abrasion vs eating away

abrasion and eating away both are nouns.

Word	Noun	Adjective	Verb	Adverb
abrasion	Yes	No	No	No
eating away	Yes	No	No	No

As nouns, eating away is a hypernym of abrasion; that is, eating away is a word with a broader meaning than abrasion:

abrasion: erosion by friction
eating away: (geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively

Other hypernyms of abrasion include eroding, erosion, wearing, wearing away.

abrasion (noun)	eating away (noun)
the wearing down of rock particles by friction due to water or wind or ice	(geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively
erosion by friction
an abraded area where the skin is torn or worn off