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AS 3894.1—20021

Australian StandardTM

Site testing of protective coatings

Method 1: Non-conductive coatings—Continuitytesting—High voltage (brush) method

PREFACEThis Standard was prepared by the Australian members of the Joint StandardsAustralia/Standards New Zealand Committee CH-003, Paints and Related Materials, tosupersede AS 3894.1—1991. After consultation with stakeholders in both countries,Standards Australia/Standards New Zealand decided to develop this Standards as anAustralian Standard rather than an Australian/New Zealand Standard.

The Standard was originally requested by the Queensland and New South Wales pro-fessional associations concerned with blast cleaning and the protection of heavy-dutystructures.

This test method is intended to locate accurately defects, which may subsequently berepaired by appropriate procedures, prior to the item being placed into service.

This Standard is part of a series of Standards that provide test methods for inspectors andtechnical staff involved in the conduct of continuity testing and the assessment of results.As products tested are generally expected to exhibit long life without maintenance, and areoften difficult or costly to assess once installed, it is essential that sound inspectionmethods are used and accurate test results are obtained before product installation can becommenced.

This Standard has drawn on literature issued by many professional bodies and instrumentmanufacturers, and acknowledgement is made of the assistance received. Source documentsinclude the following:

AMERICAN SOCIETY FOR TESTING AND MATERIALS. ASTM G62-87 Test methodsfor holiday detection in pipeline coatings. Philadelphia: ASTM, 1984.

NATIONAL ASSOCIATION OF CORROSION ENGINEERS. NACE RP 0188-88Discontinuity (holiday) testing of protective coatings. Houston: NACE, 1988.

STEEL STRUCTURE PAINTING COUNCIL. Steel structures painting manual. Pittsburgh:SSPC, June 1983, vol. 1, pp 202-205.

BARTLETT, D.J. Cost effective coating inspection. Corrosion Australasia. April 1983,pp 8-12.

The terms ‘normative’ and ‘informative’ have been used in this Standard to define theapplication of the appendix to which they apply. A ‘normative’ appendix is an integral partof a Standard, whereas an ‘informative’ appendix is only for information and guidance.

AS 3894.1

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AS 3894.1—2002 2

CONTENTS

Page

FOREWORD ................................................................................................................... 31 SCOPE........................................................................................................................ 32 APPLICATION........................................................................................................... 33 REFERENCED DOCUMENTS.................................................................................. 44 DEFINITIONS............................................................................................................ 45 PRINCIPLE ................................................................................................................ 46 MATERIALS.............................................................................................................. 57 APPARATUS ............................................................................................................. 58 SAMPLE AND TEST PREPARATION ..................................................................... 79 PROCEDURE ............................................................................................................. 8

10 REPORT ..................................................................................................................... 8

APPENDICESA SAFE PRACTICE IN THE OPERATION OF HIGH VOLTAGE TESTERS............ 10B PROCEDURES FOR CHECKING PROPER OPERATION OF HIGH

VOLTAGE TESTERS ............................................................................................... 13C PROCEDURE FOR CALIBRATION OF HIGH VOLTAGE TESTERS................... 12D VOLTAGE FOR TESTING SPECIFIED FILM THICKNESSES OF

VARIOUS COATING PRODUCTS.......................................................................... 16E SAMPLE REPORT FORM FOR CONTINUITY TESTING ..................................... 20

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FOREWORDTesting of the electrical properties of a continuous protective coating on metal may becarried out by various procedures, which yield differing results not related to the durabilityof the coating. Measurement of current flowing under the stress of high voltages provides ameasure of the ohmic or volume resistivity. Application of alternating voltage produces acurrent related to the dielectric constant of the coating material. Measurement of currentflow when the film is wet with conducting salts will provide a value for anothercharacteristic.

The purpose of this Method is to produce electrical breakdown in a discontinuity, whichexists between the substrate and the exploring electrode, wherever the electrode passes overa pinhole or defect in the coating. When films have been deposited from solvent-bornecoatings, such pinholes in newly applied coatings may contain a significant vapour pressureover a prolonged period. As the available literature does not establish the degree to whichthe dielectric strength of air is altered by the solvent vapour content during high voltagetesting, the committee carried out cooperative testing to address the behaviour ofthermoplastics films. This work resulted in the empirical values adopted in Appendix D.

