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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 13912-2002 Metallic coatings - Hot dip galvanized coatings on fabricated iron and steel articles - Specifications and test methods. The following main technical changes have been made with respect to GB/T 13912-2002:
——3.16 “zinc melt” and 3.17” weld seepage” are added in “Terms and definitions”.
——4.2 “Base metal” in the original standard is included in 4.1 "General" of this standard; 4.1 “Information to be supplied by the purchaser” in the original standard is adjusted to Annex A of this standard.
——6.3 “Renovation of uncoated or damaged areas” in the original standard is adjusted to Annex E of this standard and supplemented.
——Clause 7 “Test method” in the original standard is canceled. 7.1 “Appearance test”, 7.3 “Adhesion test” and corresponding provisions in Clause 6 in the original standard are combined in this standard. 7.2 “Thickness measurement” in the original standard is adjusted to Annex D of this standard.
This standard has been redrafted and modified in relation to ISO 1461:2009 Hot dip galvanized coatings on fabricated iron and steel articles - Specifications and test methods.
Compared with ISO 1461:2009, this standard has been modified in structure by adjusting Annexes E and C of ISO 1461:2009 to Annexes C and E of this standard respectively.
The main technical deviations with respect to ISO 1461:2009 and their justifications are as follows:
——the adjustments of technical deviations are made for the normative references in this standard so as to adapt to the technical conditions of China. The adjustments are mainly reflected in Clause 2 "Normative references", which are shown in the following:
● ISO 752 is replaced by GB/T 470 which is modified in relation to the international standard (see 4.2);
● ISO 2859-1 is replaced by GB/T 2828.1 which is identical to the international standard (see 6.2.3);
● ISO 2859-2 is replaced by GB/T 2828.2 which is not identical to the international standard (see 6.2.3);
● ISO 2859-3 is replaced by GB/T 2828.3 which is identical to the international standard (see 6.2.3);
● ISO 2178 is replaced by GB/T 4956 which is identical to the international standard (see 6.2.2);
● ISO 3882 is replaced by GB/T 6463 which is identical to the international standard (see 6.2.2);
● ISO 2064 is replaced by GB/T 12334 which is identical to the international standard (see Clause 3);
● ISO 2808 is replaced by GB/T 13452.2 which is identical to the international standard (see 6.2.2);
● ISO 1460 is replaced by GB/T 13825 which is identical to the international standard (see 6.2.2);
● ISO 10474 is replaced by GB/T 18253 which is identical to the international standard (see Clause 7).
The following editorial changes have been made in this standard:
——standard name is changed as Metallic coatings - Hot dip galvanized coatings on fabricated iron and steel articles - Specifications and test methods;
——the contents of Clause 1 "Scope" are appropriately supplemented and adjusted according to GB/T 1.1-2009;
——Annexes C and E are adjusted according to the sequence mentioned in the text.
This standard was proposed by China Machinery Industry Federation.
This standard is under the jurisdiction of the National Technical Committee on Metallic and Non-metallic Coating of Standardization Administration of China (SAC/TC 57).
The previous editions of this standard are as follows:
——GB/T 13912-1992, GB/T 13912-2002.
Metallic coatings - Hot dip galvanized coatings on fabricated iron and steel articles - Specifications and test methods
1 Scope
This standard specifies the specifications and test methods for hot dip galvanized coatings on fabricated iron and steel articles. After-treatment/over-coating of hot dip galvanized articles is not covered in this standard.
This standard is applicable to hot dip galvanized coatings (containing not more than 2% of other metals) on fabricated iron and steel articles (including certain castings). It is not applicable to the following:
a) sheet, wire and woven or welded mesh products that are continuously hot dip galvanized;
b) tube and pipe that are hot dip galvanized in automatic plants;
c) hot dip galvanized products (e.g. fasteners) for which specific standards exist and which might include additional requirements or requirements which are different from those of this standard.
