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Heat Treatment effects- nickel plating

We heat treated a nickel plated part at 750F for 1h and it appears to get magnetic. Any ideas?

Daliana Abreu
Researcher - Rochester, New York
2006

Your nickel coating should have been amorphous in as-plated condition. Heat-treatment at 750F (400�aC) for 1 hour might have induced crystallization of the amorphous phase and impart the magnetic property to the coating.

Ni-P and Ni-B coatings prepared by electro- and electroless deposition processes are non-magnetic in as-plated condition when the phosphorus and boron contents of these coatings are higher than 9 and 6 wt. %, respectively. Heat-treatment of these coatings at 750 °F (400 °C) for 1 hour, enables the conversion of amorphous phase to crystalline nickel and nickel phosphide/nickel boride phases. The crystalline nickel phase imparts the magnetic property to the coating after heat-treatment.

If you perform TGA study of your coating (using the free standing nickel foil) in presence of a horse-shoe magnet (by placing the magnet under the balance), you could clearly observe the change in magnetic flux when the coating gets crystallized upon heat-treatment.

T.S.N. Sankara Narayanan
- Chennai, Tamilnadu, India
(ed.note Nov. 2017: The good doctor has a fascinating blog at https://advancementinscience.wordpress.com)
2006

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