Hexagonal boron nitride (hBN) with outstanding impermeability and resistivity seems to hold promise as a long-term corrosion barrier for metals. However, the high-yield production of hBN still remains a key challenge. Herein, we provide a scalable exfoliation technique to scalable synthesis of hydroxylated boron nitride nanosheets (HBNNS). Then phosphorylated boron nitride (PBNNS) was prepared through in situ phosphate esterification between HBNNS and phosphoric acid. The PBN coatings were fabricated by electrophoretic deposition (EPD) from PBNNS suspensions for metal protection. The excellent corrosion resistance of PBNNS-EPD layers was attributed to the superior barrier property and formed passivation film from PBNNS.