Experimental and theoretical assessment of benzopyran compounds as inhibitors to steel corrosion in aggressive acid solution

•Benzopyran derivatives exhibit high inhibition efficiency.•The polarization studies indicated that the two inhibitors acted as mixed-type inhibitors.•Ch-I and Ch-II molecules inhibited steel corrosion via physical and chemical adsorption.•Adsorption studies indicated that the inhibitors obeyed Langmuir isotherm.•Theoretical calculations further showing a definite correlation between the theoretical and experimental results.