Although the coatings being considered here are applied to the metal substrate in liquidform, they may not necessarily be homogeneous or isotropic in nature, which may imposelimitations on the suitability of certain types of instrument for this test method. In addition,a specified delay may be required between the application of the coating and performanceof the test. The design of the fabricated object may render this test unsuitable.

The rectification of discontinuities found by the use of this method should prolong the lifeof a coating.

METHOD1 SCOPE

This Standard provides a practical test method for the on-site determination of the presenceof pinholes, holidays, cracks and other discontinuities that penetrate to the substrate, in anon-conductive, protective coating of at least 150 µm thickness (see Note) on a conductivesubstrate, using the high voltage or ‘brush’ method.

NOTE: Where coatings are less than 150 µm thick, an alternative method such as the low voltagewet sponge method should be used.

This Standard is applicable to site testing of coated metal items of equipment or structureswhich may be subjected to long-term burial or immersion, such as structural steel,pipelines, storage vessels, bridges and mobile/transportable containers. The method isconfined to testing instruments that can provide a minimum voltage of 500 V. The Standardis not intended to apply to coating types incorporating components that conduct an electriccurrent, such as zinc dust and aluminium flakes.

The voltages recommended in this Standard are intended to be applied under conditions ofnormal atmospheric pressure and temperature.

2 APPLICATION

Although it may be used in the laboratory for inspecting panels and relatively small testitems, the Method is intended for use in the field (see also Clause 8).

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WARNING: OWING TO THE POSSIBILITY OF THE TEST INSTRUMENTSINTERFERING WITH ELECTRICAL DEVICES SENSITIVE TO MAGNETICAND ELECTRIC FIELDS, IT SHOULD BE ENSURED THAT OPERATORSHAVING PACEMAKERS OR OTHER BIO-ELECTRICAL DEVICES DO NOTUSE THIS METHOD. REFER TO AS 2243.7 FOR GENERAL SAFE HANDLINGOF ELECTRICAL DEVICES AND TO APPENDIX A FOR SAFE PRACTICESWHEN CONDUCTING HIGH VOLTAGE TESTING.

3 REFERENCED DOCUMENTS

The following documents are referred to in this Standard:AS2886 Voltage measurement—Sphere-gap method (one sphere earthed)AS/NZS1580 Paints and related materials—Methods of test1580.101.5 Method 101.5: Conditions of test, temperature and humidity control2243 Safety in laboratories2243.7 Part 7: Electrical aspects2310 Glossary of paint and painting terms3894 Site testing of protective coatings3894.7 Part 7: Determination of surface temperature

4 DEFINITIONS

For the purpose of this Standard, the definitions of AS/NZS 2310 and those below apply.

4.1 Coating

A material, applied to a surface at a specified film thickness, that is intended to protect thesurface from corrosive elements or conditions such as moisture, gases, and abrasion bywind-blown or waterborne particles. A coating may also be required to insulate thesubstrate from temperature extremes.

4.2 Continuity

The quality of a coating that determines its freedom from those defects that increase itselectrical conductivity.

4.3 Defect

A detectable weakness or discontinuity in a coating, which causes its ability to protect thesubstrate from corrosion to be suspect during the normal service life.

4.4 Holiday

A localized defect, characterized by a coating having areas of insufficient thickness,including the point where parts of the substrate may be uncoated.

4.5 Pinhole

A minute hole in a dry coating, which forms during the application and drying of thecoating material.

5 PRINCIPLE

The electrode of a high voltage tester is passed over the surface to be tested at a prescribedrate. The location of any defect, as indicated by the instrument’s response, is highlightedwith a specified marker on the surface of the test area.

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6 MATERIALS

6.1 Cleaning solutions/agents

Alkaline oil emulsifiers in solution, or solvent recommended for this purpose by themanufacturer of the coating.

For routine testing, potable water shall be used throughout the test (e.g. for preparingsolutions or rinsing operations). The water shall be free of any levels of impurities thatwould affect the outcome of the test.

For referee testing, the water shall have a conductivity ≤50 µS.

6.2 Marker

A suitable marker, such as chalk or a spirit pen, used to mark the position of defects.Crayon or grease-based materials shall not be used.

