THE USE OF CORROSION INHIBITOR IS ONE OF THE MOST EFFECTIVE MEASURES FOR PROTECTING METAL SURFACES AGAINST CORROSION IN ACID ENVIRONMENTS. THE CORROSION OF IRON AND Mild steel (MS) IS A FUNDAMENTAL ACADEMIC AND INDUSTRIAL CONCERN THAT HAS RECEIVED A CONSIDERABLE AMOUNT OF ATTENTION. TO CONTROL CORROSION, ORGANIC INHIBITORS ARE USED TO PROTECT THE METAL FROM CORROSION BY FORMING A BARRIER FILM ON THE METAL SURFACE [1]. ORGANIC COMPOUNDS CONTAININGELECTRONEGATIVE FUNCTIONAL GROUPS AND P-ELECTRONS IN CONJUGATED DOUBLE OR TRIPLE BONDS GENERALLY EXHIBIT GOOD INHIBITIVE PROPERTIES BY SUPPLYING ELECTRONS VIA P ORBITALS. SPECIFIC INTERACTION BETWEEN FUNCTIONAL GROUPS AND THE METAL SURFACE AND HETEROATOMS LIKE N, O, AND S PLAY AN IMPORTANT ROLE IN INHIBITION DUE TO THE FREE ELECTRON PAIRS WHICH THEY POSSESS [2]. WHEN BOTH OF THESE FEATURES COMBINE, INCREASED INHIBITION CAN BE OBSERVED THE AIM OF THIS WORK IS TO INVESTIGATE THE INHIBITING INFLUENCE OF HYDROGEL ON Mild steel CORROSION IN 1.0M HYDROCHLORIC ACID SOLUTION. THIS HAS BEEN STUDIED BY POTENTIODYNAMIC POLARIZATION AND ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS) TECHNIQUES. TESTS WERE CONDUCTED IN 1.0M HCL SOLUTION WITH DIFFERENT CONCENTRATIONS OF INHIBITOR. ELECTROCHEMICALEXPERIMENTS WERE CARRIED OUT USING AN AUTOLAB (PGSTAT 12). A THREEELECTRODEARRANGEMENTWAS USED FOR ELECTROCHEMICAL STUDIES. WORKINGELECTRODEWAS PREPAREDFROM A Mild steel SHEET, MOUNTED IN POLYESTER SO THAT THE AREA EXPOSED TO CORROSIVESOLUTION WAS 1CM2. A SATURATED CALOMEL ELECTRODE (SCE) AND GRAPHITE RODWERE USED AS THE REFERENCE AND COUNTER ELECTRODES, RESPECTIVELY. POTENTIODYNAMIC POLARIZATION CURVES WERE OBTAINED WITH A SCAN RATE OF 0.5 MV S-1 IN THE POTENTIAL RANGE FROM -150 TO+150 MV RELATIVE TO THE CORROSION POTENTIAL.CORROSION CURRENT DENSITY VALUESWERE OBTAINED BY TAFEL EXTRAPOLATION METHOD. THE IMMERSION TIME BEFORE EACHMEASUREMENTWAS 60 MIN TO ACCESS AN EQUILIBRIUMPOTENTIAL. THE IMPEDANCE MEASUREMENTS WERE CARRIED OUT AT THE OPEN CIRCUIT POTENTIAL (EOCP) AND FRA SOFTWARE. THE ALTERNATING CURRENT FREQUENCY RANGE WAS EXTENDED FROM 100 KHZ TO 0.1 HZ WITH A SIGNAL AMPLITUDE PERTURBATION OF 5 MV. THE CORROSION PARAMETERS AS WELL AS INHIBITION EFFICIENCIES WERE OBTAINED FOR DIFFERENT CONCENTRATIONS OF INHIBITOR. THE INHIBITION EFFICIENCIES SHOWED THAT THE HYDROGEL ACTS AS A GOOD CORROSION INHIBITOR FOR Mild steel IN HYDROCHLORIC ACID. THE INHIBITION EFFICIENCY SLIGHTLY DECREASED IN THE TEMPERATURERANGE 30-60OC. HYDROGEL IS A MIXED SAFE CORROSION INHIBITOR FOR CARBON steel IN MEDIUM ACID SOLUTIONS THAT ACTS BOTH OVER THE CATHODIC PROCESS OF HYDROGEN EVOLUTION AND THE ANODIC PROCESS OF METAL DISSOLUTION. THERMODYNAMIC ADSORPTION AND ACTIVATION PARAMETERS WERE DISCUSSED. ADSORPTION OF THE SYNTHESIZED INHIBITOR WAS FOUND TO FOLLOW THE LANGMUIR ADSORPTION ISOTHERM.

EPOXY BASED HYBRID ORGANIC-INORGANIC PROTECTIVE COATINGS WERE DEVELOPED FOR THEIR CORROSION BEHAVIOR OF A STAINLESS steel SUBSTRATE. THE ANTICORROSION PROPERTIES OF THE HYBRID COATINGS, WHICH IMMERSED IN 5 WT.% NACL SOLUTION, WERE EVALUATED BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS). THE EIS RESULTS SHOWED THAT THE CORROSION PROTECTIONS OF THE HYBRID COATINGS REDUCED WITH INCREASING OF THE IMMERSION TIME BECAUSE THE BARRIER MECHANISM OF THESE COATINGS CHANGED WITH INCREASING THE IMMERSION TIME. THE EQUIVALENT CIRCUITS USED FOR NUMERICAL FITTING OF THE EIS DATA OF THE HYBRID COATINGS AND ATTRIBUTED CORROSION PROTECTION MECHANISMS WERE PRESENTED AT THIS ARTICLE.

QUANTUM CHEMICAL APPROACH AT B3LYP/6-31++G (D, P) LEVEL OF THEORY WAS USED TO CALCULATE SOME ELECTRONIC PROPERTIES OF AZO DYE DERIVATIVES, AS Mild steel CORROSION INHIBITORS, TO AS CERTAIN THE CORRELATION BETWEEN THEIR INHIBITIVE EFFICIENCIES AND SOME OF THE COMPUTED PARAMETERS. CALCULATIONS OF PREPARED COMPOUNDS GAVE USEFUL INFORMATION TO PREDICT THE INTERACTION BETWEEN THE SURFACE OF METAL AND THE ORGANIC MOLECULES AS CORROSION INHIBITORS.