The effects of the mode of preparation on the anticorrosion properties of Ca‐Zn and Mg‐Zn borophosphates

Twelve pigment compositions derived from the xCaO·(50−x)ZnO·20B₂O₃·30P₂O₅·(x=10, 20, 30) and yMgO·(50−y)ZnO·20B₂O₃·30P₂O₅·(y=10, 20, 30) systems were prepared. The synthesis was carried out either by the medium‐temperature process or by the high‐temperature process followed by cooling in air and an isothermal crystallisation of the glass obtained. The pigments prepared by the medium‐temperature process achieved better corrosion results in styrene‐acrylate coating formulations, whereas those prepared by the high‐temperature process achieved better results in alkyd‐resin coating formulations. The anti‐corrosion results for the Ca‐Zn pigments were better than those for the Mg‐Zn pigments.