ISO/TC 107/WG 2 - Vitreous and porcelain enamel coatings

This document specifies the requirements for the design and use of vitreous enamel coated bolted cylindrical steel tanks for the storage or treatment of water or municipal or industrial effluents and sludges. It is applicable to the design of the tank and any associated roof and gives guidance on the requirements for the design of the foundation. It is applicable where: a) the tank is cylindrical and is mounted on a load-bearing base substantially at or above ground level; b) the product of the tank diameter in metres and the wall height in metres lies within the range 5 to 500; c) the tank diameter does not exceed 100 m and the total wall height does not exceed 50 m; d) the stored material has the characteristics of a liquid, exerting a negligible frictional force on the tank wall; the stored material can be undergoing treatment as part of a municipal or industrial effluent treatment process; e) the internal pressure in the headspace above the liquid does not exceed 50 kPa and the internal partial vacuum above the liquid does not exceed 10 kPa; f) the walls of the tank are vertical; g) the floor of the tank is substantially flat at its intersection with the wall; the floor of the tank can have a rise or fall built in to allow complete emptying of the tank contents, the slope of which does not exceed 1:100; h) there is negligible inertial and impact load due to tank filling; i) the minimum thickness of the tank shell is 1,5 mm; j) the material used for the manufacture of the steel sheets is carbon steel (tanks constructed of sheets made from aluminium or stainless steel are outside the scope of this document); k) the temperature of the tank wall during operation is within the range −50 °C to +100 °C under all operating conditions. This document also gives details of procedures to be followed during installation on site and for inspection and maintenance of the installed tank. It does not apply to chemical-reaction vessels. It does not cover resistance to fire.

This document specifies the basic conditions concerning the method for determining the resistance of vitreous and porcelain enamelled articles to heat. The method specified is applicable to vitreous and porcelain enamelled articles that are, in service, subjected to high temperature, for example, to some cooker components, exhaust pipe silencers, gas heating chimneys and flue pipes.

This document specifies a method of test for determining the scratch hardness of the surface of vitreous and porcelain enamels.

This document specifies a test method for the determination of the crack formation temperature of enamels for the chemical industry by subjecting enamelled steel specimens to thermal shock using cold water. The value of the crack formation temperature measured according to this test method does not apply to the finished component (see Annex A). It is a parameter of vitreous and porcelain enamels for comparing the relative quality of different enamel formulations.

This document gives guidance on the selection of test methods for evaluating the performance of vitreous and porcelain enamelled finishes in different applications. This document references the test methods available for measuring the properties of these finishes and correlates these properties to the requirements of specific enamelled articles. This document is limited for the most part to test methods in ISO documents or European standards but does not provide acceptance criteria or performance limits for the properties. This document is applicable to all enamelled articles, irrespective of their basis metals.

This document specifies a simulating method of test for determination of the release of metal-ions from enamelled articles, which are intended to come into contact with food. This document also specifies limits for the release of metal-ions from enamelled articles, which are intended to come into contact with food. This document is applicable to enamelled articles, including tanks and vessels, which are intended to be used for the preparation, cooking, serving and storage of food.

This document specifies two low voltage tests for detecting and locating defects that extend to the basis metal in vitreous and porcelain enamel coatings. Method A (electrical) is applicable to the rapid detection and determination of the general location of defects. Method B (optical), based on colour effects, is applicable to the more precise detection of defects and their exact locations. Both methods are commonly applied to flat surfaces. For more intricate shapes, such as undulated and/or corrugated surfaces, ISO 8289-2 is applicable. NOTE 1 Selection of the correct test method is critical to distinguish the areas of increased conductivity detected by method B from actual pores that extend to the basis metal, which can be detected by both methods. NOTE 2 The low voltage test is a non-destructive method of detecting defects and, therefore, is completely different from the high voltage test specified in ISO 2746. The results of the high and low voltage tests are not comparable and will differ.

This document specifies a test method for determining the resistance of vitreous and porcelain enamel coatings to abrasion by rubbing, grinding or other mechanical effects.

