In the ISO 22775 standard developed by the International Organization for Standardization (ISO), two methods are used to determine the tendency of a metal surface to either visually change due to contamination from atmospheric pollution (Method 1: sulfide tarnish) or to corrode under the influence of salt water (Method 2: salt water corrosion). different test methods are defined.
For the purposes of this standard, corrosion resistance refers to the tendency of a metal surface not to be visually affected by chemical attack from atmospheric pollution or altered by the action of salt water.
The first method defined in the ISO 22775 standard is sulfur blackening. In this method, the test sample is stored for one hour in a humid atmosphere containing a low concentration of hydrogen sulfide gas. The sample is then evaluated subjectively for signs of discoloration.
The second method defined in the ISO 22775 standard is salt water corrosion. In this method, cottongrass saturated with sodium chloride solution is wrapped around a test sample. This assembly is then stored in a sealed bag at room temperature for 24 hours. The test sample is then evaluated for signs of corrosion, subjectively for turf staining.
Atmospheric sulfur tarnishing and brine corrosion methods are intended to determine the tendency of a metal surface to change visually due to contamination from atmospheric pollution or to corrode under the influence of brine. These test methods are applied to all types of metal and metal-plated components.
Silver and silver alloy accessories generally darken when exposed to sulphide environments, causing some changes in their aesthetic appearance and electrical properties. Tarnishing occurs when silver reacts with gaseous reduced sulfur compounds from atmospheric pollution. Traditionally, different mechanical, chemical and electrochemical methods have been used to remove this tarnish. Today, the effects of the methods applied to remove tarnish on silver are still being investigated.
Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides testing services to determine the corrosion resistance of shoe accessories (metallic accessories) within the scope of ISO 22775 standard, with its trained and expert staff and advanced technological equipment.
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