GB/T 4957-2003 English PDF (GBT4957-2003)

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GB/T 4957-2003: Non-conductive coatings on non-magnetic basis metals -- Measurement of coating thickness -- Eddy current
GB/T 4957-2003
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.220.40
A 29
GB/T 4957-2003 / ISO 2360:1982
Replacing GB/T 4957-1985
Non-conductive coatings on non-magnetic basis
metals - Measurement of coating thickness - Eddy
current
(ISO 2360:1982, IDT)
ISSUED ON: OCTOBER 29, 2003
IMPLEMENTED ON: MAY 01, 2004
Issued by: General Administration of Quality Supervision, Inspection
and Quarantine of the People's Republic of China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Principle ... 4 
4 Factors affecting measurement certainty ... 5 
5 Calibration of instruments ... 7 
6 Measurement procedure ... 8 
7 Accuracy requirements ... 9 
Foreword
This Standard identically adopts ISO 2360:1982 “Non-conductive coating on
non-magnetic basis metals - Measurement of coating thickness - Eddy current
method” (English edition).
This Standard replaces GB/T 4957-1985 “Non-conductive coatings on non-
magnetic metal substrates - Measurement of coating thickness - Eddy current
method”.
Based on ISO 2360:1982, this Standard made the following editorial
modifications:
a) used “this Standard” to replace “this International standard”;
b) deleted the foreword of ISO 2360:1982;
c) used national standards that adopt international standards as references;
d) added normative references.
This Standard was proposed by China Machinery Industry Federation.
This Standard shall be under the jurisdiction of National Technical Committee
on Metal and Non-metal Coatings of Standardization Administration of China.
Main drafting organization of this Standard: Wuhan Institute of Material
Protection.
The drafting organization of this Standard: Zhejiang Yueqing Xinfeng Enterprise
Co., Ltd.
Main drafters of this Standard: Yu Hui, Zhong Lichang, Feng Yongchun, Jia
Jianxin, Zheng Xiulin.
Version of standard substituted by this Standard is:
- GB/T 4957-1985.
Non-conductive coatings on non-magnetic basis
metals - Measurement of coating thickness - Eddy
current
1 Scope
This Standard describes a method for non-destructive measurements of the
thickness of nonconductive coatings on non-magnetic, electrically conductive
(generally metallic) basis materials, using amplitude-sensitive eddy current
instruments.
The method is particularly applicable to measurements of the thickness of most
oxide coatings produced by anodizing, but is not applicable to all conversion
coatings, some of which are too thin to be measured by this method (see Clause
7).
Although theoretically, the method can be used for measurements of the
thickness of coatings on magnetic basis materials, its use for this application is
not recommended. In such cases, the magnetic method specified in GB/T 4956
should be used.
2 Normative references
The provisions in following documents become the provisions of this Standard
through reference in this Standard. For dated references, the subsequent
amendments (excluding corrigendum) or revisions do not apply to this Standard,
however, parties who reach an agreement based on this Standard are
encouraged to study if the latest versions of these documents are applicable.
For undated references, the latest edition of the referenced document applies.
GB/T 4956, Non-magnetic coatings on magnetic substrates - Measurement
of coating thickness - Magnetic method (ISO2178:1982, IDT)
3 Principle
An eddy current probe (or integrated probe/instrument) is placed on the surface
of the coating(s) to be measured, and the thickness is read from the
instrument's readout.