Rusty axe head restoration I have an old axe head, kind of a family heirloom, that I want to clean and restore. Given its age (approx. 60-70 years) and condition, my goal is not to make it usable as an axe, but preservation and possibly use as decoration.

To be clear, there is no wooden handle, I'm only asking about the metal part.

I have started removing loose rust using sandpaper and WD-40. However, even where the loose rust is removed, the metal surface is very pitted, and I was unable to remove rust from these pits and indentations (some 1 to 5 mm in diameter).

I am asking for advice (and/or resources) on removing rust from this pitted metal surface. I don't need it to be 100% smooth and polished and shiny, but I want to prevent further rusting and give the old piece a decent look.
There are a number of "baths" one can use to clean the rust pretty thoroughly from a part you described. WD-40 makes a product which performs well in the YouTube videos I've seen. Pour a sufficient amount to cover the item in a plastic bin and let it soak. I understand from the videos that the smell of the used liquid is objectionable, so stand upwind.

Some agitation would improve the action, as well as higher temperatures. Perhaps leave it in the sun to assist the thermal aspect.

A quick search for rust removal liquid returns many options.

Once the rust is removed and the part is washed of the chemical, you can coat it with a polyurethane clear product or similar.