1、BRITISH STANDARD Metallic coatings - Porosity tests - Humid sulfur (flowers of sulfur) test * Co * The European Standard EN IS0 126871998 has the status of a British Standard ICs 25.220.40 BS EN IS0 12687:1998 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN IS0 126821998
2、 AmdNo. Date This British Standard, having been prepared under the direction of the Sector Board for Materials and Chemicals, was published under the authority of the Standards Board and comes into effect on 15 May 1998 Text affected O BSI 1998 National foreword This British Standard is the English
3、language version of EN IS0 12687:1998. It is identical with IS0 126871996. The UK participation in its preparation was entrusted to Technical Committee STI/37, Methods of test for meWc and related coatings, which has the responsibility to: - aid enquirem to understand the te*, - present to the respo
4、nsible internationaVEhropean committee any enquiries on the interpretaiion, or proposals for change, and keep the UK interests informed; - monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this commitke can be obxined on req
5、uest to its secretary. Cross-references Attention is drawn to the fact that CEN and CENELEC standards normally include an annex which lists nonnative references to internationai publications with their corresponing European publications. The British Standards which implement internationai or Europea
6、n publidons referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International standards Correspondence Index“, or by using the “Find“ facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary
7、provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN IS0 title page, the
8、EN IS0 foreword page, the IS0 title page, page ii, pages 1 to 9, the annex ZA page, an inside back cover and a back cover. ISBN O 680 29672 5 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM March 1998 ICs 25.220.40 Descriptors: see IS0 document English version Metallic coatings - Porosity tests -
9、Humid sulfur (flowers of sulfur) test (IS0 12687:1996) Revtements m6tailiques - Essais de porosit - Essai B la fleur de soufre par voie humide (IS0 128871996) Metailische berzuge - prIhing der Porositt - Na- Schwefeiverfahren (mit SchwefeiMMe) (IS0 128879996) This European Standard was approved by C
10、EN on 26 February lW8. CEN members are bound to campiy with the CENCENELEC Intemal Regulations which spulate the conditions for gMng this European Standard the status of a national standard without any alteration. Upto-date lists and Mbliogtaphical references concerning such national standards may b
11、e obtained on appiication to the Central Secretariat or to any CEN member. This European Standard exiss in three oftidal versions (English, French, German). A version in any other language made by transletion under the responsibility of a CEN member into its own language and notified to aie Central
12、Secreariat has the same it may be used as an under-support. The fixture and any supports shall not cover more than 20 % of the vessels cross-sectional area so that air movement (convection) within the vessel shall not be restricted during the test. 7.3 Glass dish, consisting of a petri or other shal
13、low dish approximately 150 mm in diameter to hold powdered sulfur. The dish may be supported above the constant-humidity solution with plastic blocks or floated on the liquid. The free space of the liquid surface shall be large enough to guarantee equilibrium conditions in the test vessel for the en
14、tire test period. 7.4 Air-circulating oven, capable of maintaining the test vessel at a temperature of 50 OC f 2 “C. 7.5 Thermometer or other temperature sensor, having a range of at least 40 OC f 1 “C to 60 OC f 1 OC, which can be kept in the test vessel during the test. 7.6 Dielectric-detector hyg
15、rometer, with a remote sensor probe that can be placed in the test vessel, for the range of 75 % to 95 % RH. 3 = lb2Libb Ob77773 b8b EN IS0 12687:1998 7.7 Optical stereomicroscope, magnification x 1 O. One eyepiece should preferably contain a graduated reticule for measuring the diameter of tarnish
16、spots. If fitted, the reticule shall be calibrated for the magnification at which the microscope is to be used. 7.8 Light source, incandescent or circular fluorescent. 8 Test specimen preparation Avoid any unnecessary handling of the specimens, and then handle only with tweezers, microscope lens tis
17、sue or clean, soft cotton or nylon gloves. Prior to the test, inspect the sample at x 10 magnification under the stereomicroscope (7.7) for any evidence of particulate matter. If present, the particles shall be removed by dusting with clean, oil-free air. Then, thoroughly clean the particle-free sam
18、ples by gently rinsing with solvents or solutions that do not contain CFCs, chlorinated hydrocarbons or other known ozone-destroying compounds, and air-dry with clean air. A hot, analytical-reagent- grade methanol, ethanol, denatured ethanol or isopropanol dip is often useful in speeding up the dryi
