Experimental and computational studies of naphthyridine derivatives as corrosion inhibitor for N80 steel in 15% hydrochloric acid

•N80 steel protection by naphthyridine derivatives in 15% HCl.•Polarization results indicate that all the studied inhibitors are mixed-type but predominantly cathodic.•The SEM showed the smooth surface of N80 steel in the presence of ANCs.•Quantum chemical calculations provide good support to experimental results.

The inhibition effect of three naphthyridine derivatives namely 2-amino-4-(4-methoxyphenyl)-1,8-naphthyridine-3-carbonitrile (ANC-1), 2-amino-4-(4-methylphenyl)-1,8-naphthyridine-3-carbonitrile (ANC-2) and 2-amino-4-(3-nitrophenyl)-1,8-naphthyridine-3-carbonitrile (ANC-3) as corrosion inhibitors for N80 steel in 15% HCl by using gravimetric, electrochemical techniques (EIS and potentiodynamic polarization), SEM, EDX and quantum chemical calculation. The order of inhibition efficiency is ANC-1>ANC-2>ANC-3. Potentiodynamic polarization reveals that these inhibitors are mixed type with predominant cathodic control. Studied inhibitors obey the Langmuir adsorption isotherm. The quantum calculation is in good agreement with experimental results.