This document specifies the quality requirements for apparatus, components, appliances and accessories of glass-lined steel (including semi-crystallized enamel coatings) and glass-lined steel castings used for process plants. It specifies the quality requirements and the tests to be carried out by the manufacturer as well as the actions to be taken to repair defects. It is also applicable to glass-lined pumps, pump components and fittings. It does not apply to glass-lined flanged steel pipes or glass-lined flanged steel fittings. NOTE 1 Provisions for glass-lined flanged steel pipes and glass-lined flanged steel fittings are given in ISO 28721-4. The test methods specified cover checking the enamel, the dimensional accuracy and the performance of apparatus and components. This document is applicable to new apparatus and components as well as used items that have been re-enamelled. It does not contain requirements regarding the chemical or physical properties of vitreous and porcelain enamels. NOTE 2 Examples of test reports are given in Annex A.

This document specifies the minimum requirements and the functional characteristics of enamel coatings applied by any process, such as wet dipping, wet flow-coating, wet spraying, wet electrostatic spraying, wet electrodeposition or dry-powder electrostatic spraying, to profiled steel heat exchanger panels in regenerative heat exchangers, before and after packing in baskets. For very severe service conditions, or to obtain extended operational life, more stringent limits can be agreed between customer and supplier.

This document specifies a low-voltage test method for detecting and locating defects (pores, cracks or pop-offs) that occur in enamel coatings of corrugated and/or undulated profiles and that extend down to the metal base. The method is based on colour effects (optical method) and is applicable to the precise detection of defects and their exact position. It can be used for non-flat, more profiled shapes such as corrugated or undulated surfaces. NOTE The low-voltage test is a non-destructive test for detecting defects extending down to the metal base and is, therefore, completely different in comparison to the high-voltage test in accordance with ISO 2746.

ISO 28706-3:2017 describes a test method for the determination of the resistance of vitreous and porcelain enamelled articles to attack by alkaline liquids at temperatures between 25 °C and 95 °C. The apparatus used is a hexagonal vessel in which six enamelled specimens or a tetragonal glass bottle in which four enamelled specimens are simultaneously tested. NOTE 1 The resistance to any alkaline liquid can be determined. However, the test method was originally used for the determination of the resistance to hot detergent solutions, within the neutral and alkaline range, used for washing textiles. NOTE 2 Since detergents are continually subject to alterations in their composition, a standard test solution is specified which, in respect to its alkalinity, wetting properties and complexing behaviour, can be considered as a typical composition for the detergents present on the market. The pH value and alkalinity of the standard test solution depend on the proportions of sodium tripolyphosphate, sodium carbonate and sodium perborate present; sodium tripolyphosphate acts simultaneously as a complexing agent. The wetting properties of the standard test solution are obtained by the addition of alkylsulfonate. A higher sodium perborate content is not considered necessary since the effect of oxygen on enamel is unimportant and an increase in the perborate content does not cause any significant alteration in the alkalinity of the standard test solution. The testing of different enamels using this standard test solution and other test solutions (including 5 % sodium pyrophosphate solution) has justified the use of this standard test solution for determining the resistance of enamels to hot detergent solutions.

ISO 20274:2017 specifies the procedures for the preparation of enamel samples for measurement of the thermal length change and calculation of the thermal expansion coefficient.

ISO 28706-2:2017 specifies a test method for the determination of the resistance of flat surfaces of vitreous and porcelain enamels to boiling acids, boiling neutral liquids, alkaline liquids and/or their vapours. This method allows the determination of the resistance of vitreous and porcelain enamels to the liquid and vapour phases of the corrosive medium simultaneously.

ISO 28721-5:2016 establishes a system for the cataloguing of defects in enamellings for chemical service and vessels. In addition, it describes some types of areas in which defects have been treated and which can easily be confounded with enamelling defects. It serves for a consistent language use concerning the designation and characterization of enamelling defects. ISO 28721-5:2016 is limited to detectable defects and does not purport to fully take into consideration all occurring types of defects. It does not evaluate enamelling defects; the classification carried out is based on experience and corresponds, as far as possible, to ISO 28721-1. NOTE Regarding the acceptance of glass lined equipment for use in process engineering, ISO 28721-1 applies.

