EAST AFRICAN STANDARD EAS 468: 2019 Pre-painted metal coated steel sheets and coils—Specification

1.Scope
This East African Standard specifies requirements, sampling and test methods for pre-painted metal coated steel sheets and coils.
2.Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references,the latest edition of the referenced document (including any amendments) applies.
EAS 11, Hot-dip galvanized plain and corrugated steel sheets — Specification
EAS 410, Hot-dip aluminium-zinc coated plain and corrugated steel sheets — Specification
ISO 15184, Paints and varnishes — Determination of film hardness by pencil test
ISO 15110, Paints and varnishes — Artificial weathering including acidic deposition
3.Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1 top (face) side
side of the pre-painted sheet, which is exposed to weathering
3.2 bottom (reverse) side
side of pre-painted sheet opposite the exposed weathering side
3.3 coating
continuous process by which paint and other coatings are applied and baked onto a metal coated flat steel sheet.
3.4 paint
organic liquid generally pigmented, which is converted to a solid film by baking
3.5 top coat
paint film on the surface which is exposed to weathering
NOTE
The topcoat provides colour and durability and also acts as protection against atmospheric corrosion. Different topcoats are selected based on the performance or appearance requirements desired.
3.6 primer
first complete layer of paint of a coating system applied to an uncoated surface; the type of primer varies with the type of surface and its condition, the intended purpose, and the coating system being used
3.7 wash coat
thin organic coating applied to the back or unexposed side of the pre-painted sheet (also known as a backer coat)
NOTE
The purpose of the wash coat is to provide protection against damage to the top-side coating during shipment and storage and also provide some additional durability to the unexposed side during the service life of the product.
3.8 chalking
formation on a pigmented coating of a friable powder evolved from the film itself at or just beneath the surface
3.10 fading
loss in colour intensity experienced by pigmented organic coatings over time, generally due to the effect of ultraviolet radiation
3.9 gloss
lustre, shininess or reflecting ability of a surface
3.10 sheets
broad, thin, mass or pieces of metal including flat and profiled
3.11 substrate
base material upon the surface of which an adhesive-containing substance is spread for coating
NOTE
The substrate is available in several different steel sheet qualities and with different metallic coatings as specified in clause 4, depending on the requirements of the purchaser. For the purposes of this standard, substrate refers to the steel sheet and metallic coating.
4. Substrate
The substrate shall conform to all the requirements of EAS 11 and EAS 410 as per appropriate specification for the quality ordered.
5.Classification and symbol
5.1 Classification of durability of paint coatings
5.1.1
The durability of paint coatings shall be classified into three classes and their symbols shall be as given in Table 1.

5.1.2
The classes of paint coating, durability for the face side and the reverse side shall be expressed in 2-digit figures consisting of a combination of the designation of durability for the individual sides.

5.1.3
For both-side paint coating for which the quality is guaranteed for the face only, the non-guaranteed side shall be expressed by the digit 0.

5.2 Classification of applications
5.2.1 Sheets and coils shall be classified into eight types, and their classified symbols shall be as given in Table 2.

5.2.2 For the type of coating and the coating mass on the metallic coated base metal for paint coating, EAS 11 and EAS 410 shall apply.
5.2.3 Coating systems supplied under this standard shall consist of primer coat covered by various types and thicknesses of topcoats except class 3. The combination of primer and topcoat shall be classed as either a two-coat thin film system or as a two-coat (or more) thick film system. The organic coating shall consist of a primer and a topcoat on the top (exposed) side and an optional wash coat on the bottom (unexposed) side that can either be tinted or non-tinted.
5.2.4 In the case of sheets and coils for roofing and architectural sidings the symbol R for roofing and the symbol A for architectural siding shall be suffixed to the classified symbols given in Table 2.
5.2.5 For sheets and coils subjected to corrugating, the symbol W and the shape symbol for corrugated sheets shall be suffixed to the classified symbols given in Table 2.
5.2.6 For corrugation, the commercial soft and the commercial hard qualities listed in Table 2 shall be used.
5.2.7 For roofing and architectural siding uses (exterior exposed building products) Class 2 or higher in the classification of paint coating durability shall be applied.
6. Paint coating durability
6.1 Sheets and coils shall be subjected to the durability test given in Table 3. The salt spray test shall be carried out in accordance with 13.2.1 and 13.4, and no defects, except for slight blistering and rust on the test piece, shall be found on the test piece as a result of this test having been continued for the duration of time specified in Table 3.

