BS EN ISO 3892:2001 pdf – Conversion coatings on metallic materials — Determination of coating mass per unit area — Gravimetric methods

BS EN ISO 3892:2001 pdf – Conversion coatings on metallic materials — Determination of coating mass per unit area — Gravimetric methods.
1 Scope This International Standard specifies gravimetric methods for determining the coating mass per unit area of conversion coatings on metallic materials. The methods are applicable to ? phosphate coatings on iron and steel; ? phosphate coatings on zinc and cadmium; ? phosphate coatings on aluminium and its alloys; ? chromate coatings on zinc and cadmium; ? chromate coatings on aluminium and its alloys. The methods are applicable only to conversion coatings that are free from any supplementary coating such as oil, water or solvent-based polymers, or wax. The methods do not indicate the presence of bare spots or sites with thicknesses lower than the specified minimum in the measuring areas. In addition, the single values obtained from each measuring area is the mean thicknesses over that area. There can be no further mathematical analysis of this single value, e.g. for statistical control purposes. 2 Apparatus 2.1 Vessel, of glass or other appropriate material, in which the conversion coatings can be dissolved. 2.2 Analytical balance, capable of weighing to the nearest 0,1 mg, for weighing the test pieces under examination before and after dissolution of the conversion coatings. 2.3 Electrical equipment, for electrolytic dissolution (for chromate coatings on zinc and cadmium).
4 Reagents and procedures 4.1 General For the preparation of solutions, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. The sampling procedure shall be as specified in the product standard. 4.2 Phosphate coatings on iron and steel 4.2.1 Manganese phosphate coatings 4.2.1.1 Reagent 4.2.1.1.1 Chromium(VI) oxide (CrO 3 ), a 50 g/l aqueous solution. 4.2.1.2 Procedure Dry the test piece (area A, in square centimetres, see 5.1 ) and weigh it, to the nearest 0,1 mg, using the analytical balance (2.2) (mass m 1 , in milligrams, see 5.1 ). Then immerse the test piece for 1 5 min in the reagent (4.2.1 .1 .1 ), maintained at 75 ?C ? 5 ?C. Rinse the test piece immediately in clean running water and then in distilled water; dry rapidly and reweigh. Repeat the procedure until a reasonably constant mass (differing by < 0,1 mg) is obtained (mass m 2 , in milligrams, see 5.1 ). Use freshly prepared reagent for every test piece.
4.2.2 Zinc phosphate coatings 4.2.2.1 Reagent 4.2.2.1.1 Aqueous solution, containing, per litre, 1 00 g sodium hydroxide, 90 g ethylenedinitrilo tetra-acetic acid, tetrasodium salt dihydrate (EDTA tetrasodium salt) and 4 g triethanolamine. 4.2.2.2 Procedure Dry the test piece (area A, in square centimetres, see 5.1 ), and weigh it, to the nearest 0,1 mg, using the analytical balance (2.2) (mass m 1 , in milligrams, see 5.1 ). Then immerse the test piece for 5 min in the reagent (4.2.2.1 .1 ), maintained at 75 ?C ? 5 ?C. Rinse the test piece immediately in clean running water and then in distilled water; dry rapidly and reweigh (mass m 2 , in milligrams, see 5.1 ). Use fresh reagent for every test piece. 4.2.3 Iron phosphate coatings 4.2.3.1 Reagent 4.2.3.1.1 Chromium(VI) oxide (CrO 3 ), a 50 g/l aqueous solution. 4.2.3.2 Procedure Dry the test piece (area A, in square centimetres, see 5.1 ) and weigh it, to the nearest 0,1 mg, using the analytical balance (2.2) (mass m 1 , in milligrams, see 5.1 ). Then immerse the test piece for 1 5 min in the reagent (4.2.3.1 .1 ), maintained at 75 ?C ? 5 ?C. Rinse the test piece immediately in clean running water and then in distilled water; dry and reweigh. Repeat the procedure until a reasonably constant mass (differing by < 0,1 mg) is obtained (mass m 2 , in milligrams, see 5.1 ).
Use freshly prepared reagent for every test piece. 4.3 Phosphate coatings on zinc and cadmium 4.3.1 Reagent 4.3.1.1 Ammonium dichromate, solution in 25 % to 30 % mass fraction ammoniac. During preparation of the solution, its temperature shall not exceed 25 ?C. 4.3.2 Procedure Dry the test piece (area A, square centimetres, see 5.1 ), and weigh it, to the nearest 0,1 mg, using the analytical balance (2.2) (mass m 1 , in milligrams, see 5.1 ). Then immerse the test piece for 3 min to 5 min in the reagent (4.3.1 .1 ) at room temperature. Carry out this operation in a fume cupboard. Rinse the test piece immediately in clean running water and then in distilled water; dry rapidly and reweigh (mass m 2 , in milligrams, see 5.1 ). Use freshly prepared reagent for every test piece. 4.4 Crystalline phosphate coatings on aluminium and its alloys 4.4.1 Reagent 4.4.1.1 Nitric acid solution, mass fraction 65 % to 70 %.