Note: Individual product standards may incorporate this standard for the coating by quoting its number, or may incorporate it with modifications specific to the product. Different requirements may also be made for galvanized coatings on products intended to meet specific regulatory requirements.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 470 Zinc ingots (GB/T 470-2008, ISO 752:2004, MOD)
GB/T 2828.1 Sampling procedures for inspection by attributes - Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection (GB/T 2828.1-2012, ISO 2859-1:1999, IDT)
GB/T 2828.2 Sampling procedures for inspection by attributes - Part 2: Sampling plans indexed by limiting quality (LQ) for isolated lot inspection (GB/T 2828.2-2008, ISO 2859-2:1985, NEQ)
GB/T 2828.3 Sampling procedures for inspection by attributes - Part 3: Skip-lot sampling procedures (GB/T 2828.3-2008, ISO 2859-3:2005, IDT)
GB/T 4956 Non-magnetic coatings on magnetic substrates - Measurement of coating thickness - Magnetic method (GB/T 4956-2003, ISO 2178:1982, IDT)
GB/T 6463 Metallic and other inorganic coatings - Review of methods of measurement of thickness (GB/T 6463-2005, ISO 3882:2003, IDT)
GB/T 12334 Metallic and other inorganic coatings - Definitions and conventions concerning the measurement of thickness (GB/T 12334-2001, idt ISO 2064:1996)
GB/T 13452.2 Paints and varnishes - Determination of film thickness (GB/T 13452.2-2008, ISO 2808:2007, IDT)
GB/T 13825 Metallic coatings - Hot dip galvanized coatings on ferrous materials - Gravimetric determination of the mass per unit area (GB/T 13825-2008, ISO 1460:1992, IDT)
GB/T 18253 Steel and steel products - Types of inspection documents (GB/T 18253-2018, ISO 10474: 2013, IDT)
ISO 3549 Zinc dust pigments for paints - Specifications and test methods
EN 1179 Zinc and zinc alloys - Primary zinc
EN 13283 Zinc and zinc alloys - Secondary zinc
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 12334 and the following apply.
3.1
hot dip galvanizing
formation of a coating of zinc and/or zinc iron alloys on iron and steel articles by dipping prepared steel or cast iron in a zinc melt
3.2
hot dip galvanized coating
coating of zinc and/or zinc iron alloys on iron and steel articles obtained by hot dip galvanizing
Note: The term “hot dip galvanized coating” is subsequently referred to as the “coating”.
3.3
coating mass
total mass of zinc and/or zinc alloys per area of iron and steel product surface, expressed in g/m2
3.4
coating thickness
total thickness of zinc and/or zinc alloys on steel and iron surface, expressed in μm
3.5
significant surface
part of the article covered or to be covered by the hot dip galvanized coating and for which the coating is essential for appearance and/or serviceability
3.6
control sample
hot dip galvanized article or group of articles from an inspection lot that is selected for sampling
3.7
reference area
area within which a specific number of single measurements are made
3.8
local coating thickness
mean value of coating thickness obtained from the specific number of measurements within a reference area for a magnetic test or the single value from a gravimetric test
3.9
mean coating thickness
mean value of the local thickness of the coating measured after sampling a “large” article or a lot of galvanized articles
Note: “Large” article herein refers to the article with significant surface larger than 2m2 (see 6.2).
3.10
local coating mass
value of coating mass for an area obtained from a single gravimetric test
3.11
mean coating mass
mean value of the coating masses determined by using the sample selected in accordance with Clause 5 in a gravimetric test in GB/T 13825 or by conversion of the mean coating thickness
3.12
minimum value of the coating thickness
lowest single measurement in a gravimetric test or lowest mean obtained from the specified number of measurements in a magnetic test within a reference area
3.13
inspection lot
hot dip galvanized articles in single order or single delivery
Note: The term “inspection lot” is subsequently referred to as the “lot”.
3.14
acceptance inspection
inspection of an inspection lot at the hot dip galvanizing works, unless otherwise specified
3.15
uncoated areas
areas on the iron or steel articles that do not react with the zinc melt
3.16
zinc melt
molten mass containing primarily zinc
3.17
weld seepage
emission of previously retained pretreatment solutions from narrow spaces between two closely contacting surfaces that have been subject to intermittent welding or from very small cavities (pinholes) in the welds of a galvanized article
4 General requirements
4.1 General
This standard sets out requirements for the contents of the zinc melt used to apply a galvanized coating to articles (see 4.2). The chemical composition and the surface condition (finish and roughness) of the base metal, the mass of the articles and the galvanizing conditions may affect the appearance, thickness, texture and physical/mechanical properties of the coating. This standard does not define any requirements regarding these points. Guidance on these parameters may be found in GB/T 19355.2[7].
