GB/T 19355.3-2016 English PDF (GB/T19355.3-2016)

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GB/T 19355.3-2016: Zinc coatings -- Guidelines and recommendations for the protection against corrosion of iron and steel in structures -- Part 3: Sherardizing
GB/T 19355.3-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.220.40
A 29
Partially replacing GB/T 19355-2003
Zinc Coatings - Guidelines and Recommendations for the
Protection Against Corrosion of Iron and Steel in Structures -
Part 3. Sherardizing
(ISO 14713-3.2009, MOD)
ISSUED ON. FEBRUARY 24, 2016
IMPLEMENTED ON. SEPTEMBER 1, 2016
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration Committee of the People’s
Republic of China.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative References ... 5 
3 Terms and Definitions ... 6 
4 Sherardizing Design ... 6 
5 Storage and Transportation ... 9 
6 The Influence of Workpieces’ State on Sherardizing Quality... 10 
7 The Influence of Sherardizing on Workpieces ... 12 
8 Post-treatment ... 13 
References ... 15 
Zinc Coatings - Guidelines and Recommendations for the
Protection Against Corrosion of Iron and Steel in Structures -
Part 3. Sherardizing
1 Scope
This Part of GB/T 19355 provides guidelines and recommendations to the fundamental
principle that is applicable to anti-corrosion sherardizing design of workpieces.
The sherardized coatings’ protection of workpieces depends on the construction
method of sherardized coatings, the design of workpieces and the specific
environment where workpieces are exposed to. Sherardized workpieces can adopt
additional coatings (beyond the range of this Part of GB/T 19355), for example, organic
coatings (wet coatings or powder coatings), which can provide further protection. This
combined coatings that are applied to sherardized workpieces are generally known as
“composite coating system”.
Please refer to ISO 12944-5 and EN 13438 for the basic guideline of this question.
The anti-corrosion maintenance of sherardized steel workpieces is beyond the range
of this Part of GB/T 19355.
Relevant requirements of specific products (for example, sherardized coatings of
fastening pieces or steel pipes) shall be prior to the basic recommendations in this Part.
2 Normative References
The following documents are indispensable to the application of this Standard. In terms
of references with a specified date, only versions with a specified date are applicable
to this Standard. The latest version (including all the modifications) of references
without a specified date is also applicable to this Standard.
GB/T 10123 Corrosion of Metals and Alloys - Basic Terms and Definitions (GB/T
10123-2001, ISO 8044.1999, eqv)
ISO 12944-5 Paints and Varnishes - Corrosion Protection of Steel Structures by
Protective Paint Systems - Part 5. Protective Paint Systems
ISO 18265 Metallic Materials - Conversion of Hardness Values
EN 13811 Sherardizing - Zinc Diffusion Coatings on Ferrous Products -
Specification
sherardized. Special measures shall be adopted, for example, filling up hollow
workpieces with sherardized mixtures can guarantee perfect sherardizing inside the
product.
Sherardizing is also applicable to spring and high-strength steel. In order to protect the
comprehensiveness of this type of workpieces from any influence, sherardizing shall
be conducted at an appropriate temperature in accordance with the quenching
temperature and tempering temperature of these workpieces. Spring shall be
sherardized at a few and unloaded state before being assembled. In accordance with
the thermal treatment temperature of these components before sherardizing,
sherardizing can be conducted within the range of a relatively low temperature of
320 °C ~ 380 °C. However, sherardizing at a relatively low temperature would prolong
the treatment time.
Workpieces with soft soldering or resin bonding shall not be sherardizing, because this
nature of welding will be influenced by the sherardizing process.
Welding shall be preferably conducted before sherardizing. All the welding shall leave
no residues. After sherardizing, workpieces can receive spot welding, but since the
sherardizing coating shall be relatively thin, the thickness of the sherardizing coat shall
be < 15 μm under the ideal state.
In terms of surface and holes with matching requirements, extra gap shall be reserved,
so that sherardizing coating with specific thickness (refer to EN 13811) can be
accepted.
