Carbonic acid does not forms acidic salt.
Carbonic acid is a carbon-containing compound which has the chemical formula H2CO3. Solutions of carbon dioxide in water contain small amounts of this compound. It does not form acidic salts because it is a weak acid. H2CO3 is a weak acid that dissociates into a proton (H+ cation) and a bicarbonate ion (HCO3- anion). This compound only partly dissociates in aqueous solutions.