Powder-coated wave-shaped guardrail panels are produced using galvanized powder coating technology (including rust removal, phosphatization, and passivation). After the workpieces are pre-treated, this phosphatized film can prevent rust and enhance the adhesion of the powder coating layer. The surface of hot-dip galvanized steel is smooth, and without the necessary surface treatment before powder coating, the coating is prone to flaking and peeling off. Therefore, proper surface treatment is indispensable.