PURPOSE: To provide the compsn. which is pollution-free and has an excellent rust-preventive ability and an excellent effect of suppressing the generation of blister of a coating film in particular by compounding a zinc oxide and calcium oxide at specific ratios with aluminum dihydride triphosphate.

CONSTITUTION: This rust-preventive pigment compsn. is compounded with a) the aluminum dihydride triphosphate/ b) the zinc oxide/c) the calcium oxide at 50 to 80/15 to 45/2 to 10 by weight with the entire part as 100. The rust- preventive ability is not sufficiently exhibited if the compounding ratio of the component a) is lower than the range described above. Conversely, strong acidity appears and the rust-preventive ability degrades if the compounding ratio is higher than the range. The strong acidity appears and the rust-preventive ability degrades if the compounding ratio of the component b) is lower than the range described above. Conversely, the rust-preventive ability is insufficient if the ratio is higher than the range. The effect of suppressing the blister of the coating film is insufficient if the compounding ratio of the component c is lower than the range described above. Conversely, basicity is too strong and the stability and rust-preventive performance of the coating material degrade if the ratio is higher than the range.