1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 4652 : 1995 Incorporat
2、ing Amendment No. 1 ICS 87.040 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Specification for Zinc-rich priming paint (organic media)This British Standard, having been prepared under the direction of the Materials and Chemicals Sector Board (I/-), was published under the au
3、thority of the Standards Board and comes into effect on 15 April 1995 BSI 1998 First published July 1971 Second edition April 1995 The following BSI references relate to the work on this standard: Committee reference STI/27 Draft for comment 93/508127 DC ISBN 0 580 23846 6 BS 4652 : 1995 Issue 2, Ju
4、ly 1998 Amendments issued since publication Amd. No. Date Text affected 10074 July 1998 Indicated by a line in the margin Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee STI/27, Paint systems for metallic substrates, upon
5、 which the following bodies were represented: Aluminium Window Association British Coatings Federation Ltd. British Railways Board British Steel Industry British Telecommunications plc Department of the Environment (Building Research Establishment) European Resin Manufacturers Association Galvanizer
6、s Association Institute of Corrosion METCOM National Federation of Painting and Decorating Contractors Oil and Colour Chemists Association Paint Research Association Society of Chemical Industry Steel Window Association Union of Construction, Allied Trades and Technicians Zinc Development Associatio
7、n The following body was also represented in the drafting of the standard, through a subcommittee: Zinc Pigment Development Associationi BS 4652 : 1995 Contents Page Committees responsible Inside front cover Foreword ii Specification 1 Scope 1 2 Normative references 1 3 Sampling 1 4 Containers and l
8、abelling 1 5 Requirements for the components of the paint 1 6 Composition 1 7 Performance requirements of the paint after mixing 1 Annexes A (normative) Determination of metallic zinc content 3 B (normative) Preparation of test panels 4 C (normative) Resistance to continuous salt spray 5 D (informat
9、ive) Advice on handling and use of paint 5 Table B.1 Blast-cleaned steel with shot abrasives and grit abrasives 4 List of references Inside back coverii BSI 1998 BS 4652 : 1995 Issue 2, July 1998 | | Foreword This British Standard has been prepared under the direction of the Materials and Chemicals
10、Sector Board. It supersedes BS 4652 : 1971, which is withdrawn. The first edition of BS 4652, and later published amendments, specified three types of zinc dust-containing coatings intended for use as anticorrosive primers for the protection of abrasive blast-cleaned steel surfaces. Experience in th
11、e use of these materials, improvements in the preparation of steel surfaces, and formulation developments of zinc dust-based primers, have indicated that simplification of the existing standard can be made by a reduction in the number of types specified. The method for determination of metallic zinc
12、 content (see annex A) is based upon a method used by Harcros Chemicals. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer i
13、mmunity from legal obligations.BS 4652 : 1995 1 1) Marking BS 4652 on or in relation to a product represents a manufacturers declaration of conformity, i.e. a claim by or on behalf of the manufacturer that the product meets the requirements of the standard. The accuracy of the claim is solely the cl
14、aimants responsibility. Such a declaration is not to be confused with third party certification of conformity, which may also be desirable. Specification 1 Scope This British Standard specifies requirements for rapid drying priming paints containing a high proportion of zinc, supplied as two compone
15、nts, which react chemically when mixed together prior to use. The paints specified are formulated for direct application to steel immediately after blast-cleaning to grade Sa 2 of BS 7079 : Part A1. These paints are generally supplied as welding and prefabrication primers for thin film application,
16、up to 25mm dry film thickness or , for higher build films, typically up to 75mm dry film thickness. 2 Normative references This British Standard incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the
17、text and the publications are listed on the inside back cover . Subsequent amendments to, or revisions of, any of these publications apply to this British Standard only when incorporated in it by updating or revision. 3 Sampling Representative samples of each component of the paints shall be taken a
18、s described in BS 3900 : Part A1. 4 Containers and labelling All containers shall have openings of sufficient size to allow adequate stirring and mixing and shall be clearly marked with the following information: a) name of the supplier or manufacturer; b) manufacturers code or trade name; c) batch
