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Lab Methods

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Silver Corrosion

  • Method ASTM D7667
  • Repeatability Not yet determined
  • Reproducibility Not yet determined
  • Blending non-linear
  • Additive Correction Yes

Sulfur compounds are found in crude petroleum, although most of these are removed during refining. However, of the sulfur compounds remaining in the petroleum product, some can have a corroding action on various metals and this corrosivity is not necessarily related directly to the total sulfur content. The effect can vary according to the chemical types of sulfur compounds present. The silver strip corrosion test is designed to assess the relative degree of corrosivity of a petroleum product.

This is very important because silver is used in the contacts points for fuel level sending units in the automotive industry. If a product corrodes this contact it will render the fuel sending unit useless and the vehicle will no longer correctly display the fuel level the car.

The method is performed by first polishing a silver strip to a finish of 240grit. The strip is then placed in a test tube filled with sample and placed into a metal pressure vessel (bomb). This bomb is sealed and placed into a heating bath maintained at 122°F for 2 hours. Once the specified time has elapsed the strip is removed, washed, and compared against the classification table that ranges from 0 (no tarnish) to 4 (blackening).