Agreed.But doing both at a time would leave you unable to determine the individual effects. If acid alone didnt affect the edge a second experiment could be cutting some fixed material (such as rope as you said) both with and without the acid. But the wear from the rope may overwhelm the effect of corrosion.
I guess you'd have to have 3 arms: acid only, abrasion only and acid plus abrasion in order to tease out the differences.