Carbon dots from pomegranate-peel waste (PPCDs) and their N-doped counterparts (N-PPCDs) were hydrothermally synthesized and tested as corrosion inhibitors for carbon steel in 5 wt % HCl. Electrochemical (PDP, LPR, EIS) and weight-loss measurements, supported by surface imaging (SEM, AFM, and optical profilometry), showed inhibition efficiencies rising with concentration and peaking at 200 ppm. At this dose, PDP gave 70 % IE for PPCDs and 80 % for N-PPCDs; Rp increased from 52 Ω cm² (blank) to 151 Ω cm² (PPCDs) and 217 Ω cm² (N-PPCDs). N-PPCDs left the steel far smoother (Ra = 1.1 nm) than either PPCDs (2.4 nm) or the uninhibited surface (68 nm). Nitrogen doping enhanced adsorption and electron donation, making N-PPCDs a highly effective, sustainable corrosion inhibitor for acidic environments.