6.2 For class 3 in the classification of paint coating durability the symbol indicating a coating mass of D122 in accordance with EAS 11 (equivalent for other coatings) or more shall be applied to the base metal for paint coating.
6.3 When sheets and coils of Class 3 in the durability classification are subjected to the dew-cycle type accelerated weathering test in accordance with the provision of 13.2.2 and 13.4, they shall not show substantial discoloration, fading or substantial chalking as a result of the test having been continued for the duration of time specified in Table 3 (Delta E minimum).
7. Surface protective treatments
For protective treatments after painting when applied on the surface of sheets and coils, the types and symbols shall be as given in Table 4.

8. Physical properties of paint coatings
8.1 After being tested for items marked with “X” in Table 5 in accordance with 13.3 and 13.4, sheets and coils shall, by visual inspection, be free from the defects given in Table 5.

8.2 Test items for sheets and coils for roofing, architectural siding, and corrugation shall be in accordance with Table 5.
8.3 Paint adhesion and peeling shall be checked by applying standard filament tape.
9. Dimensions
9.1 The dimensions of sheets and coils shall be expressed in millimetres
9.2 The standard nominal thickness of sheets and coils shall be in accordance with EAS 11 and EAS 410.
10. Paint coating (dry film thickness)
10.1 Primer
The purpose of the primer is to serve as the bond between the substrate and the topcoat and to offer added corrosion protection for the entire system. The primer shall be compatible with the topcoat in order to ensure optimum properties of the coating system. For this reason, the primer is usually not specified by the purchaser but it is generally selected by the coating supplier or pre-painted sheet producer for optimum compatibility.
For building products, primer thickness shall be 5 µm with tolerance of ±1µm. High performance primers with films as thick as 75µm with tolerance of ± 8 µm may be specified.
10.2 Wash coat
For building products, wash coat thickness shall be 8 µm with tolerance of ±1µm.
10.3 Top coat
10.3.1 Different top-coats shall be selected based on the performance or appearance requirements desired.
For building products, top-coat thickness shall be 15 µm with tolerance of ± 5 µm. High-performance top-coats may be specified. Other upgraded systems may specify the application of two or more layers of top-coats.
10.3.2 The top-coat shall be applied for the exposed side of the sheet. However the unexposed side may be ordered with the same coating as the topside.
10.3.3 A wash coat or backer coat shall be applied to the bottom side.
11 Shapes
11.1 Camber
Maximum camber values for sheets and coils shall be as given in Table 6.

11.2 Deviation from squareness
Deviations from squareness for flat sheets shall be expressed by A/W x 100 (%) as shown in Figure 1 and shall not exceed 0.3 %.

