corroboratory vs collateral

corroboratory is not a noun while collateral is a noun.

Word	Noun	Adjective	Verb	Adverb
corroboratory	No	Yes	No	No
collateral	Yes	Yes	No	No

As adjectives, corroboratory and collateral are synonyms defined as:

corroboratory (noun)	collateral (noun)
	a security pledged for the repayment of a loan

corroboratory (adjective)	collateral (adjective)
serving to support or corroborate	descended from a common ancestor but through different lines
	situated or running side by side
	additional but secondary; auxiliary;
	occurring with or following as a consequence
	serving to support or corroborate