Please refer to 4.4 for recommendations on the gap of threaded components
4.4 Gap of Threaded Components
Although sherardizing can form well-proportioned sherardizing coating with no
significant changes on the thread profile, sufficient gap must be retained between the
external and internal thread. Please refer to Table 1 for the recommended gap.
If only the external thread is sherardized, and it is matched with the standard non-
sherardized internal thread (or vice versa), half of the gap listed in Table 1 shall be
retained in threads that are sherardized.
Due to the alloy composition of zinc/ferroalloy coating, dark orange and brown rust
might be generated while being exposed to the outside. This cannot be confused with
the corrosion of matrix materials. It is a result of a change of the initial color of
zinc/ferroalloy coating caused by oxidization while being exposed to the external moist
condition.
This discoloration is harmless to the properties of sherardized coating and the
application of sherardized workpieces. Under continuous exposure, the surface color
would become dark, but the sherardized coating has a service life, which depends on
the thickness of the sherardized coating.
5.2 Recommendations for Storage and Transportation
If possible, tubular and other hollow sherardized workpieces shall be vertically placed
and naturally stored for later usage. They shall be prevented from accumulated water
or any other corrosive fluid. Large-sized workpieces shall be stored under dry condition.
Pay more attention to the storage of (large) thread materials and protect threads from
any damage.
The outdoor transportation of large-sized workpieces shall be handled under dry
condition. If possible, please them in (sealed) containers or packaging bags.
6 The Influence of Workpieces’ State on Sherardizing
Quality
6.1 Composition
Sherardizing is applicable to non-alloy carbon steel, low-alloy steel, sintering material,
malleable gray cast iron and cast iron. Spring steel and high-strength steel can obtain
relatively satisfying sherardized coating. In accordance with the quenching
temperature and tempering temperature of these components, sherardizing shall be
conducted at an appropriate temperature within the range of 320 °C ~ 380 °C.
The chemical composition of steel will not exert any practical influence on the
composition or thickness of the sherardized coating.
6.2 Surface Condition
Clean the surface of the matrix material before sherardizing.
Surface dirt cannot be eliminated through sandblasting. It shall be eliminated before
mechanical pre-treatment. The responsibility of eliminating the pollutants shall be
negotiated by sherardizing experts and the demand side.
6.3 The Influence of Surface Roughness on the Thickness of Sherardizing
thermal cycle control capability, steel’s mechanical properties might be reduced.
Therefore, consult experts’ opinions regarding the thermal treatment process that
eliminates stress.
In the welding area or the area affected by oxygen cutting, residual stress and
hardening might be formed. Its numerical value depends on different factors, such as
the length and thickness of welding, and the welding process.
Residual stress and hardening that exist in assembly parts might lead to damage and
deformation of workpieces’ coatings. Therefore, appropriate design and welding
technique shall be adopted to minimize the residual stress and hardening. In terms of
small important structural components, it is recommended that thermal treatment that
eliminates stress shall be increased. Extra thermal treatment might be obtained to
eliminate stress. Similar recommendation might also be applicable to drilling and
stamping procedure.
6.4.3 Hydrogen Embrittlement
During acid pickling, structural steel generally will not generate brittleness; if hydrogen
exists, it will not affect structural steel under general circumstances.
If steel hardness is > 34 HRC, 340 HV or 325 HB (refer to ISO 18265), minimize the
absorption of hydrogen during the surface pickling with hydrochloric acid. Generally
speaking, the hardness of welding and heat affected zone (HAZ) of structural steel will
not exceed 340 HV. Therefore, hydrogen embrittlement will not be triggered on these
areas during surface treatment.
During sherardizing, gradually heat up the workpieces to the processing temperature
(generally. 320 °C ~ 419 °C). Before the sherardized coating is formed, the absorbed
hydrogen can be released.
6.5 Large-sized Workpieces and Thick Steel
The thickness and dimension of steel workpieces will not exert any influence on the
formation of the sherardized coating, and the composition and nature of the
sherardized coating.
7 The Influence of Sherardizing on Workpieces
7.1 Processing Environment
The sherardized coating is closely related with the contour of the sherardized
workpiece. However, in terms of threaded components, gap deviation shall be
reserved on matching thread, so that the thickness of sherardized coating can be
acceptable. Please refer to the recommended gap in Table 1.
