Deionized water
49.5
49.975
49.85
49.85
49.85
49.85
50

Anthranilamide
1.0
0.05
0.05
0.05
0.05
0.05
—

1,2,4-Triazole
—
—
0.25
—
—
—
—

Benzotriazole
—
—
—
0.25
—
—
—

betaine
—
—
—
—
0.25
—
—

n,o(bistrimethy-
—
—
—
—
—
0.25
—

silyl)acetamide

Sum
100
100
100
100
100
100
100

Experimental Example 1. Evaluation for Thermal Oxidation

1-1. Measurement of Rate of Change of Electrical Conductivity

Each of the coolant compositions (100 g) prepared in the Preparation Examples was added with 3 g of aluminum powder and then left at 60° C. for a long period of time (168 hours). After removing the aluminum powder therefrom, the compositions were measured for electrical conductivity, and the measurements are summarized in Table 2.

TABLE 2

Ex. 1
Ex. 2
Ex. 3
Ex. 4
Ex. 5
Ex. 6
C. Ex. 1

Electrical
Pre-
1.02
0.503
0.715
0.821
0.812
0.911
0.155

conductivity
test

Post-
3.14
2.14
2.18
2.41
2.43
2.65
1.01

test

Change rate (fold)
3.08
4.25
3.05
2.94
2.99
2.91
6.52

As can be seen in Table 2, the electrical conductivity was increased about 6.5 times in the coolant composition of Comparative Example 1 and about 3 to 4 times in the coolant compositions of Examples 1 to 6. Thus, the coolant compositions of Examples 1 to 6 were observed to exhibit remarkably low increase rates of electrical conductivity, compared to that of Comparative Example 1.

1-2. pH Change Measurement

Each of the coolant compositions (100 g) prepared in the Preparation Examples was added with 3 g of aluminum powder and then left at 60° C. for a long period of time (168 hours). After removing the aluminum powder therefrom, the compositions were measured for pH, and the measurements are summarized in Table 3.

TABLE 3

Ex. 1
Ex. 2
Ex. 3
Ex. 4
Ex. 5
Ex. 6
C. Ex. 1

Pre-test
6.1
5.9
5.9
5.8
5.7
5.3
5.6

Post-test
5.6
5.2
5.4
5.3
5.1
4.9
4.3

Change rate of
3.16
5.01
3.16
3.16
3.98
2.51
20.0