7 APPARATUS

7.1 High voltage tester

7.1.1 General

The high voltage test unit shall be of robust construction. The essential components of thehigh voltage tester shall comply with the requirements of Clauses 7.1.2 to 7.1.7.

The high voltage tester shall be calibrated in accordance with Appendix B.NOTE: Guidance on checking high voltage testers is given in Appendix C.

7.1.2 Power supply

The power supply shall deliver d.c. voltage, either continuous or pulsed, suitable for thecoating to be tested, which may be adjusted in increments as described in Clause 7.1.4(c),and is stable to within ±2% at the power output points and display meter for the duration ofthe test. The output voltage shall be measured under load conditions.

If the source of power is a battery and there is doubt about battery condition, a fullycharged battery should be installed prior to commencing the test.

7.1.3 Detector

The detector unit is usually located in a common housing with the power supply (seeClause 7.1.2), and is designed to indicate the flow of current, in the form of a spark passingfrom the electrode to the substrate, through a defect (pinhole, holiday or reduced filmthickness) in the coating on the test item. The detector exhibits the current flow visually oraudibly by means of a pointer, a spark, a light-emitting diode (LED) or a loudspeaker(which may be in the form of a headphone). To avoid false indications, the sensitivity of thealarm may be altered to allow use on coatings of various generic types and under differingtest conditions.

7.1.4 Electrical output

The electrical output of the combined unit described in Clause 7.1.2 shall have thefollowing features:

(a) Detector instruments used to test coating systems of thickness 500 µm or less shall beprovided with either—

(i) an unpulsed, constant d.c. voltage output, containing not more than 5% of thepeak voltage present as a ripple content; or

(ii) a pulsed voltage output that is substantially undirectional, provided it has beendemonstrated that such a waveform does not result in damage to the coating.

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(b) Instruments used on coating systems exceeding a thickness of 500 µm shall beprovided with an unpulsed d.c. (see Item (a) above) or a pulsed d.c. voltage output.The voltage indicator shall correspond with the peak value of the output, and thepulse frequency shall not be less than 30 Hz for pulsed instruments.

(c) The output voltage of the detector shall be adjustable, in increments appropriate to thenominal film thickness, as follows—:

(i) Up to 500 µm ………..……………………. in increments not exceeding 100 V.

(ii) Greater than 500 µm ……………………… in increments not exceeding 500 V.

(d) The maximum operating current shall not exceed the safety limits determined by therelevant regulatory bodies.

7.1.5 Indicators

The combined unit described in Clauses 7.1.2 and 7.1.3 shall have the following additionalfeatures:

(a) Voltage indicator A visual display that indicates the nominal voltage at the probe tiprelative to ground, accurate to within ±5% of the true value. The detector shall befitted with a visual display indicating the nominal voltage at the probe tip relative tothe ground, to the nearest 10 V.

(b) Battery condition indicator Battery-operated detector fitted with a visual or audibletransducer that indicates the suitability or condition of the battery for subsequent use.

(c) Alarm-discontinuity indicator A visual and audible alarm system to indicate thepresence of the defect in the test coating. The sensitivity of the alarm should beadjustable and a visible indicator may be fitted.

7.1.6 Electrodes

For routine purposes, and depending upon the item to be tested, the electrode or probe shallbe in the form of one of the following:

(a) Brush-type electrode Consisting of a continuous, multi-stranded linear brush (seeNote) of design such that, when passed over the test surface in the recommendedmanner, the bristle density and the stiffness of the fibre will ensure that the electrodeprovides an unbroken sweep over the test area, that is, all points of the surface in thepath of the brush will be electrically swept. The length of wire bristle shall beappropriate to the brush flexibility, so that the tip of the bristle maintains intimatecontact with the test coating during normal passage of the brush.

(b) Rolling, brush or coil spring electrode Having dimensions that permit it to fitclosely over the test item, so that the electrode makes and maintains electrical contactand traverses all points on the coating surface. The spring shall be so designed that,when in service, each individual coil is in intimate contact with adjacent coils.

(c) Conductive strip Of carbon-impregnated rubber, or flexible plastics.

For referee purposes, only the brush-type electrode shall be used.NOTES: 1 Where the small scale of an item justifies use of a flexible fan brush, the separation of the

bristle tips at the test surface during the test may be up to 1 mm. When using such a fanbrush, repeated passes may be needed to ensure that all points on the test surface aretraversed.

