EAST AFRICAN STANDARD EAS 410: 2005 Hot-dip aluminium-zinc coated plain and corrugated steel sheets-Specification.

This East African Standard specifies requirements for continuous hot- dip Aluminium-Zinc (AZ) coated plain and corrugated steel sheets for roofing, cladding, fencing, fabrication and general use. 
This standard does not cover the special purpose profiles. 
The Aluminium-Zinc alloy composition by mass is nominally 55% Aluminium, 1.6% Silicon and balance Zinc. 
The product is intended for applications where the corrosion characteristics of Aluminium coupled with those of Zinc are most desired. 
2. Definitions 
For the purpose of this standard, the following definitions shall apply: 
2.1 AZ Coated Sheets 
Steel sheets with a uniform coating of Aluminium-zinc applied by the hot-dip process. 
2.2.1 Corrugated Sheets 
AZ coated steel sheets, which are mechanically formed to obtain regular, sinusoidal profiles, as shown in Figure 1. 

2.4 Thickness 
The thickness of base metal 
2.4 Plain 
The flat or even sheets without any relief forms 
2.5 Pitch 
The distance between two corresponding and consecutive points on the corrugated steel sheet along its width 
3. General requirements 
3.1 Dimensions 
3.1.1 Expression of dimensions 
3.1.1.1 Width and length — The dimensions of width and length shall be expressed in millimetres. 
3.1.1.2 Thickness — The thickness of AZ coated plain and corrugated sheets shall be expressed in gauge*. When measured in accordance with clause 8.2.1,the corresponding thickness of base metal in millimetres shall be as specified in Table 1 
3.1.2 Width —The width of plain and corrugated AZ coated sheets when measured in accordance with 8.2.4 shall be as specified in Table 2. 
3.1.3 Length — when measured in accordance with 8.2.2 the length of sheets shall be as specified in Table 3. 
3.1.4 Squareness — when measured in accordance with 8.2.3 the distance between diagonally opposite corners of the sheet shall not differ by more than 10 mm. 
3.2 Profile 
3.2.1 Depth — The depth of corrugations shall be 18 mm ± 1.5 mm, when measured in accordance with 8.2.6. 
3.2.2 Pitch — The pitch of the corrugations shall be 76 ± 2 mm when measured in accordance with 8.2.5. 
3.3 Tensile Strength — The tensile strength of plain and corrugated AZ coated sheets when determined in accordance with 8.2.7 shall be not less than 300 N/mm2. The yield strength shall be not less than 210 N/mm2. 
3.4 Resistance to Bending — When tested in accordance with 8.2.8 the sheet shall not crack, flatter or splinter.
3.5 Freedom from Defects — The sheets shall be uniform, clean and free from defects that would adversely affect their use. 
3.6 Finish — Unless other wise desired by the purchaser, the AZ coated sheets shall have a normal spangle finish as a result of the unrestricted growth of alloy crystals during normal solidification of ‘Mill Finish’. 

4. Aluminium-zinc coating process -criteria of conformity 

4.1 General Requirement 
The steel sheets shall be manufactured in accordance with accepted current practice and shall be from rolled mild steel made by a suitable process and meeting the requirements of ISO 2566. The sheets shall be true to size, homogeneous, with no trace of discontinuity of the Aluminium-Zinc coating. They shall also be free from holes, tears, twists, cambers and damaged edges and corners. Corrugations shall be parallel to the edges of the sheets. 
4.2 Aluminium-Zinc (AZ) Coating 
4.2.1 The coating shall be carried out by the hot-dip process in a coating bath containing about 55% Aluminium, 1.6% silicon and the balance zinc. The minimum mass of AZ coating on the two sides of sheet and the corresponding thickness of coating on each side shall conform to the minimum mass of coating given in Table 4. 
4.2.2 The coating mass shall conform to the requirements presented in table 4 for the specified coating designation when tested according to methods specified in 7.1. The coating mass is the total amount of the AZ alloy including both sides of the sheet expressed in grams per square metre (g/m2). The coating mass is not equally distributed on both the product surfaces. However, it may be assumed that a coating mass of at least 40% of the value given in table 4 exists as minimum on each surface of the product. 
4.2.3 AZ coating adherence shall be such that there shall be no flaking or splintering in the finished AZ plain or corrugated steel sheets, when tested in accordance with 7.2 
4.3 Classification -AZ plain and corrugated steel sheets shall be classified into seven classes depending on the mass of AZ coating applied to meet different service and environmental conditions. 
The classes shall be as specified in Table 4.

