Etchant for Thin Film Media

[SFChong]

Hi,
I'm searching for the correct type of etchant for thin film media. I need to etch away the Chromium and Cobalt layers which underneatch layer is Nikel/Phosphorus and the base material is Al. I also briefly know that Hydrochloric acid and Nitric acid may work; but I need to retain the Silicon Oxide Particle/Material on the media surface. Thanks in advance.

 

[PEJD]

Hi SFChong,
have you made any progress on an etchant for thin film media.

I am also interested in this. My application is to chemically destroy the platters of hard drives as a means of secure disposal for redundant drives.

Regards,

Paul.

 

[kenvlach]

Hi,
For stripping Cr from (electroless) nickel, a 12.5 vol. % Hydrochloric acid solution (125 ml of 37 wt% HCl per Liter) is recommended. I do not know of a suitable solution for stripping Co from Ni, since these 2 metals are chemically similar.

To strip Cr, Ni, etc. from Al or SiO₂, use concentrated nitric acid (67-70 wt.%).

To also destroy the Al or SiO₂ substrate, include some HF with HCl & HNO₃.

For information on stripping metallic coatings from various base metals, see

http://www.metalfinishing.com/WZ/MetalFinishing/guidebooks/MetalGB_SurfaceTreatments/000016/show/

 

[SFChong]

Hi, Thank you very much to Kenvlach and Pual for your respond. Sorry for my late reply.

I worked on 37wt% HCl both no dilution and 50% dilution (during Feb till now). So far, this is a better ones. I have also tried on concentrated nitric acid (67-70 wt.%), the layer Cr,Co, Ni are being stripped off and left only the Al.

Kenvlach mentioned that to destroy the Al or SiO2 substrate, include some HF with HCl & HNO3. May I know the concentration and ratio ? Thanks.

Lastly, anybody knows the suitable solution for stripping Cobalt from Ni where the underneatch layer is Nikel/Phosphorus ? Thanks in advance.

Regards,
SFChong.