Patent ID: 8114527

Claim:
A highly corrosion-resistant, rust-prevention coating material comprising: one of an organic binder and an inorganic binder; and Zn-alloy particles, the Zn-alloy particles comprising Zn, 0.1 to 30 percent Mg, and unavoidable impurities, and having physical fragmentation faces and/or cracks of 0.01 μm or greater length, or cracks of 0.01 μm or greater depth, wherein a Mg solid solution phase and Zn—Mg intermetallic compounds are present at fracture facets and/or cracks, wherein the Zn-alloy particles are dispersed in the binder in an amount of 30 mass % or greater based on a mass of a dry coating film of the coating material, wherein (i) the Zn-alloy particles include: (i-1) fine-grain Zn-alloy particles having a peak grain diameter in the range of 0.05 to 5 μm, the fine-grain Zn-alloy particles having a grain-diameter distribution, a grain-diameter frequency distribution of the grain diameter distribution having a single peak and a tail on either side of the peak, and (i-2) coarse-grain Zn-alloy particles having a peak grain diameter in the range of 6 to 100 μm, the coarse-grain Zn-alloy particles having a grain-diameter distribution, a grain-diameter frequency distribution of the grain diameter distribution having a single peak and a tail on either side of the peak, such that a grain-diameter frequency distribution of all the Zn-alloy particles has the grain-diameter frequency distribution peak of the fine-grain Zn-alloy particles and the grain-diameter frequency distribution peak of the coarse-grain Zn-alloy particles; and wherein (ii) 5 to 99% in volume percent of the Zn-alloy particles are Zn-alloy particles have a diameter in the range of 0.05 to 5 μm.