Announcement

Collapse
No announcement yet.

AnodizeDiscolor

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • AnodizeDiscolor

    Hello,
    So I'm new to anodizing but have built what I feel like is a nice line and managed to work out the bugs however I can't seem to figure out what's causing this one. The part looks fine through the process, all the way through sealing. Once it is rinsed and dry it looks like there are wet portions, or like when you over-paint something and the paint runs. (Picture attached).

    My process: Lye - Rinse1 - Anodize - Rinse2 - Dye - Seal - Rinse3 and dry. (I know that not a lot of detail, but I'm trying to be a bit concise)
    The parts are 6061, or 6063 (I honestly can't remember which but my understanding is that both are ideal for anodizing)

    I am not the manufacturer of these parts, or the owner. The owner has told me the manufacturer puts them through an "acid bath" before they are shipped but I need to get clarification from them of what that means. The "acid bath" is currently my prime suspect. Maybe causing some sort of change to the finish that doesn't show up until it's through my process. I think this mostly because the other pieces I've run don't show the same discoloration.

    I figured I'd post here to see if any of you have seen this type of thing before and had ideas/suggestions of what (if anything) might be causing it in my process.

    Thank you for your time,
    Jason

  • #2
    It looks like a finishing issue to me. A good test would be to strip one of those very parts and bead blast it with something like #10 beads. Then anodise it again, my guess is it will come out consistent.

    Please inform us of the results.

    Comment


    • #3
      I don't see a deox step in your process. After etching (Lye) you will typically have a smut build up which needs to be removed. This is typically done in an acid deox bath.
      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.

      Comment


      • #4
        Originally posted by KevinB View Post
        I don't see a deox step in your process. After etching (Lye) you will typically have a smut build up which needs to be removed. This is typically done in an acid deox bath.
        While I totally agree these parts should be desmut/deox, from my experiences any odd surface effect as a result of not deox/desmutting tends to leave the parts with a blotchy, more uniform pattern. The part in the image appears to look more like residual acid has been sitting the lower side as though they were tipped on their side after being pulled out of the acid bath left to dry.

        Comment


        • #5
          I've been told the manufacturer uses hydrochloric acid to clean the parts before shipping them. I've now asked for the part without that acid cleaning to see if that was the issue. I will also look into a desmut step after the lye step. It sounds like that may increase the quality even if the lack of it isn't the reason for this current issue.

          I will update in a few days after I can anodize the non-hydrochloric acid bathed part.

          Thank you,
          Jason

          Comment


          • #6
            In all my experience I have never seen HCl in and around aluminum anodizing. Chlorides and Aluminum don't play together well and will pit the parts, and is one of the biggest reasons not to use tap water in your process line. You also don't want to set the precedent that your customer sends you parts that have not been cleaned, and if they do, you should charge for cleaning. I would recommend you tell your customer that they clean the parts in a mild soap solution at elevated temperature before sending them.
            Last edited by KevinB; 10-14-2020, 11:38 AM.
            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.

            Comment

            Working...
            X