GB/T 20017-2005: Metallic and other inorganic coatings -- Measurement of mass per unit area -- Review of gravimetric and chemical analysis methods

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Scope

1.1 General
This Standard outlines general methods for determining the average surface
density over a measured area of anodic oxide or of a coating deposited
autocatalytically, mechanically, by chemical conversion, by electrodeposition,
by hot dip galvanizing and by vacuum using gravimetric and other chemical
analysis procedures that have attained some degree of standardization.
A variety of procedures are described and include:
- gravimetric procedures for chemical or electrochemical dissolution of the
coating or the substrate to determine the coating surface density;
- analytical procedures that utilize dissolution of the coating for photometric
or volumetric determination of the coating surface density;
- non-destructive instrumental physical analysis of the coating to determine
the surface density.
With the exception of the gravimetric method described in GB/T 9792, this
Standard does not give the measurement uncertainties of the methods cited.
1.2 Sources
The stripping methods cited in annex A are described in specifications in the
open literature or have been used routinely by at least one laboratory.
1.3 Restrictions
The procedures described can be used for many coating-substrate
combinations. They cannot be used where neither the coating nor substrate
material can be completely removed, one from the other by chemical or physical
means and there is a constituent common to both that is not readily separated
(e.g. nickel phosphorus alloy on nickel).
Note: The measurement of very thin coatings on very small pieces can result in a reduction
in accuracy and a lack of repeatability. Several measurements using a combination
of different procedures on similar samples might overcome this situation.
1.4 Limitations
In principle, the gravimetric procedures can be used to measure very thin
coatings or to measure coatings over small areas, but not thin coatings over
small areas. The limits depend on the required accuracy; e.g., 2.5 mg/cm2 of
coating might require 1 cm2, but 0.1 mg/cm2 of coating would require 25 cm2 to
obtain 2.5 mg of coating. These limitations do not apply to the chemical analysis
methods.
The gravimetric method does not indicate the presence of bare spots or sites
with thicknesses lower than the specified minimum in the measuring areas. In
addition, the single value obtained from each measuring area is the mean
thickness of that area. There can be no further mathematical analysis of this
single value, for example, for statistical process control purposes.

Basic Data

Standard ID	GB/T 20017-2005 (GB/T20017-2005)
Description (Translated English)	Metallic and other inorganic coatings. Measurement of mass per unit area. Review of gravimetric and chemical analysis methods
Sector / Industry	National Standard (Recommended)
Classification of Chinese Standard	A29
Classification of International Standard	25.220.01
Word Count Estimation	16,176
Date of Issue	2005-10-12
Date of Implementation	2006-04-01
Adopted Standard	ISO 10111-2000, IDT
Regulation (derived from)	Announcement of Newly Approved National Standards 2006 No. 1 (No. 88 overall)
Issuing agency(ies)	General Administration of Quality Supervision, Inspection and Quarantine of the People Republic of China, China National Standardization Administration Committee
Summary	This standard outlines have been standardized to some extent the weight of the law and other chemical analysis method for the determination or self- catalytic anodic oxide film deposited layer, mechanical sediment, chemical conversion coating, electrodeposition layer, hot-dip galvanized layer and the average surface density of vacuum deposited layer the general method.