2 The coil spring electrode should be manufactured using square-section wire.

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7.1.7 Ground wire

To be electrically connected to the substrate of the coated test item and to the testingapparatus.

7.2 Thermometer

To measure the surface temperature of the test area to an accuracy of ±1°C.

7.3 Dewpoint apparatus

Capable of determining the dew point of the air in the vicinity of the test surface inaccordance with AS/NZS 3894.7 to an accuracy of ±1°C.

NOTE: This apparatus is recommended for the field, to assist in determining the suitability ofconditions for testing.

7.4 Certified voltmeter

To check the voltage output of the electrode. It shall have resolution of 10 V and beaccurate to within 1% of the true value. For pulsed voltages, the voltmeter shall measurepeak voltage output.

8 SAMPLE AND TEST PREPARATION

8.1 Testing conditions

8.1.1 Field testing

For field testing, the temperature of the test surface should be at least 3°C above thedewpoint (see Clause 7.3 for relevant apparatus).

The test surface should be dry with an absence of condensation.

8.1.2 Laboratory testing

When conducting tests in a laboratory environment, the test conditions shall be inaccordance with AS/NZS 1580.101.5.

8.2 Preliminary inspection of test item

Prior to commencing testing, the item to be tested shall be inspected and any visible defectsshall be clearly highlighted with the marker specified in Clause 6.2. The immediate areacontaining these defects shall not be subjected to high voltage testing until the defects havebeen repaired. Note should also be taken of sharp edges, exposed protrusions (e.g., nuts,bolts), irregular weld deposits and any other features that may cause difficulties whenconducting a full and proper instrumental assessment of the coating.

8.3 Preparation of test area

Prior to the commencement of continuity testing, the test area shall be prepared as follows:(a) Ensure that the application and curing instructions of the manufacturer or the supplier

of the coating material have been followed, that the coating is cured and of thespecified dry film thickness.

NOTES: 1 Preformed sheeting, intended to be applied as a coating to the substrate, is supplied in

pre-cured form. Hence, products coated with this material should not require a check forstate-of-cure.

2 The dry film thickness of the coating should be measured to an accuracy of ±10% using anappropriate non-destructive method.

(b) Inspect the test area for the presence of any foreign deposits (including grease) and,where necessary, remove such matter using an appropriate method. Cleaningsolutions/agents shall comply with the requirements of Clause 6.1.

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9 PROCEDURE

The procedure shall be as follows:

(a) Ensure that the high voltage testing equipment has been calibrated recently, inaccordance with Appendix B.

(b) Determine the voltage appropriate for evaluation of the coating and the dry filmthickness, in accordance with Appendix D.

(c) Adjust the voltage of the test instrument to the appropriate setting.NOTE: Guidance on checking the operation of the instrument is given in Appendix C.

(d) After thoroughly cleaning an exposed (uncoated) portion of the substrate, secure anearth connection to the substrate using the earth return cable and clamp supplied withthe instrument. A bared section of this earth connection shall be within easy reach ofthe operator throughout the test (see Note 2 to Step (e)).

(e) Pass the electrode over the test area, at a rate of not greater than 0.3 m/s maintainingcontact between the electrode and the test area, using an appropriate motion (seeNote 1).CAUTION: DO NOT ALLOW THE ELECTRODE TO BECOME STATIONARYRELATIVE TO THE TEST SURFACE, OR COATING DAMAGE MAY RESULT.NOTES: 1 For brush electrodes, a sweeping or ‘brush-painting’ action is suitable. For coils and

roller-mounted brushes, a continuous linear pass is recommended.2 It is important that a regular check be made on the satisfactory operation of the spark or

alarm by touching the probe against an earth contact at regular intervals, and when theearth is relocated.

3 The instrument settings should be checked at least once each 20 min interval.

(f) When the instrument indicates a defect, by the audible or visible signal, determine theexact location of the defect (do not hold electrode stationary against surface), andclearly identify it on the test surface with the marker (see Clause 6.2).

(g) Continue testing until the whole of the designated area has been assessed.

(h) Count and record the number of defects found, expressing them as ‘defects per item’or ‘defects per unit area tested’, e.g. defects per square metre.

10 REPORT

The report shall include the following information:

(a) Name of testing laboratory/authority/inspector.

(b) Date of the test and report number.

