BR-UL-MCT Metallic Coating Thickness Test System
Implementation of standards: UL 1703-20015, ASTM B499-2009, ISO 2178-1995

The test for corrosive atmosphere Test, include salt spray test and moist carbon dioxide / sulphur dioxide, measure the thicknees of coating on Zinc-coated (galvanized) Iron or steel articles. Recommend ASTM B499 and ISO 2178 Nonmagnetic coatings on magnetic basis metals measurement of coating method. UL 1703-2008 use mass loss method (chemical method), Maneuverability is not strong, and chemical reagent may pollute the environment.


The method for determining the thickness of a zinc or cadmium coating mentioned in 14.1 and 14.2 is described in following.
The solution to be used for the metallic coating thickness test is to be made from distilled water and is to contain 200g/L of reagent (or better) grade chromium trioxide (CrO₃) and 50g/l of reagent (or better) grade concentrated sulfuric acid (H2_SO₄). The latter is equivalent to 27ml/l of reagent grade concentrated sulphuric acid, specific gravity 1.84, containing 96 percent of H₂SO₄.
The test solution is to be contained in a glass vessel such as a separatory funnel with the outlet equipped with a stopcock and a capillary tube of approximately 0.64 mm inside bore and 150mm long. The lower end of the capillary tube is to be tapered to form a tip, the drops from which are about 0.05 milliliter each. To preserve an effectively constant level, a small glass tube is to be inserted in the top of the funnel through a rubber stopper and its position is to be adjusted so that when the stopcock is open, the rate of dropping is 100±5 drops/min. If desired, an additional stopcock may be used in place of the glass tube to control the rate of dropping.
The sample and the test solution are to be kept in the test room long enough to acquire the temperature of the room, which 首ld be noted and recorded. The test is to be conducted at a room temperature of 21.2°C~32.0°C.
The sample is to be thoroughly cleaned before testing. All grease, lacquer, paint, or other nonmetallic coatings, including skin oils, are to be removed completely by means of solvents. The sample is then to be thoroughly rinsed in water and dried with clean cheesecloth.
The sample to be tested is to be supported from 17mm to 25mm below the orifice. The surface to be tested shall be inclined at approximately 45 degrees from the horizontal so that the drops of solution strike the point to be tested and run off quickly.
The stopcock is to be opened and the time in seconds is to be measured until the dropping solution dissolves the protective metal coating, exposing the base metal. The end point is the first appearance of the base metal recognizable by the change in color at that point.
The sample of a test lot is to be subjected to the test at three or more points, excluding cut, stenciled, and threaded surfaces, on the inside surface and at an equal number of points on the outside surface, at places where the metal coating may be expected to be the thinnest. (On enclosures made from precoated sheets, the external corners that are subjected to the greatest deformation are likely to have thin coatings.)
To calculate the thickness of the coating being tested, select from following the thickness factor appropriate for the temperature at which the test was conducted and multiply by the time in seconds required to expose base metal as noted in 38.7.