11.3 Flatness

11.3.1 Flatness for sheets shall be as given in Table 7.

11.3.2 Flatness of sheets shall be determined as they are placed on a surface plate. The value shall be obtained by subtracting the sheet thickness from maximum deviation from the horizontal flat surface and the flatness shall be applied to the upper surface of the sheet.
12. Appearance
Sheets and coils shall be free from defects detrimental to practical use. However, in the case of coils, they may contain some minimal imperfections, including welds and floating.
13.Tests
13.1 General
The properties of the substrate and the organic coating system, combined with the method of forming,determine the life expectancy and general appearance of the final product. Each coating system has different qualities in regard to gloss, flexibility, fading, chalking, and resistance to cracking at bends, abrasion resistance, dirt retention, and resistance to varying atmospheric conditions. All of these factors should be considered in any end application. The test methods used to measure some of these parameters shall be in accordance with EAS 11 and EAS 410.
13.2 Endurance tests for coatings
13.2.1 Salt spray test
The salt spray test shall be done as follows:
a) a test piece shall be 50 mm or more in width and 100 mm or more in length; and
b) the testing method shall comply with ISO 11997-1.
13.2.2 Accelerated weathering test
The accelerated weathering test shall be as follows.
a) a test piece shall be 50 mm or more in width and 100 mm or more in length; and
b) the testing method shall comply with the accelerated weathering test specified in ISO 15110.
13.3 Tests for physical properties of paint coating
13.3.1 Sampling of test specimens
For corrugated sheets, test specimens shall be taken from flat sheets prior to corrugation.
Specimens shall be taken from products of the same quality, dimensions, coating mass, and color.
The sampling of test specimens for the T-bend, pencil hardness, impact, cross-scoring and abrasion (MEK) tests shall comply with the following requirements:
a) for continuously paint-coated coils or cut length from continuously paint-coated coils, one test specimen shall be taken from each 50 t or its fraction;
b) for sheets manufactured by paint-coating base metal cut to a specified length, one test specimen shall be taken from not more than 3 000 sheets;
c) apply zinc coating weight test for galvanized plain substrate;
d) apply aluminium zinc and silicon weight test for the 55 % aluminium zinc substrate; 
e) the testing method shall comply with the accelerated weathering test specified in ISO 15110.
13.3.2 Bend test
The bend test shall be as follows:
a) The test piece shall have a width of 75 mm to 125 mm and a length suited for the test. Unless otherwise specified, one test piece shall be cut out of each test specimen paralleled to the rolling direction of the base metal.
b) By referring to the internal spacing of bend shown in Table 8, the test piece shall be bent manually as shown in Figure 2.

c) The bend test shall be applied to the symbols indicating coating masses of Z 27 (equivalent for other coatings) and under. For sheets and coils using an alloyed type as base metal for paint coating, the above shall be used as reference only.
d) For sheets and coils for roofing, architectural siding, and corrugation, the internal spacing of bend shall be in accordance with that for, the relevant classified symbol in Table 8.

13.3.3 Pencil hardness test
The pencil hardness test shall be as follows:
a)a pencil having the hardness symbols given in Table 9 and meeting the requirements of ISO 15184 shall be used;

b) the pencil shall be sharpened so as to expose about 3 mm of lead. While being held at right angles to an abrasive paper of No. 400 or finer which has been laid on a hard, flat surface, the point of the lead shall be made to draw a continuous circle gently and thus be ground down so as to obtain a flat surface with sharp edges at the tip. The tip of the lead shall be ground flat for each test;
c) holding the prepared pencil at about 45º to the surface of the test specimen, straight lines shall be drawn with it in the direction shown Figure 3, with the load being applied of about 10 N;
d) the lines shall be not less than 20 mm in length and not less than three in number.

13.3.4 Impact test
The impact test shall be as follows:
a) a weight shall be dropped onto a test face from a Du Point type impact tester, as shown in Figure 4;
b) the mass of the weight shall be 500 g ± 1 g, and the radius of the impact point shall be 6.35 mm ±0.03 mm; 
c) the weight shall be dropped from a height of 500 mm above the test piece.