4.2 Hot dip galvanizing bath
The hot dip galvanizing bath shall primarily contain zinc melt. The total of the other elements (as identified in GB/T 470, EN 13283 or EN 1179) in the zinc melt shall not exceed 1.5% by mass.
4.3 Information to be supplied by the purchaser
The information listed in A.1 and A.2 of Annex A shall be supplied by the purchaser.
4.4 Safety
Safety measures shall be provided in the manufacturing of hot dip galvanized articles.
5 Acceptance inspection and sampling
Acceptance inspection shall be undertaken before the products leave the hot dip galvanizing works, unless otherwise specified at the time of ordering by the purchaser. Acceptance inspection involves assessment of the coating appearance and measurement of the coating thickness. Adhesion tests are normally not carried out and are only carried out by agreement.
The control sample for coating thickness test shall be taken randomly from each inspection lot (see 3.13), and the minimum number of articles from each inspection lot that forms the control sample shall be in accordance with Table 1.
Foreword i
1 Scope
2 Normative References
3 Terms and definitions
4 General requirements
4.1 General
4.2 Hot dip galvanizing bath
4.3 Information to be supplied by the purchaser
4.4 Safety
5 Acceptance inspection and sampling
6 Coating requirements
6.1 Appearance
6.2 Thickness
6.3 Renovation
6.4 Adhesion
6.5 Acceptance criteria
7 Certificate of compliance
Annex A (Normative) Information to be supplied
Annex B (Normative) Safety requirements
Annex C (Informative) Corrosion resistance of hot dip galvanized coatings
Annex D (Informative) Determination of thickness
Annex E (Informative) Renovation of uncoated or damaged areas
Bibliography
金属覆盖层 钢铁制件热浸镀锌层
技术要求及试验方法
1 范围
本标准规定了钢铁制件热浸镀锌层的技术要求和试验方法。本标准对热浸镀锌产品的后处理和保护涂层未做规定。
本标准适用于钢铁制件(包括某些铸件)的热浸镀锌层(其他合金元素总含量不超过2%)。本标准不适用于下列情况：
a) 连续式热浸镀锌生产的板材、线材、编织物或焊接网；
b) 自动化设备热浸镀锌生产的管材和棒材；
c) 采用特殊标准的热浸镀锌产品(如紧固件)、有附加要求或有与本标准要求不一致的热浸镀锌产品。
注：某些产品标准可能通过引用本标准或修改本标准部分条款来规定其产品的热浸镀层要求。也可以对产品的镀锌层做出不同规定以满足特定的要求。
2 规范性引用文件
