GB/T 31554-2015 English PDF (GBT31554-2015)

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GB/T 31554-2015: Non-magnetic metallic coatings on metallic and non-metallic basis materials -- Measurement of coating thickness -- Phase-sensitive eddy-current method
GB/T 31554-2015
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.220.40
A 29
GB/T 31554-2015 / ISO 21968.2005
Non-magnetic metallic coatings on metallic and non-
metallic basis materials - Measurement of coating
thickness - Phase-sensitive eddy-current method
(ISO 21968.2005, IDT)
ISSUED ON. MAY 15, 2015
IMPLEMENTED ON. JANUARY 1, 2016
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principle ... 4
3 Equipment ... 5
4 Sampling ... 5
5 Factors affecting measurement accuracy ... 5
6 Procedure ... 8
7 Expression of results ... 11
8 Measurement uncertainty ... 11
9 Test report ... 11
Annex A (informative) Eddy-current generation in a metallic conductor ... 13
Annex B (normative) Test for edge effect ... 16
Bibliography ... 18
Foreword
This Standard is drafted according to the rules given in GB/T 1.1-2009.
This Standard uses the translation method to equivalently adopt ISO 21968.2005
“Non-magnetic metallic coatings on metallic and non-metallic basis materials -
Measurement of coating thickness - Phase-sensitive eddy-current method” (English
version).
For easy use, this Standard has the following editorial modifications.
- DELETE the foreword of the International Standard;
- ADD the foreword of China’s national standard;
- The international standards in the standard text and the bibliography are replaced
by identical China’s national standards.
This Standard is proposed by China Machinery Industry Federation.
This Standard shall be under the jurisdiction of National Technical Committee on
Metallic and Nonmetallic Coatings of Standardization Administration of China (SAC/TC
57).
Drafting organizations of this Standard. Guangdong Entry-Exit Inspection and
Quarantine Bureau, Chongqing Institute of Measurement and Quality Testing, Wuhan
Material Protection Institute, Wuhan Kangjie Technology Co., Ltd., Standardization
Research and Development Center of Nanhai District, Dongguan Yian Technology Co.,
Ltd.
Main drafters of this Standard. Zhang Zhenkun, Zhou Qi, Jia Jianxin, Li Xiaomin, Si
Nianpeng, Yu Peng, Gao Zhengyuan, Yu Hui, Hong Fangze and Li Weirong.
Non-magnetic metallic coatings on metallic and non-
metallic basis materials - Measurement of coating
thickness - Phase-sensitive eddy-current method
1 Scope
This Standard describes a method of using phase-sensitive eddy-current instruments
for nondestructive measurements of the thickness of non-magnetic metallic coatings
on metallic and non-metallic basis materials, such as.
a) zinc, cadmium, copper, tin or chromium on steel;
b) copper or silver on composite materials.
The phase-sensitive method can be applied without thickness error to smaller surface
areas and to stronger surface curvatures than the amplitude-sensitive eddy-current
method described in GB/T 4957, and is less affected by the magnetic properties of the
basis material. However, the phase-sensitive method is more affected by the electrical
properties of the coating materials.
When measuring metallic coatings on metallic basis materials, the product of
conductivity and permeability (σ, μ) of one of the materials should be at least a factor
of 1.5 times the product of conductivity and permeability for the other material. Non-
ferromagnetic materials have a relative permeability of 1.
2 Principle
An eddy-current probe (or integrated probe/instrument) is placed on (or near) the
surface of the coating(s) to be measured, and the thickness is read from the
instrument's readout.
For each instrument, there is a maximum measurable thickness of the coating.
Since this thickness range depends on both the applied frequency of the probe system
and the electrical properties of the coating, the maximum thickness should be
determined experimentally, unless otherwise specified by the manufacturer.
An explanation of eddy-current generation and the calculation of the maximum
measurable coating thickness, dmax is given in Annex A.