New Test Method for Erosion of Coatings by Flowing Water Slurry
1. Scope
1. Scope 1.1 This test method provides a procedure for evaluating the erosion of polymeric materials, namely coatings, in a vigorously agitated water slurry. This procedure simulates the degradation caused by sand, silt, and other suspended sediments in raw (or untreated) water. Note 1The scrub resistance of paints can be evaluated by Test Methods D4213 and D2486. For the abrasion resistance of concrete materials, Test Method C1138 should be used. Test methods G32 and G134 should be used for cavitation erosion of a solid and Test Method G73 provides a general method for liquid impingement of a solid. 1.2 This test method is intended to carry out and isolate the erosion of polymeric materials, whether they are coatings, polymer composites, or otherwise. The polymer degradation results from a preferential erosion of the softer polymer matrix upon impingement of the harder sediments suspended in the water. Over time, the repeated mechanical defects result in large-scale erosion of the polymer matrix. Note 2Polymeric coatings often contain hard particulate matter such as ceramic, glass, or metal pigments as fillers and can be considered a composite with the softer polymer serving as the matrix. These coatings can be tested by this method; however, the size and shape of the fillers will have a significant effect on the erosion processes. 1.3 The erosion of a coating can be classified by several phases or periods. This is known as the cumulative erosion-time curve. First, an incubation period may be observed as the erodant impacts the polymer surface with little or no damage. This is most pronounced for elastomeric coatings which absorb the erodants energy with high efficiency. The acceleration period begins as the erosion rate begins to increase. This signifies the loss of the outermost polymer layers. A maximum rate period follows, marked by a high, constant erosion rate. In some cases, this is followed by a deceleration of the rate and a subsequent lower constant erosion rate. This is defined as the terminal period. Note 3Test Method G73 provides a detailed description of cumulative erosion-time curves. 1.4 The values stated in acceptable metric units are to be regarded as the standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Keywords
Power generation
Rationale
Bureau of Reclamation maintains hydro turbines. Standards for testing Coatings are needed. None exists at this time.