ISO 28706-4:2016 describes a test method for the determination of the resistance of vitreous and porcelain enamelled articles to attack by alkaline liquids at temperatures between 25 °C and 95 °C. The apparatus used is a cylindrical vessel in which only one enamelled specimen is tested. NOTE 1 The test method was initially set up for determination of the resistance of vitreous and porcelain enamels to a hot sodium hydroxide solution. Within the scope of this part of ISO 28706, the resistance of other alkaline liquids can be tested. NOTE 2 This part of ISO 28706, which uses a cylindrical vessel, is generally used for tests carried out on vitreous and porcelain enamel coatings for the chemical industry.

ISO 28721-2:2015 specifies requirements for the resistance to chemical attack and thermal shock of chemical enamels and their designation for ordering purposes. It is applicable to enamelled apparatus, piping and other components primarily used for process equipment in chemical plants. It only applies to unalloyed and low-alloy carbon steels suitable for enamelling. NOTE The main criteria for assessing enamel quality are the resistance to chemical attack and thermal shock and the structure of the cover coat enamel.

ISO 28764:2015 specifies a method for the production of specimens suitable for testing vitreous and porcelain enamel coatings. It specifies two different specimens: - specimens taken from production articles; - specially produced specimens. NOTE Only the specially produced specimens can be used when the loss in mass per unit area of the enamel coating is to be determined quantitatively, as specimens cut from enamelled articles can reduce the accuracy of the test method.

ISO 28721-4:2015 specifies the quality requirements for glass-lined flanged steel pipes and flanged steel fittings used for process plants.

ISO 2746:2015 describes two test methods of high voltage testing: - Test A is used to detect and locate defects in vitreous and porcelain enamels; - Test B is used to detect and locate defects and weak spots in vitreous and porcelain enamels. The tests are performed using DC or pulsed DC high voltage. The tests are applicable to dry surfaces of enamel coatings. In the case of moist surfaces, care should be taken to ensure that the locating of any defects is correctly performed. Since test voltages depend on the coating thickness, the test method, especially with test A, may not be suitable for test specimens for which the coating thickness varies to a large extent.

ISO 4534:2010 specifies a comparative method of determining the fluidity behaviour of vitreous and porcelain enamels in the viscous condition during firing. It is not intended for use as an absolute method.

ISO 28762:2010 specifies the requirements for the functional and aesthetic characteristics of vitreous and porcelain enamel coatings applied to plain steel, for use as writing surfaces (whiteboards and chalkboards).

ISO 28706-5:2010 specifies a test method for the determination of the resistance of vitreous- and porcelain-enamelled articles to attack in closed systems by acid, neutral and alkaline liquids, as well as by actual process mixes. It applies primarily to the testing of enamels designed for use in chemical processes.

ISO 28721-3:2008 specifies requirements for the thermal shock resistance of, and heating and cooling procedures for, glass-lined apparatus, components, accessories and pipes primarily used for process equipment in chemical plants. It specifies the limits of thermal shock resistance using diagrams. For glass-lined steel, a distinction is made between a thermal shock on the glass-lined side (produced by charging an apparatus) and a thermal shock on the steel side (produced by heating or cooling an apparatus). This part of ISO 28721 applies to operating temperatures from - 25 °C to + 230 °C. It is only applicable to enamelled unalloyed and low-alloy carbon steels.

ISO 28706-1:2008 describes a test method for the determination of the resistance of vitreous and porcelain enamelled articles to attack by an acid at room temperature, and also specifies a method of classifying the results.

ISO 28723:2008 specifies a test method for the determination of the covering of the edge of enamelled steel plate to be used in heat exchangers. This method is applicable to all enamelling processes. It is applicable to plates with a thickness between 0,5 mm and 1,5 mm. The method is not applicable where the current flow generated in the test exceeds 3 A.

ISO 28722:2008 specifies the requirements for enamel-coated, plane, cold-rolled, heavy- and light-gauge steel panels intended for interior and exterior architectural use. It includes the functional and aesthetic characteristics and resistance to graffiti of these panels and the related coatings.

This International Standard specifies a test method for the accelerated determination of the resistance of porcelain enamel coatings on aluminium and aluminium alloys to spalling as a result of exposure to moisture or weathering. Because spalling is caused by the lack of adhesion between the coating and the base metal, the spall test is a test of adhesion. The greater the extent of spalling in this test, the greater the likelihood that the article will spall in service.

Specifies a test method which is used as a factory production control test. The test is not intended to be used for testing the adhesion of the enamel. Annexes A and B are for information only.

Specifies the requirements for the testing apparatus to be used. Includes a general description and figures.

Applies to enamelled walls of roasting devices, grills and baking devices; self-cleaning consists in the capacity first to absorb oil or fat in droplet form, and then to volatilize the greater part of the fat or oil by the sequential processes of distillation, decomposition, and combustion. Is not applicable to pyrolytically cleaning enamels.

This document specifies a simulating method of test for determination of the release of metal-ions from enamelled articles, which are intended to come into contact with food. It also specifies limits for the release of metal-ions from enamelled articles, which are intended to come into contact with food. It is applicable to enamelled articles, including tanks and vessels, which are intended to be used for the preparation, cooking, serving and storage of food.

ISO 28765:2016 establishes the requirements for the design and use of vitreous-enamel-coated bolted cylindrical steel tanks for the storage or treatment of water or municipal or industrial effluents and sludges. It applies to the design of the tank and any associated roof and gives guidance on the requirements for the design of the foundation. It applies where a) the tank is cylindrical and is mounted on a load-bearing base substantially at or above ground level; b) the product of the tank diameter in metres and the wall height in metres lies within the range 5 to 500; c) the tank diameter does not exceed 100 m and the total wall height does not exceed 50 m; d) the stored material has the characteristics of a liquid, exerting a negligible frictional force on the tank wall; the stored material may be undergoing treatment as part of a municipal or industrial effluent treatment process; e) the internal pressure in the headspace above the liquid does not exceed 50 kPa and the internal partial vacuum above the liquid does not exceed 10 kPa; f) the walls of the tank are vertical; g) the floor of the tank is substantially flat at its intersection with the wall; the floor of the tank may have a rise or fall built in to allow complete emptying of the tank contents, the slope of which does not exceed 1:100; h) there is negligible inertial and impact load due to tank filling; i) the minimum thickness of the tank shell is 1,5 mm; j) the material used for the manufacture of the steel sheets is carbon steel (tanks constructed of sheets made from aluminium or stainless steel are outside the scope of this International Standard); k) the temperature of the tank wall during operation is within the range −50 °C to +100 °C under all operating conditions. ISO 28765:2016 also gives details of procedures to be followed during installation on site and for inspection and maintenance of the installed tank. It does not apply to chemical-reaction vessels. It does not cover resistance to fire.

ISO 4528:2015 is a guide to the selection of test methods for evaluating the performance of vitreous and porcelain enamelled finishes in different applications. It references the test methods available for measuring the properties of these finishes and correlates these properties to the requirements of specific enamelled articles. It is limited for the most part to test methods that are described in International Standards or European Standards and does not provide acceptance criteria or performance limits for the properties. ISO 4528:2015 applies to all enamelled articles irrespective of their basis metals.

ISO 28721-4:2010 specifies the quality requirements for glass-lined flanged steel pipes and flanged steel fittings used for process plants.

ISO 28721-1:2008 specifies the quality requirements for apparatus, components, appliances and accessories of glass-lined steel (including semi-crystallized enamel coatings) and glass-lined steel castings used for process plants. It specifies the quality requirements and the tests to be carried out by the manufacturer as well as the action to be taken to repair defects. It is also applicable to glass-lined pumps, pump components and fittings. It is not applicable to glass-lined flanged steel pipes or glass-lined flanged steel fittings. The test methods specified cover checking the enamel, the dimensional accuracy and the performance of apparatus and components. This part of ISO 28721 applies to new apparatus and components as well as used items that have been re-enamelled. It does not contain requirements regarding the chemical or physical properties of vitreous and porcelain enamels.