19、number; d) reference to this British Standard; i.e. BS 4652 1) ; e) statutory requirements and information as necessary; f) ratio in which base and curing agent components need to be mixed and mixing instructions. 5 Requirements for the components of the paint 5.1 Zinc dust-based component 5.1.1 Whe
20、n the base component in its original container is first examined not more than 6 months after manufacture, any settlement shall be readily dispersed by mechanical stirring. The storage temperature shall be between 5 C and 25 C. NOTE 1. After longer periods harder settlement may occur . NOTE 2. See a
21、lso annex D for gassing. 5.1.2 The zinc dust in the base component shall conform to BS 3982. NOTE. The maximum allowable limit for lead and cadmium are subject to national health and safety legislation and therefore the maximum level will be dependent upon the current legislation, and not necessaril
22、y the figure quoted in BS 3982. 5.2 Curing agent When the curing agent in its original container is first examined it shall be readily dispersed by stirring to give a homogeneous appearance. The storage temperature shall be between 5 C and 25 C. 5.3 Mixing ratio The proportion in which the base comp
23、onent and the curing agent are to be mixed shall be a simple ratio by volume. 6 Composition When tested in accordance with annex A, the composition of the mixed paint shall be such that the content of zinc metal in the dry film shall be not less than 85 % (m/m) of the cured paint film. NOTE. Commerc
24、ially available zinc dust contains small percentages of oxidized material and consequently total zinc metal (metallic zinc) content may be lower than total zinc (zinc dust) content. 7 Performance requirements of the paint after mixing 7.1 Application properties The paint shall be suitable for applic
25、ation by the method(s) defined by the manufacturer or supplier in technical data sheets for the product. 7.2 Preparation of test panels T est panels for 7.3 to 7.6 shall be prepared in accordance with annex B.BS 4652 : 1995 2 7.3 Appearance The dried paint film, when applied by the manufacturers rec
26、ommended method at the recommended rate, shall be continuous and free from cratering, pinholing, sagging, bittiness and cissing. Examination shall be by normal or corrected vision. 7.4 Hard-drying time (weldable and prefabrication primers only) When the paint film is applied at the recommended appli
27、cation rate (l/m 2 ) and tested by the method described in BS EN 29117 it shall be hard-dry in not more than 30 min. 7.5 Resistance to impact When the paint film is applied at the recommended rate to a steel plate 200 mm3 200 mm35mm and tested with the coating uppermost in accordance with BS 3900 :
28、Part E7, it shall show no signs of cracking, flaking or detachment when examined using normal or corrected vision. 7.6 Resistance to continuous salt spray When the paint film is tested in accordance with annex C, it shall show no signs of rusting, and blistering shall not exceed scale D3 (S2) of BS
29、3900 : Part H2 in density and size. NOTE. A white deposit may be formed on the surface: this is not evidence of corrosion of the steel.BS 4652 : 1995 BSI 1998 3 Annexes Annex A (normative) Determination of metallic zinc content A.1 Principle The uncured paint is diluted with a suitable solvent, foll
30、owed by centrifugal separation of the pigment from the sample and reduction of an acidic iron/copper reagent solution by the metallic zinc with titration of the reduced reagent with standard potassium dichromate solution. A.2 Reagents A.2.1 Water, of at least grade 3 purity conforming to BS 3978. A.
31、2.2 Methyl ethyl ketone. A.2.3 Acetone. A.2.4 Iron/copper reagent. Dissolve (100 5) g copper (II) sulfate heptahydrate in 1 l of water (A.2.1). Add 1250 ml 60 % (m/m) iron (III) sulfate solution and dilute to 2.5 l. A.2.5 Potassium dichromate 0.05 M. In an agate mortar, powder about 30 g potassium d
32、ichromate (analytical grade reagent). Place in a clean glass evaporating basin and heat in an oven at (105 2)8C for 2 h. Allow to cool in a desiccator. Weigh out accurately 29.4 g of the dried salt, to the nearest 0.1 mg, dissolve in water and make up to 2 l in a volumetric flask. Shake well. The re
33、actor for this reagent: is called the dichromate factor. mass taken 29.4190 Record the factor. A.2.6 Sulfuric/phosphoric reagent. Carefully add 250 ml concentrated sulfuric acid (r = 1.18 g/cm 3 )t o1l of water, cool and add 500 ml orthophosphoric acid (r = 1.65 g/cm 3 ). Dilute to 2.5 l. A.2.7 Indi
34、cator solution. Dissolve 0.2 g sodium diphenylamine sulfonate in water and dilute to 100 ml. A.2.8 Ammonium hydrogen carbonate. A.3 Apparatus A.3.1 Centrifuge tubes, 50 ml, of inert material. A.3.2 Laboratory centrifuge, capable of imparting a relative centrifugal acceleration of about 100 km s 22 .
35、 A.3.3 Mortar and pestle, agate. A.3.4 Air-ventilated oven, capable of being maintained at (105 2)8C. A.3.5 Glass evaporating basins. A.3.6 Volumetric flasks, 100 ml, 2 l and 2.5 l. A.3.7 Conical flask, quick-fit iodine type with stopper. A.3.8 Measuring cylinders, 100 ml, 250 ml, 500 ml and 1l . A.
