BS 4641-103:2010 pdf download – Method for specifying Electroplated coatings of chromium for engineering purposes 3.2 Information to be supplied to the purchaser by the electroplater Before processing, the electroplater shall inform the purchaser of visible surface defects such as porosity, cracks or undesirable coatings that are revealed by preliminary visual inspection and will prevent the production of a satisfactory electroplated finish. NOTE Guidance is given in A.3. 4 Sampling If specified by the purchaser [see 3.1.2 f)], samples for test purposes shall be selected in accordance with the procedures given in BS 6001. NOTE The choice of a suitable sampling plan should be agreed between the purchaser and the supplier. 5 Treatment of basis metals before electroplating 5.1 Stress relief If the purchaser specifies that stress relief treatment is required [see 3.1.1 d)], the necessary heat treatment shall be carried out in accordance with Appendix B. 5.2 Shot peening 5.2.1 If the purchaser specifies that shot peening treatment is required before electroplating [see 3.1.1 e)], the peening intensity, measured in accordance with Appendix C, shall be in accordance with Table 2 unless more specific requirements are stated on the drawing or in the peening schedule. 5.2.2 Freshly treated surfaces present conditions particularly favourable to corrosion. The first stage of electroplating shall therefore commence within 2 h of peening or, if this is not possible, a temporary protective coating shall be applied. 6 Coatings 6.1 Properties of regular chromium 6.1.1 Appearance. Inspection of the coating [see 3.1.1 j)] shall be by normal or corrected vision to evaluate the significant surface for freedom from defects such as pits, cracks, blisters, exfoliation and nodular growths, except as are tolerated by the purchaser [see 3.1.2 b)]. 6.1.2 Surface roughness. If a final surface roughness is specified by the purchaser [see 3.1.2 c)], the method of measurement shall be in accordance with BS 1134-1. NOTE 1 As a guide, for ground finishes, 0.4 4m R a may be regarded as a “commercial finish” and 0.2 4m R a as a “good commercial finish”. NOTE 2 Chromium, being brittle, has to be ground carefully with care being taken not to generate local hot spots or to induce cracking. NOTE 3 Chromium can be readily polished or lapped to improve surface finish. Super finishing can produce reflective surfaces of 0.05 4m R a . 6.1.3 Thickness. The minimum local thickness, as defined in BS 5411-1, of...
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