NATIONAL STANDARDS TCVN 5670:2007
ISO 1514:2004
PAINTS AND VARNISHES - STANDARD PANELS FOR TESTING
1. Scope of application
This standard specifies several types of reference panels and describes procedures for preparing reference panels prior to painting. These reference plates are used in routine test methods for paints, varnishes, and related products.
2. Steel plate
2.1. Material
The steel plate used for the test is normally to be made of mild steel, in the form of plates or bars. The steel used must be free from rust, scratches, discoloration, and other surface defects.
a) Type 1 steel is cold rolled of commercial quality, with a thickness of 0.60 mm to 1.00 mm. Type 1 steel is a suitable commercial quality cold rolled steel. Steel must have a matte finish, with a surface roughness (Ra) between 0.63and 1.65.
b) Type 2 steel is a completely quenched, cold-rolled steel with a sheet thickness of 0.75 mm to 0.80 mm. Type 2 steel is completely quenched cold-rolled steel. The sheet must have minimum surface roughness and discoloration. The surface roughness (Ra) of the steel should not exceed 1.2.
c) Type 3 steel is cold-rolled commercial quality with sheet thickness from 0.25to 0.60. Steel with a smooth surface, with a surface roughness (Ra) not greater than 0.51.
2.2. Preserve before preparation
Before preparation, the plate must be stored in good condition, free from corrosion.
2.3. Preparation by the solvent cleaning method
Wipe off excess oil from the plate and rinse thoroughly with a suitable solvent to remove all traces of oil.
2.4. Prepare by water cleaning method (spray or soak process)
Clean the panels with a commercially available alkaline cleaning solution. Spray cleaning is recommended, however, immersion cleaning is also acceptable. Maintain detergent concentration and temperature according to the manufacturer's instructions.
2.5. Prepared by phosphate treatment
2.5.1. Treatment of crystalline zinc phosphate
This conversion coating method consists of reacting the steel surface in a solution of zinc acid phosphate with an oxidizing agent and a catalyst salt. The steel surface is changed to a crystalline phosphate coating to prevent corrosion, and increase the adhesion and durability of the paint film. This treatment can be applied by spraying, dipping or brushing with soft fiber nylon. The zinc phosphate coating has a characteristic gray to gray-white color.
2.5.2. Treatment of amorphous iron phosphate
This transformation coating method consists of reacting the steel surface in a solution of acid phosphate with an oxidizing agent and a catalyst salt. The steel surface is converted to an amorphous iron phosphate coating which increases the adhesion of the used coating and prevents corrosion to a lesser extent than the crystalline zinc phosphate coating. This treatment can be applied by spraying or dipping. The iron phosphate coating has a characteristic color range from yellow-green to violet.
Download: TCVN 5670:2007 PAINTS AND VARNISHES - STANDARD PANELS FOR TESTING
3. Zinc and zinc alloy coated sheet
3.1. Material
The reference plate shall be a cold-rolled carbon steel sheet coated with zinc or zinc alloy. The reference panels are not subjected to chemical passivation as this treatment will affect the adhesion of the coating.
An antirust passivation treatment, usually in the form of sodium dichromate solution, is applied upon rolling to prevent storage discoloration (or white rust) of the zinc-coated surface during storage. This antirust passivation, if not removed, affects the adhesion of the coating.
3.2. Preparation by the solvent cleaning method
For steel plates, if it is necessary to use clean plates without other requirements, use the cleaning procedure according to 2.3.
3.3. Preparation by the water cleaning method
For steel plates, if it is necessary to use clean sheets without other requirements, use the cleaning procedure according to 2.4. In general, detergent concentration, temperature, and contact time will be lower when cleaning galvanized steel. Detergents with high alkalinity will attack the zinc coating. For this reason, the lye used to clean galvanized steel should be within the pH range of 11 to 12.
3.4. Prepare by chemical treatment
3.4.2. Treatment of crystalline zinc phosphate
This conversion coating method consists of a zinc surface reaction in a solution of zinc acid phosphate with an oxidizing agent and a catalyst salt. The zinc surface is converted to a crystalline phosphate coating that prevents corrosion and increases the adhesion and durability of the used paint film. This treatment can be applied by spraying, dipping or brushing with soft nylon yarn.
3.4.3. Chromate treatment
This treatment consists of dipping or spraying with a specialized dilute solution containing chromium trioxide and other acids, together with a suitable accelerator. This treatment produces a thin amorphous chromate coating, which increases corrosion resistance and paint adhesion. This coating is not the same as that obtained when treated with an antirust passivator.
3.4.4. Treatment with chromium-organic solution
Water-soluble resins when properly mixed with chromium compounds can be applied to the zinc surface by a film roller or other suitable device, e.g. dipstick or rubber roller. The resulting coating is a corrosion-resistant film capable of increasing the adhesion of the applied paint film.
4. Aluminum plate
4.1. Material
The aluminum alloy plate used for routine tests shall be a plate or rod conforming to the chemical composition specification for Al Mn1Cu or Al Mn0,5Mg0,5 as specified in ISO 209-1: 1989. When other aluminum metal alloys are required for the test, the alloy shall be declared in the test report. The hardness shall be as specified for the particular test method. The thickness and other dimensions of the plate are specified in the test method or by other agreements.
Plates and bars must be free of cracks when a metal test piece, of a width of 20 mm and of suitable length, is cut to have a long side horizontal with the direction of a roll of the sheet, the long edge being rounded along the edge, bend 1800 for soft aluminum or bend 1800 in a cylindrical core with a radius equal to the thickness of the plate, for hard aluminum.
4.2. Preparation by the solvent cleaning method
For steel plates, if a clean sheet is required and not otherwise specified, use the cleaning method specified in 2.3.
4.3. Preparation by the water cleaning method
For steel plates, if a clean sheet is required and not otherwise specified, use the cleaning method specified in 2.4. Usually, the concentration, temperature of the cleaning agent, and contact time will be lower when cleaning aluminum. Furthermore, it is important to check that the alkaline cleaner chosen is safe for use with aluminum. Panels that have been cleaned by this method shall be free from intermittent standing water. This can be determined by immediately immersing the plate in distilled or deionized water.
4.4. Preparation by chromate conversion coating method
Aluminum plates or aluminum alloys prepared by chromate conversion coating for use in routine testing shall be prepared in accordance with ISO 10546.
Aluminum shall be cleaned as specified in 5.2 or 5.3. The chromate-transformed coating must be applied using a commercially available pre-treated chemical preparation. The water used to make the chromate solution shall at least comply with the class 3 requirements as specified in TCVN 4851:1989. Coatings range from light to yellow. The coating mass per unit area must be in the range of 0.1 g/m2 to 1.3 g/m2. The coating must be sticky and not powdery. Ideally, the coating should be completely homogeneous, free of stains and voids.
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