0.01
    Tin----------------- <0.01
    Beryllium--------- <0.01
    Vanadium-------- 0.01
    Zirconium-------- <0.01
    Aluminum-------- Rem.

    Here's a pic showing the difference between a typical part, and the "magical" batch. I've since long run out of that batch and have never received 6061 that exhibited this trait since.

    Anyway - does anyone have any tricks to retaining polish?

    I use the LCD method. Does hot anodizing which uses temps closer to the 85F range, a much higher acid concentration and current density, in addition to much shorter soak times help in this regard? Or are there additives that can be added to the bath to help if using the LCD method?

    Thanks in advance for any replies!

    Last edited by g8erh8er; 03-27-2018, 09:43 PM.

  • #2
    Click image for larger version  Name:	image_4790.jpg Views:	1 Size:	2.5 KB ID:	143444 I can't answer your question g8 but I can show you some 6061 I polished then anodised and maintained that shiny look.

    I can't get the image to come in full size right now but will try again tomorrow.
    Last edited by gardinhackle; 03-27-2018, 11:35 PM.


    • #3
      I appreciate it gardinhackle. They must be having an issue with their photo uploader. I had to post my pic to imgur and link it in order to get my pic to show full size.

      It doesn't matter if I shine something to a mirror finish during prep as the parts lose a lot of that shine. I think getting that magical batch ruined me, as now I know what's possible with 6061. Maybe I need to have my supplier try a different metal vendor.

      Here's a couple good example pics, pre vs post anodize. Granted, the pre isn't mirror finish, but decent enough. The thing is, I prepared the unicorn batch the same exact way as my other parts, heck even tumbled them at the same time, so there must have been something material wise that differentiated them from the others.


      • #4
        Ya, looking at the parts you have shown there is no doubt the metallurgy is different. Retaining shine is a mystery to me too but the only thing I have found is polishing to a brilliant shine and reducing my ano time to hold the shine.


        • #5
          Yeah - it was crazy to have such different results with that batch when it was 6061 just like all the rest of my parts. I wonder if there's a particular material component, that when higher or lower (but still within the 6061 range), allows a part to retain its shine - silicone?

          Whenever I get some free time, I'm going to experiment with the high temp, high current density method to see if it makes a difference. I've been avoiding it up to this point due to safety concerns regarding the higher acid concentration and not having a big enough power supply to ano a lot of parts.

          Anyway, while the bath time is greatly reduced, you're still forming the same layer thickness over that reduced time, so I'm not sure it will make any difference when it comes to retaining polish.


          • #6
            I have my doubts it will help with luster retention as the crystal growth is still the same just grown faster like you said, worth a try though. Let us know the results... . I sometimes ano reel seats for a rod builder that are supposed to be 6061 and they turn out much brighter than my stuff and when I ask the manufacturer he gives me a drone reply which makes me think that either he is aware of the situation and doesn't want to give up the secret or he just doesn't know. I know one thing, there are many factors that effect shine - everything from using carbide inserts when machining even the type of coolant used all the way to what media and compounds are used during vib finishing.


            • #7
              g8erh8er, I figured out the pic issue. Here's the image I wanted to show you regarding the level of shine I'm able to retain.....for what it's worth now...



              • #8
                That looks beautiful. What kind of gold dye is that?
                Talking about alloys the more Si there is the grayer the part. I read somewhere that iron makes it more foggy.


                • #9
                  Thanks Wes,

                  It's Gold S, the image appears a bit washed out here but it's got a clean vibrant look to it. I prefer it to all the other golds I've seen and used.


                  • #10
                    Originally posted by gardinhackle View Post
                    g8erh8er, I figured out the pic issue. Here's the image I wanted to show you regarding the level of shine I'm able to retain.....for what it's worth now...


                    Thanks for the pics gardinhackle. Beautiful reels by the way!

                    Please don't take offense to this, but I would still consider the finish you acheived to be satin. Maybe the pic doesn't fully portray the finished polish though.

                    With my magic batch, the parts had a wet look to them post anodize, like they'd been coated with clear enamel. You could literally see your face in the flat surfaces. With any other batch of 6061 I've ever done, the surfaces anodize nicely, but lose most of the reflective qualities they had prior to anodizing.


                    • #11
                      No offnese taken G8erh8er! The pic does not do it justice but I can tell you it's not so shiny as to see your reflection , I'm sure the parts you speak of are over the top shiny or you likely wouldn't have posted about them.


                      • #12
                        I wanted to update this thread with a post-anodize pic to show the stark difference in the post anodize shade of the "magic batch" vs. the typical 6061 I anodize. Interestingly enough, the magic batch appears to have been machined from more than one lot of raw stock, as not all of it stays shiny and silver post anodize. My hope is that one day some metallurgy/anodizing guru will see this post and know exactly what's going on here.

                        Something jogged my memory the other day, and I realized I had once ordered a batch of parts made from 6063 because it supposedly retains it's shine really well after anodizing. Well that's definitely the truth. The problem is that it's soft and very gummy to machine. Just difficult to work with overall. Anyway, this magic batch anodizes EXACTLY like 6063, but it obviously isn't according to the previously posted material analysis.

                        So without further adieu, check out the below pics. These parts were all anodized on the same rack and thus under the same conditions. The red box indicates my typical 6061 that turns a deep champagne color after anodizing. The blue box indicates the magic batch. No color change whatsoever from pre to post ano. If I dried it off, you'd think it was fresh off the CNC machine. The purple box also indicates the magic batch, but this part was obviously machined from a different lot of material. It turned a very slight shade of champagne which may be difficult to see in the pics.


                        • #13
                          This next picture shows both parts from the magic batch. The one on the left was in the blue box in the previous pic (no color change pre to post ano). The one on the right was in the purple box (slight champagne color). Notice the more vibrant coloring and shine on the part on the left.

                          This is what I'm after in my anodizing process - a vibrant, shiny part. Unfortunately with the 6061 I get, it's impossible to achieve, no matter how highly polished the part is prior to anodizing. Wish I knew what the secret was to these 6061 parts that retain their shine throughout the anodizing process. Maybe one day!


                          • #14
                            Very interesting G8erh8ter! Thanks for the update too. Might be a dumb question but if the material that retains it's shine is so desirable why can't you get it instead of the stuff you use?


                            • #15
                              I switched my manufacturing away from the supplier who machined these parts (China). The quality started becoming too hit or miss. I’m Made in USA now.