WHY ? : Abrasion and erosion mechanisms are quite different from each other, and can lead to very different material behaviour.  For instance, a hard and brittle surface may be very resistant to abrasion, but sensitive to erosion under 90° impact. 

HOW ? : Using two separate test systems :

- ASTM G65 describes the method to rub solid particles tangentially over a material.  'Dry sand rubber wheel abrasion'.  ASTM G75 uses a similar motion, but reciprocating and in a wet slurry.  But it's still abrasion.

- ASTM G76 on the contrary describes how to impact with a gas flow carried stream of particles on a surface under varying angles, between 90° perpendicular impact and 15°.

RESULT : ductile vs. brittle materials behave very differently, depending on the impact angle of particles, and by extension, depending on whether it's abrasive vs. erosive conditions.

Afbeeldingsresultaat voor erosion ductile brittle