Methods of determining corrosion activity coolant by imprints

Determining the cutting fluid corrosivity by imprint test

The method is based on the ability of cast iron to react with corrosive working cutting fluids forming coloured corrosion products.

1. Equipment, materials, reagents:

Laboratory balance of VLKT-500 type as per GOST 19491-14 or of other type with a weighing error of +/- 0.01 g;
Laboratory glass dish as per with GOST 10973-75, Ø 100 mm (Petri dish);
Two 1 or 2 ml pipettes as per GOST 20292-74;
Cast iron chips SCh 18-36 or SCh 21-40 as per GOST 1412-70 with the following dimensions: 3-7 mm long in expanded form, 2-5 mm wide, 0.4-0.5 mm thick;
Laboratory filter paper as per GOST 12026-76;
Corrosion-resistant spatula as per GOST 9147-78.

2. Test preparation.

Visually check the chips for corrosion without touching them. Storage period of the chips shall not exceed 2-3 weeks after their manufacture.

3. Test procedure.

Uniformly apply 2+/-0.1 g of cast iron chips to the round paper filter (Ø 50 mm) placed in a Petri dish using a spatula. Collect 2 ml of well mixed process emulsion or aqueous cutting fluid solution using a measuring pipette and wet the chips on the filter chip uniformly.

Cover the Petri dish with a lid and keep at room temperature for 2 hours. Keep the Petri dish away from drafts and sunlight.

Fig. 2. Cutting fluid corrosiveness grade (in points).

Then remove the chips and dry the round paper filter at room temperature. The tests shall conducted in parallel in two Petri dishes.

4. Test evaluation.

Working cutting fluid emulsion or aqueous solution shall be considered to be satisfactory if there are no corrosion spots on the filter paper. If there are corrosion spots (Fig. 2), assess the degree of corrosion as follows (Table. 10).

Fig. 2. Cutting fluid corrosiveness grade (in points).

Table 10. Assessment of the degree of the sample corrosion.

Point	Degree of corrosion	Filter appearance
0	No	No change
1	Traces	Up to three spots with a diameter of less than 1 mm
2	Mild	Spot with a diameter of greater than 1 mm
3	Moderate	As per the pattern shown in Fig. 2
4	Severe	As per the pattern shown in Fig. 2

The results of parallel determinations (degree of corrosion in points) should not differ by more than one degree of corrosion. A greater degree of corrosion shall be taken as the test result.