This article introduces the current status of domestic standards for powder coatings, the differences in standards compared to liquid coatings, and emphasizes that the development of the powder coating industry cannot be separated from the development of standards; The focus was on analyzing the current status of powder coating standards for domestic drinking water transmission and distribution equipment, as well as the current status of powder coating standards in the field of heavy-duty anti-corrosion.

Keywords: powder coating; national standard; Industry standards; Standard for powder coating for drinking water transmission and distribution equipment; Standard for heavy-duty anti-corrosion coatings

introduction

As of 2018, statistical data shows that the market share of powder coatings in the entire coatings market is still less than 10%. With the increase of national policies and regulations on VOCs control; Oil to water conversion& ldquo; Oil to powder conversion& ldquo; High solid content; Becoming several hot topics. Although powder coatings are limited by high temperature baking and substrate compared to water-based or high solid content paints, their application prospects cannot be underestimated with the breakthrough of technological bottlenecks in powder coatings. With the increase in the application industry of powder coatings and the expansion of the market, there is a corresponding demand for standards. And standards are the fundamental driving force for the development of the entire industry. The powder coating industry association, manufacturing enterprises, and related upstream and downstream enterprises have the responsibility to actively participate in or lead the formulation and suggestions of powder coating related standards, and jointly create a good environment and atmosphere for the development of the industry. First rate enterprises set standards, second rate enterprises establish brands, and third rate enterprises establish products. Leading industry standards and serving as industry benchmarks should be the ultimate goal pursued by every excellent enterprise.

Looking at the national standards related to powder coatings, powder coatings have a shorter development history and lower market share compared to oil-based coatings. The development of standards is also relatively backward, and there are relatively few relevant standards. As of now, there are only 35 current standards directly related to powder coatings in national standards, including 20 national standards, 13 industry standards, and 2 local standards; There are four industry standards specifically for the transportation industry, seven for the chemical industry, and one each for non-ferrous metals and railway transportation. However, in reality, the application fields of powder coatings are much wider than this. That is to say, many industries lack the standard requirements for powder coatings. In recent years, a series of reforms have been carried out in national standards, among which the National Standards Committee has proposed the concept of "; Chinese Standard 2035;, Aim to reform, improve, and optimize Chinese standards, making them at the forefront of the world.   On June 5, 2019, the Zhongguancun Materials Testing Technology Alliance released two group standard projects for powder coatings: "Powder Coatings for Professional Operation Vehicles" and "Determination of Fluorine Content in Powder Coatings Using Ionic Electrode Method". The former will be of great significance for standardizing and improving the level of powder coatings for specialized work vehicles, while the latter will lay the foundation for developing standards for fluorocarbon powder coatings. In addition to being used in the field of specialized work vehicles and ultra weather resistant fluorocarbon powder coatings, powder coatings are also applied in industries such as heavy-duty anti-corrosion, insulated electronics, insulated busbars, high reflection buildings, domestic and drinking water valve accessories, transportation road guardrails, automotive spare parts, new energy vehicles, photovoltaic power generation, lighting, etc. Because drinking water is closely related to people's livelihoods, and powder coatings have great potential in the field of heavy anti-corrosion, the following will focus on introducing the standard situation in these two fields.

