×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Anodising Problem

Anodising Problem

Anodising Problem

(OP)
Hi, I have had some aluminium parts water jet cut for a job, and needed them anodised.  I decided to try myself as there will be a slow but steady trickle of these parts to do and it is not economical to have them done professionally with minimum orders.

I set up a small rig along with tanks for the pre-cleaning operations etc, the main anodising tank is approximately 14" square and holds in the region of 2.5 gallons of sulphuric/water mix, approximately 13% acid.

In trials it was going quite well but the aluminium hangers I used (12g aluminium wire) would dissolve over 20mins when used with a decent current of say 10amps at 24v.  To get over this I made a titanium T shape hanger to hang 2 pieces on which did not dissolve of course- but I could not get a good connection between the titanium hanger and the test pieces, as soon as the power was connected and the first lot of bubbles had risen the connection would disappear, I put it down to the poor conductivity of the material as touching the hanger would make small sparks appear between it and the aluminium pieces, current would rise then disappear again.

I then made up a much thicker aluminium hanger (8mm diameter bar welded to 25x6mm flat bar in a T shape), the pieces to be annodised have 8mm holes though 3mm plate, all countersunk (so not much area in contact with hanger) but were a tight fit and pushed onto my new hanger.  When powered up though I could not get more than 2-3amps to draw through the set up which dropped to nothing and did very little.  When I took it out and popped a piece of 12g wire back in and connected it the current shot back up to 15amps.

I'm obviously overlooking something simple, but I have tired myself over the subject and can't think what.  If anyone has any advise it would be greatly appreciated.  The power supply by the way has 12/24v, 20/80a, but I can use resistive wire to lower the current which I did succesfully in testing.  The surface area of each workpiece is approx 14"sq.

RE: Anodising Problem

Anodizing is an electrically insulating coating. Ideally you should leave a small tab on your part so you can make your electrical connection above your liquid surface. If you use a hanger, it will be anodized as well, so if your part moves on the hanger the electrical connection will be poor.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources