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1、I ,?A, . I nternationa I Sta nda rd 2178 I . INTERNATIONAL ORGANIZATION FOR STANOAROIZATION8ME)t(JjYHAPOAHAR OprAHH3AHR no CTAHAAPTH3AHH80RGANISATION INTERNATIONALE OE NORMALlSATION Non-magnetic coatings on magnetic substrates - 8 Measurement of coating thickness -Magnetic method Revetements metalli
2、ques non magnetiques sur metal de base magnetique -Mesurage de /epaisseur du revetement -Methode magnetique Second edition -1982-08-01 8 I w UDC 669.058: 531.717 : 621.317.49 Ref. No. ISO 2178-1982 (E) Descriptors : meta! coatings, non-metallic coatings, vitreous enamels, porcelain enamels, dimensio
3、nal measurement, magnetic tests, base metal. cO r- N 0 Price based on 4 pages - I Foreword ISO (the International Organization tor Standardization) is a worldwide federation of national standards institutes (ISO member bodies). The work of developing Inter- national Standards is carried out through
4、ISO technical committees. Every member body interested in a subject tor which a technical committee hag been set up hag the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. Draft International
5、Standards adopted by the technical committees are circulated to 8 the member bodies tor approval before their acceptance as International Standards by the ISO Council. International Standard ISO 2178 was developed by Technical Committee ISO/TC 107, Metallic and other non-organic coatings, and was ci
6、rculated to the member bodies in November 1980. It hag been approved by the member bodies of the following countries: Australia Italy Sweden Bulgaria Japan Switzerland Czechoslovakia Netherlands United Kingdom France Poland USA Germany, F. R. Romania USSR Hungary South Africa, Rep. of India Spain No
7、 member body expressed disapproval of the document. e This second edition cancels and replaces the first edition (i.e. ISO 2178-1972). “ International Organization tor Standardization, 1982 . Printed in Switzerland INTERNATIONAL STANDARD ISO 2178-1982 (E) I . I Non-magnetic coatings on magnetic subs
8、trates - Measurement of coating thickness -Magnetic method 1 Scope and fjeld of application 4.2 Magnetic properties of the basis metal This International Standard specifies the method of using Thickness measurements by the magnetic method are affected coating thickness instruments of the magnetic ty
9、pe tor non- by variations in the magnetic properties of the basis metal. For destructive measurements of the thickness of non-magnetic practical purposes, magnetic variations in low carbon steels coatings (including vitreous and porcelain enamel coatings) on can be considered to be insignificant. To
10、 avoid the influences magnetic basis metals. of several, or localized, heat treatments and cold working, the instrument should be calibrated using a calibration standard The method is applicable only tor measurements on reasonably having a basis metal with the same properties as that of the test fla
11、t specimens. In the Gase of nickel coatings on non-magnetic specimen or, preferably, and if available, with a sampie of the substrates, the preferred method is that specified in ISO 2361. part to be tested before application of the coating. 2 References 4.3 Basis metal thickness ISO 2064, Metallic a
12、nd other non-organic coatings -Defini- For each instrument, there is a critical thickness of basis metal tions and conventions concerning the measurement of above which measurements will not be affected by an increase thickness. in thickness. SinGe it depends on the instrument probe and the nature o
13、f the basis metal, its value should be determined ex- ISO 2361, Electrodeposited nickel coatings on magnetic and perimentally, unless it is specified by the manufacturer. non-magnetic substrates -Measurement of coating thickness -Magnetic method. 4.4 Edge effects 3 Principle The method is sensitive
14、to abrupt changes in surface contour of the test specimen. Therefore, measurements made tao near an Coating thickness instruments of the magnetic type measure edge. r inside .corner will not be valid unless the instrument is either the magnetic attraction between a permanent magnet speclflcally call
15、brated tor such measurment. he effect ay and the basis metal, as influenced by the presence of the extend .up to about 20 mm tram the dlscontlnulty, dependlng coating, or the reluctance of a magnetic flux path passing on the Instrument. ,8 through the coating and the basis metal. 4.5 Curvature 4 Fac
16、tors affecting the measuring 1) Measurements are affected by the curvature of the test accuracy .Th.flfdbl.hspeclmen. ein uence 0 curvature va rIes consl era y Wlt Thf 1I.ftfft thfthe make and type of instrument, but always becomes more e 0 owlng ac ars maya ec e accuracy 0 measure- . tft.th.kpronou
