ISO 6370-2 Vitreous and Porcelain Enamels - Determination of Resistance to Wear - Part 2: Loss of Mass After Subsurface Wear

The standard "ISO 6370-2 Vitreous and porcelain enamels - Determination of resistance to abrasion - Part 2: Loss of mass after subsurface abrasion" developed by the International Organization for Standardization (ISO) describes a test method for determining the resistance of vitreous and porcelain enamel coatings to abrasion by friction, grinding or other mechanical effects.

The tests are based on the following principles:

Three identical enamel-coated test specimens and three reference glass plates are placed in the test machine.
Separated test samples and reference glass plates are simultaneously exposed to the abrasive action of a mixture of molten aluminum oxide grains, steel balls and water for three 30-minute periods each.
The relative wear rate is calculated from the average of the mass losses for three test specimens and three reference glass panes.

The following reagents are used to clean test samples and reference glass plates:

Ethanol (96 to 98 percent by volume)
Distilled water or water of equivalent purity (third class water conforming to the requirements of the ISO 3696 standard)

The device used in these tests is an abrasion tester that complies with the requirements of the ISO 6370-1 standard. This device includes the following parts:

Scale with 0,2 mg precision.
Pipette with a nominal capacity of 25 mL, at least class B, in compliance with the requirements of the ISO 648 standard.
Drying oven capable of maintaining temperatures of at least 130 degrees.
Dryer with an inner diameter of 200 mm.
Reference glass plates are square plates of float glass with a side length of 100 mm and a thickness of 3 mm. A set of three reference glass plates is required for each test. The specification of the float bath surface of the glass plates is complied with in the annex of the standard (Annex A). Float glass is a process in which a strip of hot glass is floated on a heated liquid of a density higher than that of the glass.

Materials used in these tests include:

Steel balls: For each test on a set of three specimens and three reference glass plates, the following are required: a 4 g ball with a diameter of 500 mm, a 3 g ball with a diameter of 400 mm and a 2 g ball with a diameter of 250 mm. The balls shall consist of stainless steel of the type used in bearings and shall be hardened (e.g. type 683 steel conforming to the requirements of ISO standard 17-20).
Abrasives: Fused aluminium oxide grains with a grit size of P 80, complying with the requirements of ISO 6344-2 standard.

When starting the tests, test samples are prepared in accordance with international standards for the appropriate base metal. The production of samples for testing vitreous and porcelain enamels for sheet steel and cast iron is specified in the ISO 28722 standard. Each test sample and reference glass plate are rinsed with water and thoroughly wiped with ethanol. The test samples and reference glass plates are dried in a drying oven at 120 degrees plus/minus 5 degrees for 2 hours. They are removed from the oven, kept in the dryers for at least 2 hours and each sample is weighed to the nearest 0,2 mg (initial mass).

A test is performed with each set of at least three test specimens and three reference glass plates. The test specimens and reference glass plates are fixed to the oscillating table of the abrasion tester by means of retaining rings, sealing rings and clamping devices so that the cover coat sides of the test specimens and the float bath surface of the reference glass plates face the inside of the retaining rings.

Each retaining ring is filled with an abrasive charge and plugged. The abrasive charge consists of: 4 g steel ball 80 mm in diameter, 3 g steel ball 60 mm in diameter, 2 g steel ball 35 mm in diameter, 20 mL plus/minus 0,2 mL of water, and 3 g plus/minus 0,01 g of abrasive.

The limiting deviations in mass for balls are the mass of each ball.

The oscillating table of the abrasion tester is operated for 30 min plus/minus 1 min, i.e., for a period corresponding to 9000 rotations plus/minus 300 rotations. Then, the samples and reference glass plates are removed and the test samples, reference glass plates, retaining rings and sealing rings are thoroughly rinsed under running water. The test samples and reference glass plates are air dried and placed in the abrasion tester with a fresh abrasive charge. The steel balls can be reused after being thoroughly cleaned.

If the thickness of the enamel coating to be tested is less than 0,2 mm, it is recommended to weigh the test sample before the next test period. The oscillating table is operated for another 30 min and then the entire procedure is repeated a third time. If the tested vitreous and porcelain enamel coating has already disappeared, the test is interrupted.

After three 30-minute test periods, the test samples and reference glass plates are removed from the abrasion tester. Rinse them thoroughly under running water. The test samples and reference glass plates are dried in a drying oven at 120 degrees plus/minus 5 degrees for 2 hours. They are then left in the dryer for at least 2 hours and each weighed to the nearest 0,2 mg (final mass).

A porous surface of the test specimen after abrasion may cause an increase in mass due to the absorption of water. This phenomenon is noted in the test report.

Among the numerous tests, measurements, analyses and evaluation studies that our organization has carried out for businesses in various sectors, our organization also provides testing services defined in the standard “ISO 6370-2 Vitreous and porcelain enamels - Determination of resistance to abrasion - Part 2: Loss of mass after subsurface abrasion” with its trained and expert staff and advanced technological equipment.