Die casting magnesium enclosure-surface preparation 3

[podan]

Hi,

I preparing the drawing for a magnesium die casting enclosure of a medical hand held device. I know that the part will be made overseas and I would like to specify a set of standards to be followed to ensure a good quality of the product and to have some control over the chemicals and operations applied to the part. My intention is to have some notes as following:
1. Enclosure material: AZ91D
2. Cast treatment: machining, deburring, grinding, bead blasting
3. Cleaning (alkaline)
4. Activation (acid pickling)
5. Conversion coating (chrome free)
6. Finish painted (not decided yet what type of paint)
7. All processes to be RoHS complient.
Please let me know what standards should be specifed for these operations or if you work for a die casting company what notes you would like to see in the drawing.
I appreciate any feedback from you.
Thank you,
Dan Pop

 

[TVP]

ASTM D 1732 covers most of the cleaning/pretreatment items for painting Mg parts. ASTM B 480 is similar for electroplating Mg parts. ASTM B 879 covers non-electrolytic conversion coatings, and lists non-Cr versions. SAE AMS 2475 also covers protective treatments for Mg, but is really only suitable for aerospace applications. ASTM B 94 covers Mg die castings using alloy AZ91D.

 

[podan]

Thank you TVP.

 

[podan]

Hi,

Could anyone suggest a surface treatment for enclosure mentioned above? The hand held unit will be used in dental offices and will be exposed to heavy CaviWipes cleaning.
Thanks,
Dan

 

[CoryPad]

Pretreatment: Alodine 5200 from Henkel or MAGPASS-COAT from AHC Oberflachentechnik or Gardobond X4707 or OXSILAN from Chemetall.

Topcoat: epoxy powdercoat, try Interpon/Akzo Nobel

 

[podan]

Thank you CoryPad.
Dan

 

[WKTaylor]

USAF uses a product called PreKote for bare aluminum & magnesium surface prep [

http://www.pantheonchemical.com/prekote.aspx

]... in lieu of MIL-DTL-5541 Cl1a or Cl3

Also a baked finish (enamel or similar ceramic) may take long-term disinfectant cleaning best... however any mag alloy will prove "difficult".

Suggest using high purity control alloy AZ91E per ASTM B403 or equiv for maximum corrosion resistance.

Regards, Wil Taylor

 

[podan]

Thank you wtaylor.