ISO 28721-2:2008 specifies requirements for the resistance to chemical attack and thermal shock of chemical enamels and their designation for ordering purposes. It is applicable to enamelled apparatus, piping and other components primarily used for process equipment in chemical plants. It only applies to unalloyed and low-alloy carbon steels suitable for enamelling. NOTE The main criteria for assessing enamel quality are the resistance to chemical attack and thermal shock and the structure of the cover coat enamel.

ISO 28706-3:2008 describes a test method for the determination of the resistance of vitreous and porcelain enamelled articles to attack by alkaline liquids at temperatures between 25 °C and 95 °C. The apparatus used is a hexagonal vessel in which six enamelled specimens are simultaneously tested.

ISO 28706-5:2008 specifies a test method for the determination of the resistance of vitreous and porcelain enamelled articles to attack in closed systems by acid, neutral and alkaline liquids, as well as by actual process mixes. It applies primarily to the testing of enamels designed for use in chemical processes.

ISO 28706-4:2008 describes a test method for the determination of the resistance of vitreous and porcelain enamelled articles to attack by alkaline liquids at temperatures between 25 °C and 95 °C. The apparatus used is a cylindrical vessel in which only one enamelled specimen is tested.

ISO 28706-2:2008 describes a test method for the determination of the resistance of flat surfaces of vitreous and porcelain enamels to boiling acids, boiling neutral liquids and/or their vapours. The method allows the determination of the resistance of vitreous and porcelain enamels to the liquid and vapour phases of the corrosive medium simultaneously.

ISO 28762:2008 specifies the requirements for the functional and aesthetic characteristics of vitreous and porcelain enamel coatings applied to plain steel for use as writing surfaces (whiteboards and chalkboards).

ISO 28763:2008 specifies the minimum requirements and the functional characteristics of enamel coatings applied by any process, such as wet dipping, wet flow-coating, wet spraying, wet electrostatic spraying, wet electrodeposition or dry-powder electrostatic spraying, to profiled steel heat exchanger panels in regenerative heat exchangers, before and after packing in baskets.

ISO 28764:2008 specifies a method for the production of specimens suitable for testing vitreous and porcelain enamel coatings. It specifies two different specimens: specimens taken from production articles; specially produced specimens.

ISO 28765:2008 establishes the requirements for the design and use of vitreous-enamel-coated bolted cylindrical steel tanks for the storage or treatment of water or municipal or industrial effluents and sludges. It applies to the design of the tank and any associated roof and gives guidance on the requirements for the design of the foundation. It applies where the tank is cylindrical and is mounted on a load-bearing base substantially at or above ground level; the product of the tank diameter in metres and the wall height in metres lies within the range 5 to 500; the tank diameter does not exceed 100 m and the total wall height does not exceed 50 m; the stored material has the characteristics of a liquid, exerting a negligible frictional force on the tank wall; the stored material may be undergoing treatment as part of a municipal or industrial effluent treatment process; the internal pressure in the headspace above the liquid does not exceed 50 kPa and the internal partial vacuum above the liquid does not exceed 10 kPa; the walls of the tank are vertical; the floor of the tank is substantially flat at its intersection with the wall; the floor of the tank may have a rise or fall built in to allow complete emptying of the tank contents, the slope of which does not exceed 1:100; there is negligible inertial and impact load due to tank filling; the minimum thickness of the tank shell is 1,5 mm; the material used for the manufacture of the steel sheets is carbon steel (tanks constructed of sheets made from aluminium or stainless steel are outside the scope of this International Standard); the temperature of the tank wall during operation is within the range -50 °C to +100 °C under all operating conditions. This International Standard also gives details of procedures to be followed during installation on site and for inspection and maintenance of the installed tank. It does not apply to chemical-reaction vessels. It does not apply to tanks fitted with floating roofs. It does not cover resistance to fire.