EN ISO 28706-4, which is a European standard and later published by the International Standards Organization (ISO), describes a test method for determining the resistance of vitreous and porcelain enamelware to attack by alkaline liquids at temperatures between 25-95 degrees. The apparatus used is a cylindrical vessel in which only one enamel sample is tested.
This standard is based on the ISO 2734 standard, also published by ISO (ISO 2734 Vitreous and porcelain enamels - testing apparatus with alkaline liquids).
The test method described in the ISO 28706-4 standard was originally established for determining the resistance of vitreous and porcelain enamels to hot sodium hydroxide solution. However, this test method is also used when testing the resistance of other alkaline liquids. Using a cylindrical container, this standard is often used for testing on vitreous and porcelain enamel coatings for the chemical industry.
The etching of vitreous and porcelain enamels with aqueous solutions is a dissolution process. Silicon dioxide, the main component of enamel, forms a three-dimensional silica network. After hydrolysis it decomposes and forms silicic acid or silicates. These are released into the attacking environment. Other components, primarily metal oxides, are also hydrolyzed to form the corresponding hydrated metal ions or hydroxides. All corrosion products are more or less soluble in the attacking medium. The entire process results in a loss in mass per unit area.
For some aqueous solutions, the attack on the enamel proceeds linearly through the corrosion time, for other aqueous solutions, the attack on the enamel proceeds logarithmically throughout the corrosion time.
The most important parameters affecting the aqueous corrosion of enamel are enamel quality, temperature and pH value. Inhibitory effects from the limited solubility of silica may also contribute.
Our organization, among the numerous test, measurement, analysis and evaluation studies it has given for businesses in various sectors, with its trained and expert staff and advanced technological equipment, within the scope of EN ISO 28706-4 standard, with the cylindrical test device of vitreous and porcelain enamels and the chemical effects caused by alkaline liquids. It also provides corrosion resistance testing services.
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