(c) Identification and description of the item tested and its coating, including shape,substrate material, coating type and specified film thickness.

(d) A description of the location where the test was conducted, the project identificationand the test conditions.

(e) Description of the test equipment used and calibration details (see Appendix B).

(f) Film thickness measurements and the method used for their determination.

(g) Voltage selected to conduct the continuity test and calibration details.

(h) Results of the test expressed as defects per item, or defects per unit area tested.

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(i) Any other information or observation to assist in the correct interpretation of theresults (for example, cleaning water purity, surface conditions, any apparent factorsthat may have contributed to the formation of defects, inadequate curing).

(j) Reference to this Australian/New Zealand Standard, i.e. AS/NZS 3894.1.

(k) Any deviations from this test method.NOTE: Appendix E provides a sample test report form.

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APPENDIX A

SAFE PRACTICE IN THE OPERATION OF HIGH VOLTAGE TESTERS

(Informative)

A1 SCOPE

This Appendix provides information on the safe practices to be observed when operatinghigh voltage conductivity testing equipment.

WARNING: HIGH VOLTAGE TESTERS MAY GENERATE VOLTAGES INEXCESS OF 40 000 V.

A2 OPERATORS

All high voltage test equipment should be operated by responsible, trained and authorizedpersonnel only. Trainees should understand the basic principles governing the operation ofthe equipment prior to any physical training being undertaken

NOTE: It is desirable that operators hold, or work under the supervision of a person that holds, arecognized coating inspection certificate issue by the Australian Corrosion Association or theNational Association of Corrosion Engineers.

Personnel who require bio-electrical devices such as pacemakers should not operate highvoltage testing equipment.

A3 TESTING LOCATION

Testing should be carried out well clear of personnel not involved in the testing procedure,or in such a position that the receipt by an individual of an electric shock would not cause arelated accident. For example, tests should not be carried out close to moving or rotatingmachinery, or in an unstable position where the operator could fall and be injured.

Testing should preferably be undertaken at floor level. Where elevated testing is necessary,scaffolding should be provided. The scaffolding should be fitted with handrails, kickboards,and should meet the requirements laid down by the appropriate regulatory authority.

A4 ENVIRONMENTAL HAZARDS

A4.1 Hazardous areas

Prior to testing, the operator should ensure that the area is free of flammable vapours anddusts. The area should be checked by an approved flammability testing instrument, and theplant or safety officer should be consulted before carrying out testing.

A4.2 Ventilation

Ventilation should be provided where testing occurs in enclosed spaces or areas.

A4.3 Paints

Containers of paint thinners or other flammable materials should be removed and storedaway from a testing area.

A5 USE OF TESTING EQUIPMENT

A5.1 Instructions

The instructions of the manufacturer or equipment supplier should be available to theoperator.

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A5.2 Routine check

The operator should check the equipment before use, and specifically note the following:

(a) An absence of cracking or other damage to the case, connectors, insulation orelectrical leads.

(b) Whether connectors are insulated and not bare.

A5.3 Warning signs

Appropriate warning signs, referring to electrical and explosive hazards, should bedisplayed in the test area.

NOTE: Local regulations should be observed.

A5.4 Protective clothing

Operators should wear insulating gloves when testing at high voltages. Gloves suitable toprotect against the maximum output of the detector.

Appropriate safety footwear should be worn.

A6 EARTHING

To ensure satisfactory operation of the high voltage tester, it is essential that one side of theelectrical circuit, referred to as the ‘earth return’, is connected to the substrate of thecoating being tested.

Where possible, this connection is made by direct metal-to-metal connection of the earthlead to the substrate, e.g. the body of a tank or a pipeline. In certain circumstances, theconnection may be made through the ground (natural soil) upon which the item rests.Although there is a moderately high resistance, sufficient conductivity of this soil does notlower the voltage applied to the intact coating, although it acts to quench the sparkrelatively quickly after detection of a pinhole.

Whenever personnel use high voltage testing instruments inside or upon a metal fabrication,the fabrication is to be firmly connected to the ground to which personnel descend during oron completion of the task. A grounding wire, connected to the test substrate and to aconductive spike driven into the soil to a depth of at least 600 mm, is required.