13.3.5 Cross-scoring test
The scoring test shall be as follows:
a) straight lines shall be scored with a safety razor blade or other pointed objects so as to reach the surface of the coating through the paint film and to form squares;
b) eleven straight lines shall be scored crosswise at right angles, at intervals of 1 mm.
13.3.6 Abrasion – Methyl Ethyl Ketone (MEK) test
13.3.6.1 Apparatus
The following apparatus and materials shall be used for the abrasion MEK test:
a) test piece (100 mm x 200 mm);
b) MEK ;
c) cheese cloth;
d) squeeze bottle; and
e) solvent resistant gloves.
13.3.6.2 Procedure
The abrasion test shall be done as follows:
a) select an area of the coated surface to be tested. Clean the area with tap water and a dry cloth. Mark a section of the cleaned area, measuring 150 mm by 25 mm with a solvent resistant marker, in which to perform the MEK double rubs; and
b) fold a 300 mm square piece of cheese cloth so that the thickness is doubled and saturate it until dripping wet with MEK. Place an index finger in the center of the cheese cloth and gather the remaining cloth. With the index finger at a 45° angle to the surface, rub with moderate pressure over the marked area. Do not allow more than 10 s to elapse between wetting the cloth and beginning to rub the coating. Wet the cloth as often as needed without lifting it from the surface. One forward and backward motion constitutes one double rub. Do a control test adjacent to the MEK test area. Use only a dry clean cloth rubbed in the same manner as the original test for the control test to establish the effects of the cloth on the coating.
13.4 Cautions for testing
The tests require the following cautions:
a) since the durability and physical properties of sheets and coils are affected by environmental conditions and by paint coating flaws incurred in handling, hair cracks on processed surfaces, etc.,testing shall be conducted on flat sheets with normal surfaces; 
b) the temperature for tests on physical properties shall be from 5 ºC to 35 ºC.
14. Inspection
Inspection shall be as follows:
a)the durability test is a performance test, and the test results shall comply with the requirements in Clause 6;
b)the results of tests and inspection on the physical properties of paint coatings, dimensions, shape and appearance shall satisfy the requirements specified in Clauses 6, 8, 9, 10, 11 and 12; and
c)when part of the test results for physical properties fail to meet the requirements, a retest using double the number of test pieces taken from the same lot is permitted.
15 Marking
15.1 Reverse side marking
15.1.1 For the sheets and coils which have passed inspection and the quality of which is guaranteed for one side only, the reverse side markings shall be as shown in Figure 5.
For both-side guarantees, the sheets and coils shall be marked only when so specified.
15.1.2 Each sheet or coil shall be legibly and indelibly marked.
15.1.2.1 For roofing, the following shall be indicated:
a) manufacturer’s name and/or trade name;
b) nominal thickness;
c) batch number;
d) designation of the substrate; and
e) paint coating class.
15.1.2.2 For other than roofing the following items may be indicated, upon agreement between the purchaser and the manufacturer:
a) manufacturer’s name or trade name;
b) nominal thickness;
c) classified symbol (including shape symbol for corrugated sheets);
d) batch number; and
e) designation of the substrate.
15.2 Package marking
Where sheets and coils are packed, each package shall be legibly and indelibly marked with the following information:
a) manufacturer’s name and/or trade name;
b) classified symbol (including shape symbol for profiled sheets);
c) name of colour;
d) symbol indicating coating mass;
e) dimensions; and
f) number of sheets or mass where applicable.
16. Storage, transportation and fabrication
16.1 Cautionary measures for storage, transportation, and fabrication shall be supplied with every sale in accordance with 16.2 to 16.4.
16.2 For the storage of sheets and coils, selection of a well-ventilated indoor place virtually free from dust and moisture should be specified. Mixed loading with corrosive substances such as chemicals should be avoided.
16.3 Every precaution should be taken against paint coating damage and contact with water during transportation and transfer.
16.4 The formability of paint coatings deteriorates with the descent of temperature. When sheets and coils stored in a low-temperature warehouse are to be fabricated, the temperature of the material should be elevated to normal temperature.
16.5 The indication of sheets and coils shall normally be made in terms of classified symbol, symbol for guaranteed side(s), symbol for surface protective treatments, symbol indicating coating mass, name of colour, and dimensions, as given in Figure 5 (a, b, c, d).