5 MARKING 
5.1 Conforming Sheets 
Each AZ coated plain or corrugated steel sheet conforming to this standard shall be permanently and indelibly marked with the following: 
(i) Manufacturer’s name and / or trade mark. 
(ii) The thickness expressed in gauge with the word “GAUGE” in full 
(iii) The coating class of sheet 
(iv) The batch identification. 
5.2 Non-Conforming Sheets — All sheets not complying with the requirements of this standard shall be identified by cutting off the bottom right hand corner at least by 40mm along both edges diagonally. 
6. Sampling 
The following sampling procedure shall be applied in determining whether a lot complies with the relevant requirements of this Standard. The samples so taken shall be deemed to represent the lot. 
6.1 Sample for Inspection and Dimensional Tests — From the lot, take at random the number of sheets shown in column 2 of Table 5 relative to the appropriate grouping in column 1. 
6.2 Sample for other Tests — From the sample taken in accordance with 6.1 take at random one sheet. 

7 Testing for AZ coating 
7.1 Mass of AZ Coating 
7.1.1 Weight method —The steel sheets shall be weighed before AZ coating. They shall then be passed through the AZ coating process and weighed again at the end of the process. 
7.1.2 Chemical method — The method prescribed in Annex A shall be used. The results, in g/m2, shall meet the requirements shown in Table 4. 
7.2 Coating adherence test
The test shall consist of subjecting the test piece of deformation by bending in one direction. The test piece shall either be bent mechanically or gripped in hand-operated device (mandrels may also be used) and bent until the two legs of the test piece are parallel to each other, i.e. through 180 degrees. 
A second test piece shall be bent in the opposite direction. The sheets shall be bent round a diameter of 38mm. 
8. Inspections and physical test 
8.1 Inspection — The sample taken in accordance with clause 6 shall be inspected for compliance with 3.5, and 5.1. 
8.2 Dimensions. 
8.2.1 Thickness — Using a micrometer screw gauge or a pair of callipers, measure to the nearest 0.01 mm the thickness of each sheet in the sample at any point at least 10mm from an edge and end of the sheet after removing the coating as described in A.4 of Annex A. 
8.2.2 Length — Place each sheet in the sample in turn on a flat rigid surface. Measure to the nearest 1 mm the length of each sheet in the sample along the centre line of the sheet. 
8.2.3 Squareness — Place each sheet in the sample in turn on a flat rigid surface. Measure to the nearest 1 mm the distance between the diagonally opposite corners of each sheet in the sample and record to the nearest mm any difference between the two measurements on a sheet. 
8.2.4 Width 
8.2.4.1 Plain sheets 
Place each sheet in the sample in turn on a flat rigid surface. Measure to the nearest 1 mm across the width of the sheet.
8.2.4.2 Corrugated sheets 
Place each of the sheets in the sample in turn on a flat rigid surface and measure to the nearest 1 mm across the width of the sheet. Choose at random a cross-section of the sheet and if, because of the springy nature of the sheet, the underside of the downwards corrugations or troughs are not all in contact with the supporting surfaces, apply sufficient pressure to the upper surfaces of the sheet to bring the lower surface into full contact with the supporting surface. Ensure that the application of pressure causes no deformation of the sheet other than that needed to bring the corrugations into contact with the rigid surface. 
Place the width gauge appropriate to the type of sheet being tested across the sheet a chosen cross￾section and at rigid-angles to the sides of the sheets and adjust the gauge to fit firmly over the 
outermost corrugations. Determine whether the width of the sheet complies with the requirements of Table 2. Both edges of the corrugated sheet shall be turned upwards. 
8.2.5 Pitch 
With the sheet in contact with a flat surface, place a transparent graduated rule on edge across the sheet so that it rests perpendicularly on the crests of two adjoining corrugations far from the points of contact, and read the distance between them to the nearest 1mm. Repeat the process to improve your results and take the average of five readings.
8.2.6 Depth of Corrugations 
With the initial rule lying flat across the corrugations at the edge of the sheet, use another graduated rule or a pair of calipers to measure the perpendicular distance between the initial rule and the rigid support.
8.2.7 Tensile strength 
From the sample taken in Clause 6, prepare a tensile test specimen as described in A.4 of Annex A by cutting a strip of 30mm × 80mm, such that the length of the specimen is transverse to the direction of rolling of the sheet. The portion of sheet from which the test piece is cut shall be carefully flattened. Determine the tensile strength of the specimen as described Annex A. If the tensile strength of the test specimen fails the requirements of 3.3 prepare two further test specimens and determine their tensile strength. If both specimens comply with the requirements, discard the results of the first specimen, but if either of the additional specimen fails to meet the requirements, deem the sheet and the lot to be defective. 
8.2.8 Bend test and coating adherence test 
A test specimen selected in accordance with clause 6 and shall be prepared measuring 10mm wide and length 120mm. It shall be cut with its length transverse to the direction of rolling of the sheet. Carefully bend the strip round a drum of diameter 38mm (mandrels may also be used) until the edges of the specimen are approximately semi-circular. If the specimen flakes or cracks, prepare and test two further specimens in the same way. If both these tests specimen comply with the requirements of 3.4 and 3.5, discard the results obtained on the first specimen, but if either of the two, crack at the bend, deem the sheet and lot to be defective.