PHe Level
The pHe value is a measure of acidity in ethanol. Work by the auto manufacturers and others have indicated that low pHe ethanol (in both E10 and E85 blends) can contribute to accelerated corrosion of certain fuel system parts of the automobile. While the ASTM standards limit total acidity, as acetic acid, to 0.007 mass percent (56 mg/L), this standard is not always sufficient to limit more aggressive sulfuric-based acids. Ethanol meeting the ASTM acidity standard may still be of low pHe. The ASTM has developed a test method to monitor "pHe." This test method measures acid strength and reports a pHe value. (Note: A pHe value is not directly comparable to pH values for water solutions). The ASTM pHe test method is designated and titled as "ASTM Designation: D6423 Standard Method for Determination of pHe of Ethanol, Denatured Fuel Ethanol, and Fuel Ethanol (Ed75-Ed-85)." As with the other ASTM standards, ASTM D6423 can be obtained from the ASTM.