My favorite type of nickel plating for home scale is nickel acetate. It can be as simple as a 6v lantern battery, a nickel guitar string, and some vinegar (though guitar wires make terrible electroplating electrodes since they break and fall (something this document says can be mitigating by using a titanium basket)).
I think it's tempting to get into kitchen chemistry but you can very quickly find yourself playing with things that should not be in your home. Having a baby has made me question a lot of my home experiments and made me realize how sloppy I was.
Great amounts that are absorbed into the blood would do no good. For many people, mainly for women, nickel may be an allergen, which is why nickel is not recommended for jewels or piercings or anything else that stays in contact with the skin.
I had to look up the cause, and it was because it used a high Nickel alloy for the tool steel.
I had not associated Nickel as particularly harmful, but... it's relatively nasty in regards to human health (particularly when inhaled in even small amounts).
So I was curious and scrolled down to page 81 in the linked document on this post - they do a fairly thorough walk through of the potential harms, and it's worth reading for the folks who do this at home.
I've copied the relevant regulatory warnings from the document here:
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¹Nickel salts (e.g., Ni sulphate, Ni sulphamate) carry the following human health hazard classifications under GHS: (Global Harmonized System): Acute Tox. 4 (H302: Harmful if swallowed and H332: Harmful if inhaled), Skin Irrit. 2 (H315: Causes skin irritation), Resp. Sens. 1 (H334: May cause allergy or asthma symptoms or breathing difficulties if inhaled), Skin Sens. 1 (H317: May cause an allergic skin reaction), Repr. 1B (H360: May damage fertility or the unborn child, developmental effects), Muta. 2 (H341: Suspected of causing genetic defects), Carc. 1A (H350: May cause cancer by inhalation route only), and STOT Rep. Exp. 1 (H372: Causes damage to respiratory tract through prolonged or repeated inhalation exposure). Nickel metal carries the following human health hazard classifications under GHS: Skin Sens. 1 (H317: May cause an allergic skin reaction), Carc. 2 (H350: May cause cancer by inhalation route only), and STOT Rep. Exp. 1 (H372: Causes damage to respiratory tract through prolonged or repeated inhalation exposure).
What is specific to nickel is that much more people, especially women, are allergic to it, in comparison with other common metals. Therefore surfaces covered with nickel or nickel alloys with high nickel content are not recommended for contact with skin.
This Youtube video is useful if you want to start from scratch:
https://www.youtube.com/watch?v=G-PtnwtOR24
1: I could have used stainless steel instead, but bending, drilling, and tapping stainless steel is a lot harder than doing this with regular steel.
It's a good thing that we replaced most of the people-facing platings with plastics, because those are some nasty metals. The one metal that we still use everywhere is zinc, that isn't a big issue.
But nickel in particular allows for a lot of possibilities on the plating color, including some very-high absorption blacks. (And I think all the high-absorption for solar radiation, low absorption for thermal radiation coatings are nickel based.)
For the galvanic protection of steel, like in marine ships, electrodes of zinc, or better of magnesium, are suitable.