The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Scale problem on the interior and exterior of the parts

WE have a process where it calls for our extruded basics to be annealed before machining. This causes a flaky, scale problem on the interior and exterior of the parts. Whatever is not machined retains this scale. We have to plate them zinc/chromate and have an impossible time removing the scale. Has anyone ever removed a scale like this. Possible origin from oil heated or baked onto the parts during the anneal process.

James D. Browning
HPE - Batesville, Mississippi, USA

---

I suspect you know the right answer and just want to hear someone confirm it :-)

Clean the oil off before heat treating the parts! An alkaline descaler may be the most powerful process approach to removing the baked on scale.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

---

Dear James,

If youre the guy doing the plating then you have as tough time. If youre the component mfr. then do your plater a favour by hot phosphating the parts prior to the annealing.

The hot phosphate ensures that the parts are oil free, and the phosphate coating will prevent any scale formation.

good luck !

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India