CEN/TC 262/WG 5 - Vitreous enamel coatings

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 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 International Standard specifies a method of determining, by successive thermal shock tests, the
behaviour of vitreous and porcelain enamelled cooking utensils and similar articles under sudden
changes of temperature (resistance to thermal shock).

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.

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.

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

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 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 the requirements for product quality and product testing of enamelled valves and pressure pipe fittings for untreated and potable water supply.
It does not apply to chemical service glass-enamel and apparatus enamel.

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 19496-1:2017 defines a number of terms relating to vitreous and porcelain enamels and their technology. This list is not complete and only comprises those terms for which the definition is considered necessary for correct and adequate understanding in order to clarify these processes.
The interpretations given are those corresponding to the practical usage in this field and they do not necessarily coincide with those used in other fields.
For purposes of clarification, the term "vitreous enamel", used throughout this document, is synonymous with "porcelain enamel", the term favoured in the United States and some other countries.

ISO 19496-2:2017 establishes a system for the cataloguing of defects in sheet steel enamelling. It serves for a consistent language use concerning the designation and characterization of enamelling defects. This document 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 serves for the conveyance of practical knowledge.

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 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.

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.

Test method for determination of scratch resistance of enamel finishes. Provides measure of durability of porcelain enamel finishes to scratching by sharp objects under high forces. Not to be confused with 'scratch hardness', which is measured by the procedure given in EN 101.

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

This International Standard 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 is not valid for the finished
component (see annex A). It is a parameter of vitreous and porcelain enamels for comparing the relative quality of
different enamel formulations.

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.

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.

Two low voltage tests for detecting and locating defects that extend to the basis metal in vitreous and porcelain enamel coatings.

ISO 11177:2016 specifies the requirements for product quality and product testing of enamelled valves and pressure pipe fittings for untreated and potable water supply. It is not applicable for chemical service glass-enamel and apparatus enamel.

This European Standard defines a number of terms relating to vitreous and porcelain enamels and their technology. This list is not complete and only comprises those terms for which the definition is considered necessary for correct and adequate understanding in order to clarify these processes.
It should be understood that the interpretations given are those corresponding to the practical usage in this field and that they do not necessarily coincide with those used in other fields.
For purposes of clarification, the term Vitreous Enamel, used throughout this European Standard, is synonymous with Porcelain Enamel, the term favoured in the United States and some other countries.

This document describes 2 test methods of high voltage testing:
¾   Test A is used to detect and locate defects in vitreous and porcelain enamels;
¾   Test B is used to detect and locate defects and weak spots in vitreous and porcelain enamels.
The tests are performed using DC, pulsed DC, or AC 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.
NOTE   This document extends the range of application of the test given in ISO 2746, which is restricted to coating thicknesses of minimum 660 µm.

This International Standard 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 requirements of specific enamelled articles. It is limited for the most part to test methods that are described in ISO International Standards and does not provide acceptance criteria or performance limits for the properties. This International Standard applies to all enamelled articles irrespective of their basis metals.

This European Standard specifies the quality requirements for glass lined flanged steel pipes and flanged
steel fittings.

This part of EN 14483 describes a test method for the determination of resistance to attack in closed systems by acid and neutral liquids, as well as by actual process mixes, the given corrosive agent generally applied at a temperature above its boiling point.
It is also applicable to the determination of resistance to mildly alkaline fluids provided that the material of the test equipment is suitable for such a test (see also 4.1.2).
This European Standard primarily applies to the testing of enamels designed for use in chemical process technology.

This part of EN 14483 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 in this section is a hexagonal vessel in which 6 enamelled specimens are simultaneous tested.
NOTE 1   The resistance to any alkaline liquid can be tested. However, the test method was original made 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 property and complexing behaviour, can be considered as a typical composition for the detergents at 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 property of the standard test solution is obtained by the addition of alkylsulphonate.  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 considerable 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.

This part of EN 14483 describes a test method for the determination of vitreous and porcelain enamelled articles to resistance 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 standard the resistance of other alkaline liquids can be tested.
NOTE 2   This part of EN 14483, which uses a cylindrical vessel is generally used for tests carried out on vitreous and porcelain enamel coatings for the chemical industry.

This part of EN 14483 describes a test method for the determination of the resistance of flat surfaces of vitreous and porcelain enamels to boiling acids, neutral 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.

This part of EN 14483 describes a test method for the determination of resistance of vitreous and porcelain enamelled articles to attack by an acid at room temperature, and also specifies a method of classifying results.

This European Standard specifies requirements on thermal shock resistance as well as heating and cooling procedures of standardised glass-lined apparatus, components, accessories, and glass-lined pipes primarily used for process equipment in chemical plants.
It specifies the limits of thermal shock resistance using diagrams (see Figure 1 and Figure 2). For
glass-lined steel, a difference is made between a thermal shock on the glass-lined side (by charging an apparatus) versus a thermal shock on the steel side (by heating and cooling an apparatus).
This European Standard applies to operating temperatures from - 25 °C to + 230 °C.
This European Standard is only applicable to enamelled unalloyed and low-alloy carbon steels.

This European Standard specifies the quality requirements for apparatus, components, appliances and accessories of vitreous glass lined steel (including semi-crystallized enamel coatings) and steel cast used for process plants. It specifies the quality requirements and the tests to be carried out by the manufacturer as well as the necessary actions for repairing defects.
This European Standard is also applicable to glass lined pumps, pump components and fittings.
This European standard is not applicable to glass-lined flanged steel pipes and flanged steel fittings.
NOTE 1   Provisions for glass-lined flanged steel pipes and flanged steel fittings are given in DIN 2876 [1].
The test methods specified cover checking the enamel, dimensional accuracy and performance of apparatus and components.
This European Standard applies to new apparatus and components as well as used ones that have to be re-enamelled.
This European Standard does not contain requirements regarding the chemical and physical properties of vitreous and porcelain enamels.
NOTE 2   Examples of test reports are given in Annex A.

This European Standard 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, components and piping components primarily used for process equipment in chemical plants.
This European Standard 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.

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

This European Standard 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.
This method is not applicable where the current flow generated in the test exceeds 3 A.

This document 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 European Standard specifies the requirements for the functional and aesthetic characteristics of vitreous or porcelain enamel coatings applied to plain steel for use as writing surfaces (whiteboards and chalkboards).

This European Standard specifies the requirements for the functional and aesthetic characteristics of vitreous or porcelain enamel coatings applied to plain steel for use as writing surfaces (whiteboards and chalkboards).