19、ng. The following procedure has been found to be useful in avoiding the use of chlorinated hydrocarbons: a) Keep individual specimens separated if there is a possibility of damage to the measurement area during the various cleaning steps. b) Clean the specimens for 5 min in an ultrasonic cleaner whi
20、ch contains a hot (65 “C to 85 OC) 2 YO aqueous solution of a mildly alkaline (pH 7.5 to 10) detergent. c) After ultrasonic cleaning, rinse thoroughly under warm running tap water for at least 5 s. d) Rinse ultrasonically for 2 min in fresh distilled or deionized water (see 6.1) to remove the last d
21、etergent residues. e) Immerse in fresh analytical-reagent-grade methanol, ethanol, denatured ethanol or isopropanol, and ultrasonically “agitate“ for at least 30 s in order to remove the water from the specimens. f) Remove and air-dry specimens until the alcohol has completely evaporated. If an aird
22、usting is used as an aid to drying, the air shall be oil-free, clean and dry. g) Do not touch the measurement area of the specimens with bare fingers after cleaning. Re-inspect samples under x 10 magnification for particulate matter on the surface. If particles are found, repeat the cleaning step. S
23、urface cleanliness is extremely important. Contaminants, such as plating salts and flakes of metal, may give erroneous indications of porosity. Omit the cleaning steps for samples having tarnish-inhibiting or lubricant coatings, or both, if it is desired to determine the efficiency of the coating in
24、 the reduced-sulfur atmosphere. For nominal porosity-testing purposes, prepare the specimens so that the measurement areas (.e. the significant surfaces) have optimum exposure to the test environment. 9 Procedure 9.1 Test vessel equilibration For the initial operation of the apparatus, prepare the t
25、est vessel (7.1) for equilibration for at least a 24 h period before the first specimen exposure. NOTE- paragraph in this subclause and subclause 9.2, item e). For all subsequent tests, the initial 24 h equilibration procedure does not have to be repeated, see also last 4 = lb2qbb7 b97772 5L2 EN IS0
26、 12687:1998 Place the test vessel in the oven (7.4) with the sample support (7.2) in place. Place the saturated solution of potassium nitrate (6.2) in the bottom of the vessel. To ensure that the solution remains saturated at 50 OC, add approximately 20 g/100 ml of additional potassium nitrate cryst
27、als to the solution at room temperature. Place the lid on vessel (do not seal it with grease), insert the thermometer or other temperature sensor (7.5) and the remote humidity probe (7.6) through the opening in the top of the lid (leave the stopper out), and set the oven control to 55 OC. During equ
28、ilibration, open the vessel occasionally and stir the contents. As the temperature in the vessel approaches 50 OC, as indicated by the temperature probe, adjust the oven temperature as needed to stabilize the vessel at 50 OC. Do not close the vent in the stopper as this may cause the relative humidi
29、ty to approach 100 %. Fill the glass dish (7.3) half-full with sulfur (6.3) (break up any large lumps), and place the dish on supports above the potassium nitrate solution or float the dish directly on the solution (see figure 1). Replace the lid and insert the vented stopper in the lid opening. Mon
30、itor the vessel temperature over several hours, and adjust the oven temperature as needed to keep the vessel at 50 OC 2 OC. When stability has been attained, and the relative humidity is in the 85 % to 90 % range, the apparatus is ready for insertion of the specimens. The system described in this se
31、ction, may be reused for many subsequent tests without replacing the chemicals, and will remain stable for up to 6 months as long as the chemicals do not become contaminated with corrosion products or dirt. If allowed to cool, the potassium nitrate mixture will solidify, but it will liquefy again wh
32、en the vessel is reheated and the solution stirred. Break up crusts and lumps of hardened potassium nitrate and stir into the slurry. Add a few millilitres of water (see 6.1 1 if necessary to return the solution to its original condition. rVented stopper 9.2 Test procedure Temperature and humidity s
33、ensor YU Sample support w II LFlowers of sulfur Undissolved nitrate potassium Figure 1 -Typical test equipment arrangement Bring the test vessel to equilibrium as described in 9.1. Place the clean specimens in the test vessel as rapidly as possible so as to minimize deviations from equilibrium condi
34、tions. Also place a clean, unplated copper or copper- alloy panel in the vessel each time a test is run to act as an internal control, that is to show that the test system is operative. The copper should start to darken within a few hours. a) During the first 1 h to 2 h of the test run, leave the ve