17、nced as the radius of curvature decreases. men s 0 coa Ing IC ness. Instruments with two-pole probes mayaiso produce different 4.1 Coating thickness readings if the poles are aligned in planes parallel or perpen- dicular to the axis of a cylindrical surface. A similar effect can The precision of a m
18、easurement changes with coating occur with a single-pole probe if the tip is unevenly warn. thickness depending on the instrument design. For thin coatings, the precision is constant, independent of the Measurements made on curved test specimens may not, thickness. For thick coatings, the precision
19、is an approximately therefore, be valid unless the instrument is specifically constant fraction of the thickness. calibrated tor such measurements. 1) For the purpose of this International Standard, the measuring uncertainty is defined as that obtained with an instrument correctly calibrated and use
20、d. 1 - ISO 2178-1982 (E) I . 4.6 Surface roughness an instrument probe in a horizontal or upside-down position may require a different calibration, or may be impossible. If the range of aseries of measurements, made within the same reference area (see ISO 2064) on a rough surface, substantially exce
21、eds the inherent repeatability of the instrument, the number of measurements required should be increased to at 5 Calibration of instruments least five. 5,1 General 4,7 Direction of mechanical working of the basis metal Before use, each instrument shall be calibrated in accordance with the manufactu
22、rers instructions using suitable calibration Measurements made by an instrument having a two-pole probe standards or by comparing magnetic thickness measurements or an unevenly warn single-pole probe may be influenced by made on a selection of the test specimens with thickness the direction in which
23、 the magnetic basis metal hag been sub- measurements made by the method specified in the Interna- jected to mechanical working (such as rolling), the reading tional Standard tor the particular coating concerned. For in- changing with the orientation of the probe on the surface. struments which canno
24、t be calibrated, the deviation tram the nominal value shall be determined by comparison with calibra- 4.8 Residual magnetism tion standards and shall be taken into consideration tor all measurements. Residual magnetism in the basis metal affects measurements made by instruments which employ a statio
25、nary magnetic fjeld. During use, the calibration of the instrument shall be checked Its influence on measurements made by reluctance instruments at frequent intervals. Appropriate attention shall be given to the . employing an alternating magnetic fjeld is much smaller factors listed in clause 4 and
26、 to the procedures specified in (see 6.7). clause 6. 4.9 Magnetic fjelds 5.2 Calibration standards Strang magnetic fjelds, such as those produced by various types of electrical equipment, can seriously interfere with the Callbatlon sta.ndards of umform thlckness are avallable elther operation of ins
27、truments which employ a stationary magnetic as shlms or falls, or as coated standards. fjeld (see 6.7). 5,2.1 Calibration foils 4.10 Foreign particles NOTE -In this sub-clause, the ward “foil“ is used to imply a non- Thbf th.tthtkh.Imagnetic metallic or non-metallic foil or shim. e pro es 0 eins rum
28、en s ave 0 ma e p yslca contact with the test surface because these instruments are sensitive to Bfhd.ff. If.df. 1f. t. Ithtt.t.ttbtwthecause 0 tel ICU ty 0 ensurlng a equate contact, 01 s are orelgn ma erla a preven s In Ima e Gon act e een e . bdthrfftht.Thb.hIdbnot generally recommended tor the c
29、allbratlon of Instruments pro e an e su ace 0 e coa Ing. e pro e tlp s ou e.hkdfII .uslng the magnetlc attractlon prlnclple, but they are sultable tor c ec e or c ean Iness. . ddh. use In same clrcumstances provl etat necessary precautlons are taken. They can normally be used tor the calibration of
30、4.11 Conductivity of coating other types of instruments. . So me magnetic instruments work at frequencies between 200 Foils are advantageous tor ca libration on curved surfaces and and 2000Hz. At these frequencies, eddy currents produced in are more readily available than coated standards. thick, hi
31、ghly conductive coatings may interfere with the reading. To prevent measurement errors, it is necessary to ensure that intimate contact is established between foil and basis metal. 4.12 Probe pressure Resilient foils should be avoided, if possible. The poles of the test probe have to be applied at a
32、 constant but Calibration foils are subject to indentation and shall, therefore, sufficiently high pressure, such that no deformation of the be replaced frequently. coating occurs, even if the coating material is soft. Alternative- Iy, soft coatings may be covered with foils, and the thickness of 5.
