Credits to Raptvre and his steam guide:
https://steamcommunity.com/sharedfiles/filedetails/?id=29377...OOOH SHINY
Plate all valid weapons with Solafite
In order to be able to plate with solafite, you first need to find the blueprint. It can be found in Cave F. The device requires [11x Stick, 4x Gold Batteries, 7x Stones, 3x Wires, and 3x Turtle Shells] to be made. Each solafite session costs you 6 ore. While in use, the device will spawn a thunderstorm and a horde of mutants. Prepare ahead of time. These are all the weapons that can be plated:
Cross
Tactical Axe
Machete
Crafted Club
Firefighter Axe
Modern Axe
Pickaxe
Putter
Katana
Pistol
Revolver
Shotgun
Rifle
Guitar
You can also plate the Ancient Armor with a separate blueprint, but it's not necessary for this achievement.