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APPENDIX B

PROCEDURE FOR CALIBRATION OF HIGH VOLTAGE TESTERS

(Normative)

B1 SCOPE

This Appendix specifies the procedure and frequency of testing for the calibration of highvoltage testers used in the determination of continuity of non-conductive coatings.

B2 PRINCIPLE

The high voltage tester is calibrated, at regular intervals, against a voltmeter that has beencertified by an approved testing laboratory, or in accordance with AS 2886.

B3 CALIBRATION FREQUENCY

At no longer than one month before the intended determination of coating continuity, thehigh voltage tester shall be calibrated with an appropriate voltmeter (see Note) which,within 2 years, has been calibrated in the proposed voltage range by a laboratory certifiedfor that purpose.

If a certified voltmeter is not available, the high voltage tester may be calibrated by thesphere gap method specified in AS 2886.

NOTE: It is assumed that the certified voltmeter has been calibrated to measure either d.c. or peakvoltage, as appropriate to the high voltage tester.

B4 CALIBRATION VOLTAGES

The calibration shall be performed using at least three points that span the voltage scale,viz. at or near the maximum output voltage, halfway between the maximum and theminimum output voltage, and at the minimum output voltage of the instrument.

B5 STABILITY AND PRECISION OF OUTPUT

The voltage output shall be measured when the earth circuit is grounded to a steel substratebearing a pinhole-free non-conducting coating over which the probe is passed.

The voltage output shall be stable in that the measured voltage, on any setting of theinstrument, shall not vary by more than 2% of its original value over a period of continuousoperation of at least 1 h.

B6 INFORMATION TO ACCOMPANY AN INSTRUMENT REQUIRINGCALIBRATION

When an instrument is sent for calibration, it shall be accompanied by a maker’s certificatecertifying the following information:

(a) The type of electrical output (continuous d.c. and pulsed wave forms).

(b) Pulse repetition frequency, if appropriate.

(c) Any ripple frequency and its proportional content if it is 5% or more of the steadyoutput.

Instruments for which a maker’s certificate is unavailable shall be provided with acertificate of examination giving the above information.

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APPENDIX C

PROCEDURES FOR CHECKING PROPER OPERATION OF HIGH VOLTAGETESTERS

(Informative)

C1 SCOPE

This Appendix sets out two methods for checking that the high voltage tester is operatingsatisfactorily in circumstances where a calibrated voltmeter is not available.

C2 PRINCIPLE

The preferred method, Method A, involves the provision and testing of a reference steelpanel or test piece that has been coated carefully at the same time as the work underexamination.

An alternative method, Method B, may be used where a number of insulating sheets, in arange of thicknesses, is available.

NOTE: The operator needs to ensure that the voltage given in Appendix D is adopted for testingthe continuity of the coating, and should not use the voltage set for checking the operation overinsulating shims.

C3 METHODS

C3.1 Method A—Coating on test plate

C3.1.1 Apparatus

A duplicate test plate, coated and cured in the same way as the installed component, isrequired.

C3.1.2 Procedure

The procedure shall be as follows:

(a) Prepare the test area as described in Clause 8 of this Standard.

(b) Make a small hole of nominal diameter 1 mm in the test surface through to thesubstrate, ensuring that no conductive particles are left in the hole.NOTE: Conductive dust or particles can be produced by improper drilling and can seriouslyreduce the non-conductive path between the electrode and substrate in subsequent testing.

(c) Perform Steps (a) to (d) of Clause 9 of this Standard over the punctured area of thetest piece. If the tester is operating satisfactorily, and the voltage correctly set, adischarge will occur as the electrode passes over the hole. If no discharge occurs,even on repeated passes, either—

(i) the dry film thickness at the hole is significantly greater than expected; or

(ii) the apparatus is incorrectly set or is malfunctioning. Check both of these factorsby—

(A) redetermining the dry film thickness in the vicinity of the hole by thereference method; and

(B) carrying out a service of the high voltage tester, including a calibrationcheck.

The problem should be resolved and corrected before proceeding with evaluation ofthis film’s continuity.

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C3.2 Method B—Using insulating shims

C3.2.1 Apparatu

C3.2.1.1 Insulating sheets (see Note)

A set of insulating sheets is required, in a range of thicknesses appropriate to the nominaldry film thickness of the test coating and of minimum dimensions 150 mm × 300 mm. A1 mm diameter hole shall be drilled through the centre of each sheet.