The current status of powder coating standards for drinking water transmission and distribution equipment in China and the relevant standards for protective coatings for water transmission and distribution equipment can be found in Table 1. In the field of water transmission and distribution, coatings are protective materials used for water transmission and distribution. The National Health Commission has specified the safety performance of protective materials in GB/T 17219-1998 "Safety Evaluation Standards for Drinking Water Transmission and Distribution Equipment and Protective Materials", requiring sprayed pipe fittings to undergo immersion testing. The soaked water must meet the toxicity and water quality requirements in the national mandatory standard GB 5749-2006 "Sanitary Standards for Drinking Water". In China, each provincial Health Commission and Quality Supervision Bureau has its own“ Measures for Supervision and Administration of Health Administrative Licensing; And“ Measures for Supervision and Management of Drinking Water for Daily Life;, Related to coatings, it is necessary to conduct on-site audits of protective material production enterprises to ensure that the factory's location, raw materials used, production and manufacturing processes, as well as the quality and health conditions of workers meet the requirements. This indeed ensures the quality of drinking water in a great sense. However, after burying the pipelines, valves, and other fittings for water transmission and distribution underground, in the actual soil environment, a single immersion toxicity test of the fittings before installation is not sufficient to ensure long-term corrosion resistance. For coatings, necessary mechanical properties can prevent cracking when the coating is impacted, and necessary anti-corrosion properties can provide long-lasting protection for metal in buried environments. And a very important part of the protective performance of coatings is reflected in spray coating construction. How to ensure correct pre-treatment, application of correct construction conditions, and complete curing of coatings on equipment is also missing in the current domestic certification system. In different industries, there are generally standards for water transmission and distribution, but the requirements of these standards vary greatly. In the water conservancy engineering industry, there is an important industry standard SL 105-2007 "Corrosion Protection Specification for Hydraulic Metal Structures", which specifies the appearance, thickness, and adhesion of pre-treatment and coating, but does not mention mechanical properties and corrosion resistance. Multiple landmarks in this field, such as DB13T/2802-1028 "Technical Specification for Cast Iron Gates in Hydraulic Engineering", DB32T/2334.3-2013 "Specification for Quality Inspection and Evaluation of Hydraulic Engineering Construction Part 3: Metal Structures and Hydraulic Machinery", as well as the national standard GB/T 14173-2008 "Specification for Manufacturing, Installation and Acceptance of Steel Gates in Hydraulic and Hydroelectric Engineering", have referenced the requirements of SL 105-2007 in terms of coating. In the urban construction industry, two industry standards, CJ/T 120-2016 "Plastic coated composite steel pipes for water supply" and CJ/T 216-2005 "Soft sealed gate valves for water supply and drainage", require coatings for steel pipes and gate valves to meet the requirements of not affecting water quality, thickness, hardness, adhesion, and hygiene performance. The standard also does not mention mechanical properties and corrosion resistance. In the field of steel industry, GB/T34202-2017 "Epoxy Coating for Ductile Iron Pipes, fittings and Accessories" specifies the thickness, electrical breakdown, MIBK wiping, adhesion, impact, indentation, hot water immersion, acid and alkali resistance, wear resistance, and hygiene performance requirements for epoxy coatings used in cast iron valve fittings. Except for the lack of mention of corrosion resistance, all other requirements are relatively comprehensive. In the oil and gas industry, the requirements for coatings are the strictest, and regulations have been made for the internal and external application of fused sintered epoxy powder coatings: SY/T 0442-2010 "Technical Standard for Internal Anti corrosion Coating of Steel Pipeline Fused Epoxy Powder" and SY/T0315-2013 "Technical Specification for External Coating of Steel Pipeline Fused Epoxy Powder". The standard specifies requirements for the performance of powder coatings and coatings. For example, for external coatings, powder performance requirements include curing time, coking time, particle size, thermal characteristics, density, and magnetic content; Coating performance requirements: appearance, thermal characteristics, cathodic peel off, bending resistance, impact resistance, bonding surface and cross-sectional porosity, scratch resistance, wear resistance, electrical strength, electrical resistivity, cathodic peel off resistance after bending, and chemical corrosion resistance of the coating. It can be said that the performance requirements are already very comprehensive and can be used as an important reference standard for improving coating standards in the field of drinking water. However, the transportation requirements and hazard levels of petroleum are higher than those of water transportation, and the actual requirements need to be adjusted appropriately. However, due to the fact that domestic steel pipelines are still mainly coated with cement mortar and oil paint inside and outside, the application of powder coatings still requires more attempts and the development of supporting casting processes. At present, the application of powder coating is mainly for cast iron parts such as valves, connectors, and water storage tanks. In summary, in order to improve the quality of drinking water, industry standards for oil and gas pipelines can serve as an important reference for improving coating standards in this field. At the same time, combined with the German DVGW certification system, the American NSF certification system, and the Australian/New Zealand AS/NZS4020 certification system, the certification system can be improved while the standards are raised. Table 1 List of relevant standards for coatings used in domestic water transmission and distribution equipment