下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件，仅注日期的版本适用于本文件。凡是不注日期的引用文件，其最新版本(包括所有的修改单)适用于本文件。
GB/T 470 锌锭(GB/T 470—2008，ISO 752：2004，MOD)
GB/T 2828.1 计数抽样检验程序 第1部分：按接收质量限(AQL)检索的逐批检验抽样计划(GB/T 2828.1—2012，ISO 2859-1：1999，IDT)
GB/T 2828.2 计数抽样检验程序 第2部分：按极限质量(LQ)检索的孤立批检验抽样方案(GB/T 2828.2—2008，ISO 2859-2：1985，NEQ)
GB/T 2828.3 计数抽样检验程序 第3部分：跳批抽样程序(GB/T 2828.3—2008，ISO 2859-3：2005，IDT)
GB/T 4956 磁性基体上非磁性覆盖层 覆盖层厚度测量 磁性法(GB/T 4956—2003，ISO 2178：1982，IDT)
GB/T 6463 金属和其他无机覆盖层厚度测量方法评述(GB/T 6463—2005，ISO 3882：2003，IDT)
GB/T 12334 金属和其他非有机覆盖层 关于厚度测量的定义和一般规则(GB/T 12334—2001，idt ISO 2064：1996)
GB/T 13452.2 色漆和清漆 漆膜厚度的测定(GB/T 13452.2—2008，ISO 2808：2007，IDT)
GB/T 13825 金属覆盖层 黑色金属材料热镀锌层 单位面积质量称量法(GB/T 13825—2008，ISO 1460：1992，IDT)
GB/T 18253 钢及钢产品 检验文件的类型(GB/T 18253—2018，ISO 10474：2013，IDT)ISO 3549 色漆用锌粉颜料 规范和试验方法(Zinc dust pigments for paints—Specifications and test methods)
EN 1179 锌及锌合金 初级锌(Zinc an zinc alloys—Primary zinc)
EN 13283 锌及锌合金 二次锌(Zinc and zinc alloys—Secondary zinc)
3 术语和定义
GB/T 12334界定的以及下列术语和定义适用于本文件。
3.1
热浸镀锌 hot dip galvanizing
将经过前处理的钢或铸铁制件浸入熔融的锌浴中，在其表面形成锌和(或)锌-铁合金镀层的工艺过程和方法。
3.2
热浸镀锌层 hot dip galvanized coating
采用热浸镀锌方法在钢铁件表面上获得的锌和(或)锌-铁合金镀层。
注：在本标准中简称镀层。
3.3
镀层的镀覆量 coating mass
钢铁表面上单位面积锌和(或)锌-铁合金镀层的总质量，以g/m2 表示。
3.4
镀层厚度 coating thickness
钢铁表面上锌和(或)锌-铁合金镀层的总厚度，以μm 表示。
3.5
主要表面 significant surface
制件上被热浸镀锌或将被热浸镀锌的部分表面，该部分表面上的镀层对于制件的外观和(或)使用性能是极为重要的。
3.6
样本 control sample
从检查批中随机抽取用于试验的热浸镀锌制件或制件组。
3.7
基本测量面 reference area
按规定次数进行检测试验的区域。
3.8
镀层局部厚度 local coating thickness
在某一基本测量面按规定次数用磁性法所测得的镀层厚度的算术平均值或用称量法进行一次测量所测得的镀层镀覆量的厚度换算值。
3.9
镀层平均厚度 mean coating thickness
对某一大件或某一批镀锌件抽样后测得镀层局部厚度的算术平均值。
注：本标准中大件是指主要表面大于2m2 的制件(见6.2)。
3.10
镀层局部镀覆量 local coating mass
采用称量法进行一次测量所测得的某一区域镀层的镀覆量。
3.11
镀层平均镀覆量 mean coating mass
按第5章规定抽样，用GB/T 13825规定的称量法测得的镀层局部镀覆量的算术平均值，或镀层平均厚度的换算值。
3.12
镀层厚度最小值 minimum value of the coating thickness
在基本测量面上用称量法测得的镀层镀覆量厚度换算值中的最小值，或按规定次数用磁性法所测得的镀层厚度的算术平均值中的最小值。
3.13
检查批 inspection lot
一次订货或一次交货的热浸镀锌制件。
注：在本标准中简称批。
3.14
验收检查 acceptance inspection
在没有其他规定的情况下，应在热浸镀锌生产厂家内对某检查批的热浸镀锌制件进行的检查。
3.15
漏镀面 uncoated areas
钢铁制件表面未与熔融锌发生反应的区域。
3.16
熔融锌 zinc melt
主要包含锌的熔融体。
3.17