NOTE: Phenolic or other electrical grade thermoset fibre-reinforced sheets (as used in circuitboards) have been found to be very suitable, as these materials are designed to resist melting orcharring by the heat developed during the test.

C3.2.1.2 Steel plate

A flat, light gauge steel plate is required, of nominal dimensions 300 mm × 300 mm, whichhas been cleaned of any oxide or other films that may inhibit production of a spark or theformation of a good earth connection.

C3.2.2 Procedure

The procedure shall be as follows:

(a) Set up the high voltage tester with a sound earth connected to the steel plate.

(b) Select an insulating sheet, of thickness corresponding to that of the appropriate dryfilm thickness, and place it on the steel plate. Ensure that the sheet is clean, flat andin intimate contact with the plate.

(c) Select a test voltage by use of the measured dry film thickness using the followingequation—

FTV √= 250 . . . B3.2.2

where

V = test voltage applied, in volts

T = thickness of insulating sheet, in micrometres

F = coating film rating, F = 1

Alternatively, the test voltage may be determined from Figure B1.

(d) Pass the electrode (probe) over the hole of the sheet but do not insert it into the hole.

(e) If the tester is operating satisfactorily at the voltage selected, a spark will occurindicating the voltage is at least equal to the setting. If no sparking occurs, the tester,including leads, requires servicing.

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FIGURE B1 TEST VOLTAGE FOR INSULATING SHEETS

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APPENDIX D

VOLTAGE FOR TESTING SPECIFIED FILM THICKNESSES OF VARIOUSCOATING PRODUCTS

(Normative)

D1 SCOPE

This Appendix indicates the test voltage appropriate for the detection of discontinuities incoatings, of different generic types and various dry film thicknesses, that penetrate into thesubstrate.

D2 GENERAL

The test voltages are selected in accordance with the following equation:

FTV √=

250 . . . D2

where

V = test voltage applied, in volts

T = specified dry film thickness of cured coating, in micrometres

F = rating of a coating’s generic type and the volume solids content (see Table D1).

Where the actual film thickness exceeds the specified film thickness (T) by 25 %, the testvoltage (V) should be recalculated using the actual thickness of that area.

TABLE D1

DETERMINATION OF THE COATING FILM RATING (F) FROM COATINGTYPE AND VOLUME SOLIDS CONTENT

Generic type of coatingVolume solids

% (V/V)Rating

(F)

Chlorinated rubberVinyl

15 to 39 4

Low-build epoxyTar epoxy

40 to 59 3

High-build epoxyTar epoxy

60 to 79 2

Polyester-vinyl esterSolventless epoxyFusion-bonded epoxy

80 and greater 1

NOTE: Coating materials with a volume solids content of less than 15% are not normally used forthe purposes described in the Scope of this Standard.

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TABLE D2

DETERMINATION OF TEST VOLTAGE (V) FROMTHE DRY FILM THICKNESS (T)

AND COATING MATERIAL RATING (F)

Test voltage, kVNominal dryfilm thickness

µµµµmF = 1 F = 2 F = 3 F = 4

150 3.06 1.53 1.01 0.77

160 3.16 1.58 1.05 0.79170 3.26 1.63 1.09 0.82180 3.35 1.68 1.12 0.84190 3.45 1.72 1.15 0.86200 3.54 1.77 1.18 0.88250 3.96 1.98 1.32 0.99260 4.03 2.02 1.34 1.01300 4.33 2.17 1.44 1.08350 4.68 2.34 1.56 1.17400 5.00 2.50 1.67 1.25450 5.30 2.65 1.77 1.33500 5.60 2.80 1.86 1.40550 5.87 2.94 1.96 1.47600 6.12 3.06 2.04 1.53650 6.37 3.19 2.13 1.60700 6.61 3.31 2.21 *750 6.85 3.42 2.28 *800 7.07 3.54 2.36 *850 7.29 3.64 2.43 *900 7.50 3.75 2.50 *

1000 7.91 3.96 * *1500 9.69 4.84 * *2000 11.18 * * *2500 12.50 * * *3000 13.69 * * *3500 14.79 * * *4000 15.81 * * *

* The coatings corresponding to the appropriate factor are not normally applied at theindicated dry film thickness.

