Anti-corrosive conversion coating compositions are disclosed. The anti-corrosive conversion coating compositions include a biopolymer and a rare earth element compound. Implementations of the anti-corrosive conversion coating composition can include where the biopolymer includes chitosan, starch, inulin, dextran, pullulan, or a combination thereof. The rare earth element compound may include one or more of the lanthanide series of elements, scandium, yttrium, or a combination thereof. The rare earth element compound may include a hydroxide of a rare earth element, an oxide of a rare earth element, or a combination thereof. Coated articles and methods for applying the anti-corrosive conversion coating compositions are also disclosed.