焊缝渗流 weld seepage
热浸镀锌制件焊接处，之前残留的预处理溶液从两个交叠表面之间不连续焊接造成的狭窄空间或焊缝中极小的孔洞(针孔)中流出。
4 一般要求
4.1 概述
本标准规定了用于制件热浸镀锌层熔融锌的含量要求(见4.2)。基体金属的化学成分、表面状况(光洁度和粗糙度)、制件的质量及镀锌条件都可能影响锌镀层的外观、厚度、组织结构和物理/机械性能。本标准没有对这些影响因素提出具体要求，可以参考GB/T 19355.2[7]。
4.2 热浸镀锌浴
用于热浸镀锌的锌浴主要应由熔融锌构成。熔融锌中的杂质总含量不应超过总质量的1.5%(所指杂质见GB/T 470、EN 13283或EN 1179规定)。
4.3 需方应提供的资料
需方应提供附录A 中A.1和A.2所列的资料。
4.4 安全
在热浸镀锌的生产过程中应按附录B的要求采取安全措施。
5 验收和抽样
除非订货时需方提出其他要求，验收检查应在产品离开镀锌厂家之前进行。验收包括镀层外观评定和镀层厚度测量。镀层附着力通常不测试，或者只是根据供需双方协议进行测试。
用于镀层厚度试验的样本应从每一检查批(见3.13)中随机抽取，应按表1要求从每一检查批中抽取不少于最小数量的制件组成样本。
表1 检查批对照样本数量
检查批的制件数量 样本所需制件的最小数量
1~3 全部
4~500 3
501~1200 5
1201~3200 8
3201~10000 13
>10000 20
6 镀层的要求
6.1 外观
验收检查时，采用正常或矫正视力在1m 以上距离目测所有热浸镀锌制件，其主要表面(见3.5)应平滑，无滴瘤、粗糙和锌刺(如果这些锌刺会造成伤害)，无起皮(即下层无固体金属的凸起区域)，无漏镀，无残留的溶剂渣。
热浸镀锌层主要用于防止基体钢铁制件腐蚀，其美观和装饰性是次要的。如果在某些应用场合这些次要特性也很重要时，非常建议供需双方根据所达成的铁或钢制件(全部或部分)的光洁度标准，来确定钢铁制件所用的原材料成分范围。当要求的光洁度标准超出本条的规定时，这一点尤其重要。需要注意的是，“粗糙”和“平滑”是相对概念，制件镀层的粗糙度不同于经机械辊挤的镀锌制品(如镀锌钢板、管材和镀锌钢丝)的粗糙度。
只要镀层厚度大于规定值，被镀制件表面允许存在暗灰色或浅灰色的色彩不均匀区域(如网状花纹或暗灰色的区域)。潮湿条件下储存的镀锌制件，表面允许有白锈(以碱式氧化锌为主的白色或灰色产物)存在。
注：在某些情况下(例如，热浸镀锌制件需后处理或附加涂层时)，需方可向供方提出要求：
a) 镀锌后不进行水冷，和/或
b) 在储运过程中采取相应措施防止镀锌层表面腐蚀。
热浸镀锌制件表面不允许残存熔剂渣。可能影响热浸镀锌制件的使用或耐蚀性能的部位不应有锌瘤和锌灰(参见GB/T 19355.1[6]耐腐蚀性能数据)。
在交叠表面焊接中因使用不连续焊接而使镀层美观受到影响(如焊缝渗流)不应视为拒收的理由。使用这种焊接方式通常是出于健康和安全考虑，详细指南参见GB/T 19355.2[7]。
目测外观，检查不合格的制件应依照6.3进行修复或重镀后再重新检查。
若有特殊要求时(例如，热浸镀锌后需要涂装的)，应按需方要求提供样本[见A.2f)]。
6.2 厚度
6.2.1 概述
热浸镀锌层是为了保护钢铁产品不受腐蚀而设计的(参见附录C)。这种镀层的防腐时间长短基本与镀层厚度成正比(参见GB/T 19355.1[6])。在极严酷的腐蚀条件下服役和(或)要求较长服役时间的制件，其镀层厚度要求可以高于本标准的规定要求。
6.2.2 试验方法
当试验方法存在异议时，镀层厚度的计算方法应按GB/T 13825规定的热镀锌层单位面积称量法进行试验。采用称量法测得每单位面积上的平均镀层质量，再根据镀层的公称密度(7.2g/cm3)计算镀层厚度。当制件数少于10件时，需方可以不采纳称量法测量厚度，因为采用称量法可能破坏制件，给需方造成不可补救的经济损失。
厚度测量(参见附录D)通常由GB/T 13452.2和GB/T 4956规定的(或在GB/T 6463中指定)磁性方法之一进行。磁性法测量仪可测定永磁体和基体金属的磁引力，该磁引力受镀层的影响，或测定穿过镀层和基体金属的磁通路径磁阻。可选择方法有称量法和横断面显微镜法(参见附录D)。
在GB/T 4956、GB/T 6463和GB/T 13452.2中规定的测试方法最适合在工厂内进行在线质量控制。由于该方法测量的每个区域都非常小，个别测量值可能低于镀层的局部厚度或平均厚度值。如果用磁性法在一个基本测量面内进行了足够次数的测量，测得的局部厚度值将趋近于用称量法测得的局部厚度值。
6.2.3 基本测量面
为了获得尽可能具有代表性的镀层平均厚度(见3.9)或镀覆量(见3.11)，采用磁性法或称量法测量镀层厚度时，基本测量面的数量、位置及尺寸应根据制件形状和大小确定。对样本中较长制件，其基本测量面应在离其每端大约100mm、大致接近中心线的位置获取，并应包括制件的整个横截面。