NOTE: The values in the Table apply to—

(a) solvent-based and solvent-free coatings;

(b) the use of both d.c. smooth and pulse detectors (see Clause 7.1.3);

(c) the use of a direct earth connection to the coated substrate; and

(d) the use of an electrode consisting of a brush with fine metallic fibres, such as brass,tufted to ensure complete contact with the coating surface.

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FIGURE D1 TEST VOLTAGES FOR FILMS WITH F1 ANDF2 COATING RATINGS

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FIGURE D2 TEST VOLTAGES FOR FILMS WITH F3 ANDF4 COATING RATINGS

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APPENDIX E

SAMPLE REPORT FORM FOR CONTINUITY TESTING

(Informative)

AS/NZS 3894.1 TEST REPORT

Continuity testing of non-conductive coatings—High voltage method

Project: ............................................................................................................................................................

Contract No.: ...................................................................................................................................................

Name of testing laboratory/authority: ......................................................................................

Date of conduct of test: ..................................... Report number: ..................................................................

Identification/description of test item

Substrate material: ..........................................................................................................................................

Description of workpiece: ...............................................................................................................................

Coating system: ..............................................................................................................................................

Method of coating application and date: ........................................................................................................

Curing conditions (time/temperature): ............................................................................................................

Method of cure: ...............................................................................................................................................

Specified dry film thickness: ...........................................................................................................................

Test procedure

Surface cleaning prior to testing: ....................................................................................................................

Dry film thickness—instrument used: .............................................................................................................

—results (µm): ..................................................................................................................

Dewpoint and surface temperature: ...............................................................................................................

Brand/model of test equipment: .....................................................................................................................

Date of last calibration ....................................................................................................................................

Test voltage selected: .....................................................................................................................................

Test results

Percentage of area tested: .............................................................................................................................

Number of defects detected (per item or m2): ...............................................................................................

Pass To be repaired

Comments, if any, to assist in interpretation of results: .................................................................................

..........................................................................................................................................................................

..........................................................................................................................................................................

Inspector’s name (print): .............................................. Signature: ......................................................

Name of contractor's representative (print): ............................................................................

Signature of contractor's representative: ...............................................................................................

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AS 3894.1—200221

NOTES

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AS 3894.1—2002 22

NOTES

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AS 3894.1—200223

NOTES

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AS 3894.1—2002 24

This Australian Standard was prepared by Committee CH-003, Paints and Related Materials. It was approved on behalf of the Council ofStandards Australia on 29 March 2002 and published on 7 June 2002.

The following are represented on Committee CH-003:

Australian Paint Approval SchemeAustralian Paint Manufacturers FederationAUSTROADSBuilding Research Association of New ZealandInstitution of Professional Engineers New ZealandMaster Painters AustraliaNational Association of Testing Authorities AustraliaNew Zealand Abrasive Blasting AssociationNew Zealand Manufacturers FederationNew Zealand Painting Contractors AssociationSurface Coatings Association AustraliaTelstra CorporationWater Corporation Western Australia

Additional interests participating in the preparation of this Standard:

Australian Institute of Protective CoatingsBlast Cleaning and Coating Association QLDSydney Water Corporation

Keeping Standards up-to-dateStandards are living documents which reflect progress in science, technology and systems. To maintain their currency, all Standards areperiodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. Itis important that readers assure themselves they are using a current Standard, which should include any amendments which may have beenpublished since the Standard was purchased.Detailed information about Standards can be found visiting the Standards Australia web site at www.standards.com.au and looking up therelevant Standard in the on-line catalogue.Alternatively, the printed Catalogue provides information current at 1 January each year, and the monthly magazine, The AustralianStandard, has a full listing of revisions and amendments published each month.We also welcome suggestions for the improvement in our Standards, and especially encourage readers to notify us immediately of anyapparent inaccuracies or ambiguities. Contact us via email at mail@standards.com.au, or write to the Chief Executive, Standards AustraliaInternational Ltd, GPO Box 5420, Sydney, NSW 2001.

Originated AS 3894.1—1991.Second edition 2002.

This Standard was issued in draft form for comment as DR 01385.

COPYRIGHT© Standards Australia International

All rights are reserved. No part of this work may be reproduced or copied in any form or by any means, electronicor mechanical, including photocopying, without the written permission of the publisher.

Published by Standards Australia International LtdGPO Box 5420, Sydney, NSW 2001, Australia

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