35、ssel slightly open, by removing the vented stopper, in order to prevent moisture condensation while the system is coming to the test temperature. When the test temperature is reached and the relative humidity is in the 85 % to 90 % range (which may take 1 h to 2 h), replace the vented stopper. 5 EN
36、IS0 12687:1998 b) C) d) e) During the first 2 h to 3 h of exposure, check the temperature and humidity in the desiccator and record it at suitable intervals in order to ensure the attainment of equilibrium conditions. Do the same towards the end of the test. Continue the test for the required time;
37、this shall be 24 h, unless otherwise specified. The test system may be left overnight (or over the weekend for a 3day test) without further monitoring. At the end of the test, remove the specimens, replace the vessel lid and allow the specimens to cool to room temperature before examining them. For
38、all subsequent runs, the operations described in 9.1 may be eliminated. However, routine checks of the actual temperature and humidity within the vessel shall still be made, and occasional stirring of the potassium nitrate solution may be required before a new run. 1 O Examination and evaluation of
39、specimens Examine the measurement areas at x 10 magnification under the stereomicroscope (7.71, using the light source (7.8). a) The presence of brown or black tarnish marks or spots indicates that the finish is porous at these sites down to the copper, copper-alloy or silver substrate. This tarnish
40、 tends to creep from the pores and enlarge the marks or spots over the test period. If the pore sites are to be counted, the following hints may be useful as an aid to counting: 1) Count only tarnish and corrosion products that are brown to black. 2) Do not consider loose contamination that can easi
41、ly be removed by mild air-dusting as tarnish or corrosion products. 3) Move the specimen around under the light to vary the angle to verify pore indications. Burnished gold can give the appearance of black spots. Measure and count a tarnish or corrosion mark or spot when at least three-quarters of t
42、he spot falls within the measurement area. Tarnish creepage films which start outside the measurement area but fall within it, shall not be counted. However, the presence of significant tarnish creepage shall be recorded and its location given. d) Pore size shall be defined by the longest diameter o
43、f the corrosion product. Unless otherwise specified, corrosion products smaller than 0.05 mm in diameter shall not be counted. A graduated reticule in the microscope eyepiece is useful as an aid to counting and sizing. NOTE- A useful sizing technique is to tabulate the pores in accordance with three
44、 size ranges: These are approximately a) 0.1 2 rnm diameter or less; b) between 0.1 2 rnm and 0,4 mm diameter; c) greater than 0.4 mm diameter. e) The acceptable number, size and location of these tarnish or corrosion marks or spots shall be as specified in the appropriate drawing or specification.
45、b) c) 6 Lb24bb9 b97774 395 EN IS0 12687:1998 Annex A (informative) Significance and use A.l Coating quality A major use of this test procedure is for determining coating quality. Porosity tests are indications of the completeness of protection or coverage offered by the coatings, since the coatings
46、described in clause 1 are intended to be protective. The porosity test results are, therefore, a measure of the deposition process control. A.2 Application to underplate quality A particular purpose of the humid sulfur vapour test is for determining the quality of underplates of nickel or nickel all
47、oy in those finish systems that have thin (1 pm to 2 pm or less) top layers above the nickel, since porosity in the underplate usually continues into such top layers. - A.3 Application to indoor environmental tarnishing = - The humid sulfur vapour test is often used as an environmental test to simul
48、ate many indoor humid atmosphere tarnishing and tarnish creepage effects. However, the chemistry and properties of these tarnish films may not resemble those found in other service environments. For such product performance evaluations, the test should - = _. - * m only be used in combination with o
49、ther performance evaluation tests, as specified in the referencing document for * that product. A.4 Relationship to ageing tests Porosity tests differ from corrosion and ageing tests, since the latter are intended to measure the chemical inertness of the coating. In contrast, in a good porosity test procedure, the corrosive agent should not attack the coating. It must, instead, clean, depolarize and/or activate the substrate metal exposed by the pore, and attack it sufficiently to cause reaction products to fill the pore to the surface of the coating. A.5 Sensitiv