GB/T 19355.3-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.220.40
A 29
Partially replacing GB/T 19355-2003
Zinc Coatings - Guidelines and Recommendations for the
Protection Against Corrosion of Iron and Steel in Structures -
Part 3. Sherardizing
(ISO 14713-3.2009, MOD)
ISSUED ON. FEBRUARY 24, 2016
IMPLEMENTED ON. SEPTEMBER 1, 2016
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration Committee of the People’s
Republic of China.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative References ... 5 
3 Terms and Definitions ... 6 
4 Sherardizing Design ... 6 
5 Storage and Transportation ... 9 
6 The Influence of Workpieces’ State on Sherardizing Quality... 10 
7 The Influence of Sherardizing on Workpieces ... 12 
8 Post-treatment ... 13 
References ... 15 
Zinc Coatings - Guidelines and Recommendations for the
Protection Against Corrosion of Iron and Steel in Structures -
Part 3. Sherardizing
1 Scope
This Part of GB/T 19355 provides guidelines and recommendations to the fundamental
principle that is applicable to anti-corrosion sherardizing design of workpieces.
The sherardized coatings’ protection of workpieces depends on the construction
method of sherardized coatings, the design of workpieces and the specific
environment where workpieces are exposed to. Sherardized workpieces can adopt
additional coatings (beyond the range of this Part of GB/T 19355), for example, organic
coatings (wet coatings or powder coatings), which can provide further protection. This
combined coatings that are applied to sherardized workpieces are generally known as
“composite coating system”.
Please refer to ISO 12944-5 and EN 13438 for the basic guideline of this question.
The anti-corrosion maintenance of sherardized steel workpieces is beyond the range
of this Part of GB/T 19355.
Relevant requirements of specific products (for example, sherardized coatings of
fastening pieces or steel pipes) shall be prior to the basic recommendations in this Part.
2 Normative References
The following documents are indispensable to the application of this Standard. In terms
of references with a specified date, only versions with a specified date are applicable
to this Standard. The latest version (including all the modifications) of references
without a specified date is also applicable to this Standard.
GB/T 10123 Corrosion of Metals and Alloys - Basic Terms and Definitions (GB/T
10123-2001, ISO 8044.1999, eqv)
ISO 12944-5 Paints and Varnishes - Corrosion Protection of Steel Structures by
Protective Paint Systems - Part 5. Protective Paint Systems
ISO 18265 Metallic Materials - Conversion of Hardness Values
EN 13811 Sherardizing - Zinc Diffusion Coatings on Ferrous Products -
Specification
sherardized. Special measures shall be adopted, for example, filling up hollow
workpieces with sherardized mixtures can guarantee perfect sherardizing inside the
product.
Sherardizing is also applicable to spring and high-strength steel. In order to protect the
comprehensiveness of this type of workpieces from any influence, sherardizing shall
be conducted at an appropriate temperature in accordance with the quenching
temperature and tempering temperature of these workpieces. Spring shall be
sherardized at a few and unloaded state before being assembled. In accordance with
the thermal treatment temperature of these components before sherardizing,
sherardizing can be conducted within the range of a relatively low temperature of
320 °C ~ 380 °C. However, sherardizing at a relatively low temperature would prolong
the treatment time.
Workpieces with soft soldering or resin bonding shall not be sherardizing, because this
nature of welding will be influenced by the sherardizing process.
Welding shall be preferably conducted before sherardizing. All the welding shall leave
no residues. After sherardizing, workpieces can receive spot welding, but since the
sherardizing coating shall be relatively thin, the thickness of the sherardizing coat shall
be < 15 μm under the ideal state.
In terms of surface and holes with matching requirements, extra gap shall be reserved,
so that sherardizing coating with specific thickness (refer to EN 13811) can be
accepted.
Please refer to 4.4 for recommendations on the gap of threaded components
4.4 Gap of Threaded Components
Although sherardizing can form well-proportioned sherardizing coating with no
significant changes on the thread profile, suff...