36、3.9 Burette, 50 ml graduated to 0.1 ml. A.3.10 Precision balance, accurate to 0.0001 g. A.3.11 Desiccator. A.3.12 Magnetic stirrer bar. A.4 Procedure A.4.1 Carry out the determination in duplicate. A.4.2 Take a test portion of (1.2 0.1) g of the mixed paint. Place in a weighed centrifuge tube, M 1 (
37、A.3.1). Immediately weigh the tube and the test portion to the nearest 1 mg, M 2 . A.4.3 Add about 20 ml of a suitable solvent and stir thoroughly with a glass rod. Withdraw the rod from the tube, washing the rod with a small quantity of the solvent, and centrifuge the tube until there is a clear su
38、pernatant liquor. Decant and discard the supernatant liquor from the tube. A.4.4 Add further solvent to the tube and mix as described in A.4.3, taking care to disperse completely the solid matter. Repeat the centrifuging and decantation of the liquor. With the addition of methyl ethyl ketone (A.2.2)
39、, repeat the centrifuging and decantation for a third time. Finally add the acetone (A.2.3) in place of the initial solvent and mix as described in A.4.3. Centrifuge and decant the liquor as before. A.4.5 After ensuring that excess acetone has evaporated, place the centrifuge tube in the oven (A.3.4
40、) maintained at (105 2)8C. After 24 h transfer the tube to a desiccator and allow to cool to ambient temperature. Weight the tube and contents to the nearest 1 mg, M 3 . A.4.6 Measure 50 ml of the iron/copper reagent (A.2.4) into a 500 ml flask. Add approximately 12 g (a heaped teaspoon) of ammonium
41、 hydrogen carbonate (A.2.8). Wash down any reagent adhering to the side of the flask with water. Using a precision balance (A.3.10) weigh accurately (0.4 0.05) g of dried pigment into a suitable weighing boat. Record the weight, M 0 , to four decimal places. Drop the weighing boat carefully into the
42、 flask (A.3.7) (taking care to avoid touching the neck of the flask). Stopper and shake vigorously for about 1 min ensuring that the stopper is firmly positioned at all times.4 BSI 1998 BS 4652 : 1995 Issue 2, July 1998 | Three-quarters fill the lip of the flask with water. With care, gently release
43、 the stopper. Wash down the flask and stopper with water. Drop a magnetic stirrer bar (A.3.12) into the flask and stir for a minimum of 15 min. Add 50 ml of sulfuric/phosphoric reagent (A.2.6). Wash down the flask and stopper with deionized water. Add approximately 1 ml of indicator solution (A.2.7)
44、 and titrate with the potassium dichromate (A.2.5) using the burette (A.3.9) to a permanent purple end point. A.4.7 Perform a blank determination, i.e. repeat the procedure in A.4.6 without the pigment sample. A.4.8 Determine the content of the non-volatile matter of the paint in accordance with BS
45、3900 : Part B18. A.5 Calculation The percentage of metallic zinc in the dry film shall be calculated as follows. 3 Dichromate factor (A2 B)( M 3 2M 1 ) M 0 ( M 2 2M 1 )NV 3 1003 0.9806 where M 0 is the mass (in g) of the test portion of the dried pigment (A.4.6); M 1 is the mass (in g) of the centri
46、fuge tube (A.4.2); M 2 is the mass (in g) of the centrifuge tube together with the paint sample (A.4.2); M 3 is the mass (in g) of the centrifuge tube together with the extracted dried pigment (A.4.5); A is the volume (in ml) of 0.05 M potassium dichromate solution required for the sample (A.4.6); B
47、 is the volume (in ml) of 0.05 M potassium dichromate solution required for the blank (A.4.7); NV is the content of non-volatile matter (in %) of the paint (A.4.8). 0.9806 is the factor to obtain free zinc content. Calculate the mean of the two determinations and report the result to one decimal pla
48、ce. If the two determinations differ by more than 1 % from the mean, repeat the procedure (A.4) and disregard the original results. Annex B (normative) Preparation of test panels B.1 General Except where otherwise stated, the test panels shall be hot-rolled mild steel having the dimensions of 100 mm
49、3 150 mm3 5 mm, free from distortion and abrasive blast-cleaned on the test surface to grade Sa 2 of BS 7079 : Part A1. Profile assessments of the blast-cleaned steel shall be carried out using a visual comparator in accordance with BS 7079 : Part C1 and BS 7079 : Part C2 and the profile shall be as given in table B.1. Table B.1 Blast-cleaned steel with shot abrasives and grit abrasives Shot abrasives Grit abrasives Grade coarse (S) Grade medium (G) Profiles equal to segment 3 and up to but excluding segment 4 Profiles equal to segment 2 and up to but excludin
