scope:

This standard describes a procedure for the application of a coating system to the interior surfaces of new and used railroad steel tank cars used primarily in the transportation of concentrated (90 to 98%) sulfuric acid at ambient temperatures. The requirements for surface preparation, qualified inspection of the completed coating system, and testing by the use of adequate, readily available instruments are also covered in this standard.

For the purposes of this standard, the term concentrated sulfuric acid broadly refers to acid in the concentration range of 90 to 98%. Commercial sulfuric acid is usually handled at 93% concentration because its minimum freezing point is -34°C (-30°F). Sulfuric acid at 98% has the same high corrosiveness to carbon steel as 100% acid, and has a freezing point of approximately 7°C (45°F). All concentrations of sulfuric acid can contain impurities that can significantly alter its inherent corrosion characteristics.

In addition to adhering to the conditions set forth in this standard, tank cars hauling concentrated sulfuric acid must comply with U.S. DOT(footnote 1) and AAR(footnote 2) specifications² pertaining to DOT 111-A100-W2 tanks.

The minimum as-built wall thicknesses of metal surfaces to be coated in accordance with this standard should be 11.0 mm (0.43 in.).

Liquid coatings used in this standard may be hazardous and therefore basic safety precautions regarding the handling and application of these coating materials and solvents should be used. Chapter 1 of NACE TPC Publication No. 23 contains more detailed information. The material safety data sheet (MSDS) supplied by the coating manufacturer provides additional information relative to the coating and current government regulations.

This standard does not provide a full treatise on corrosion of steel by concentrated sulfuric acid; this is an extensive subject in its own right. Further information on this subject is published by NACE and other organizations.

Footnote 1 - U.S. Department of Transportation (DOT), 400 7th Street SW, Washington DC 20590.

Footnote 2 - Association of American Railroads (AAR), 50 F Street NW, Washington DC 20001-1564.