33、2.2 Coated standards the foils subtracted tram the test results. Such considerations are also necessary if measuring the thickness of phosphate Coated standards consist of coatings of known, uniform coatings. thickness permanently bonded to a basis metal. 4.13 Probe orientation 53Vf . .erl Icatlon T
34、he readings of instruments using the magnetic attraction prin- ciple may be affected by the orientation of the magnet in rela- 5,3,1 The surface roughness and magnetic properties of the tion to the fjeld of gravity of the earth. Thus, the operation of basis metal of the calibration standards shall b
35、e similar to those 2 ISO 2178-1982 (E) of the test specimen. To confirm their suitability, a comparison 6.5 Number of readings of the readings obtained tram the basis metal of the uncoated calibration standard and that of the uncoated test specimen is Because of normal instrument variability, it is
36、necessary to take recommended“ .several readings in each measuring area (see also ISO 2()64). Local variations in coating thickness mayaiso require that a number of measurements be made in the reference area; this 5.3.2 In same Gases, the calibration of the instrument has to applies particularly if
37、the surface is rough. be checked by rotating the probe through increments of 9() (see 4.7 and 4.8). Instruments of the attractive force type are sensitive to vibra- tions and readings that are obviously tao high shall be 5.3.3 The thickness of the basis metal of the test specimen rejected. and of th
38、e calibration standard has to be the same, if the critical thickness, defined in 4“3, is not exceeded. 6.6 Direction of mechanical working It is often possible to back up the basis metal of the calibration If thed“ lrect “ lon of mhan “ lc Ik“hdfft.“ “ “ “ ec a war Ing as a pronounce e ec standard o
39、r of the test speclmen wlth a sufflclent thlckness of on the reading measurementsOn te tec “ hI1bd“ “IIkhd“ “ddfhb“ , s sp Imenss a ema e slml ar meta to ma e t e rea Ings In epen ent 0 t e asls W“lththeprobe.In th “tt“thtd d“ Ih“ke same arien a Ion as a use urlng meta t IC ness. lOb“If h .“ “ “bikf
40、. ca I ration. t IS IS Impossl e, ma e our measurements In the same measuring area by rotating the probe through increments 5.3.4 If the curvature of the coating to be measured is such as of 9()“ .to preclude calibration on a flat surface, the curvature of the coated standard, or of the substrate on
41、 which the calibration 6.7 Residual magnetism foil is placed, shall be the same as that of the test specimen. If residual magnetism is present in the basis metal, it is necessary, if using a two-pole instrument employing a sta- tionary magnetic fjeld, to make measurements in two orienta- 6 Procedure
42、 tions differing by 180. 6.1 General It ay be necessary to demagnetize the test specimen to obtain valid results. Operate each instrument in accordance with the manufaturer“s instructions, giving appropriate attention to the 6.8 Surface cleanliness factors IIsted In clause 4. .Before making measurem
43、ents, remove any foreign matter, Chec the callratlon ?f the Instr“umen (see cluse 5) at the such as dirt, grease and corrosion products, tram the surface, test slte, each time the Instrument IS put Into service, and at fre- .th t.t “t“ IWhk“ “ “ WI ou removlng any coa Ing ma erla “ en ma Ing quent I
44、ntervals durlng use, to ensure proper performance. t“ dhav “ “ .bl defetthatmeasuremen s, avol any areas Ing VISI e c s are T11“ .h1Ibbdifficult to remove, such as welding or soldering flux, acid he fo owlng precautlons s a e 0 served. td“d spo s, ross, or OXI e“ .6.2 Basis metal thickness 6.9 Lead
45、coatings Check whether the basis metal thickness exceeds the critical If using instruments of the attractive force type, lead coatings thickness. If not, either use the back-up method described in may stick to the magnet. The application of a very thin film 5.3“3 or ensure that the calibration has b
46、een made on a calibra- of oil will generally improve the reproducibility of the tion standard having the same thickness and magnetic proper- measurements, but excess oil shall be wiped off so that the sur- ties as the test specimen. face is virtually dry when measurements are taken with a pull- off
47、type gauge“ Oil shall not be used on coatings other than lead. 6.3 Edge effects 00 not make measurements in the proximity of a discontinuity, 6.10 Techniques such as an edge, hole, inside corner, of a test specimen, unless the validity of the calibration tor such measurements has been The results ob
48、tained may depend on the technique of the demonstrated. operator. For example, the pressure applied to a probe, or the rate of applying a balancing force to a magnet, will vary tram one individual to another. Such effects can be reduced or 6.4 Curvature minimized either by having the instrument cali
49、brated by the same operator who will make the measurement, or by using 00 not make measurements on a curved surface of a test constant pressure probes. In appropriate Gases when a cons- specimen, unless the validity of the calibration tor such tant pressure probe is not being used, the use of a measuring measurements has been demonstrated. stand is strongly recommended. 3 .:C.J; ISO 2178-1982 (E) I - 6.11 Positioning of the probe horizontal or upside-down position, it shall be calibrated separately tor that position if the measuring system is not sup- The