Method for applying manganese phosphate layers

A method comprising applying a manganese phosphate layer to an iron or steel surface of a workpiece by contacting the iron or steel surface with a phosphating solution, wherein the phophating solution comprises:

• 0. 2 to 4 g/l of iron(II) ions;
• 10 to 25 g/l of manganese ions;
• 25 to 50 g/l of phosphate ions calculated as P2O5;
• 3 to 35 g/l of nitrate ions;
• and
• 0.5 to 5 g/l of nitroguanidine;
• said solution having 7 to 24 points of free acid, 50 to 140 points of total acid, and an S value of 0.2 to 1, and
• drying the workpieces to form a manganese phosphate layer having a minimum thickness of 2 microns and an average maximum roughness depth (Rz) of from 1.3 to 2.5 microns.