Ladislav Vrsalović

CORROSION INHIBITION OF CuNi10Fe ALLOY WITH PHENOLIC ACIDS

The purpose of this study was to investigate the efficiency of two phenolic acids, namely p-hydroxybenzoic acid (HBA) and protocatechuic acid (PCA), as corrosion inhibitors for CuNi10Fe alloy in a 0.5 mol dm−3 NaCl solution. In these investigations, open circuit potential measurements, potentiodynamic polarization measurements, and the linear polarization method have been used. It was found that both phenolic acids had similar corrosion inhibition effects on the CuNi10Fe alloy dissolution. The inhibition efficiency (IE) increased with increase in inhibitor concentration. The polarization shows that both compounds functioned as cathodic corrosion inhibitors by adsorption on the surface of CuNi10Fe alloy according to the Freundlich adsorption isotherm. The numerical values of free energies of adsorption indicate physical adsorption of the compounds on the electrode surface. DFT-based quantum chemical computations and molecular dynamics (MD) simulations revealed identical electronic and adsorption structures for both HBA and PCA, which could account for the similarities in the experimentally observed inhibiting effects.

Some new studies of sacrificial anodes

Aluminium and its alloys play an important role as anodic materials in sacrificial protection. Many well-known zinc sacrificial anodes are prone to passivation, which reduces their protective activity. For that reason it was necessary to find an anodic material in which the passive state of the protector has been disrupted. Such capabilities have been found with aluminium when a small quantity of an alloying element is added to it, making the ever-present protective oxide film porous and providing small resistance to anodic dissolution of aluminium. The contents of the alloying element in the total alloy mass prepared out of technical purity aluminium (99, 8%) and the alloying element must be as small as possible so as not to affect the basic properties of pure aluminium. Aluminium is the anode of choice for saltwater environments. The purpose of this study is to examine the effect of addition of small quantities of alloying element, which will not affect the basic advantages of aluminium, electrochemical properties and homogeneity of the alloy with the commercial name Akalpro. Due to high output current densities, the Akalpro electrodes are designed so that the outer surface is as small as possible. This is an advantage when protecting parts of objects (e.g. ships) where it is important to ensure protection with small masses of protector. Akalpro does not sparkle when hit, and does not release significant quantities of hydrogen, so that it can be used without danger as sacrificial anode in ballast tanks, for transportation of oil and inflammable liquids.

Development of a flow manifold for Fe(III) ion determination with a fluoride ion-selective electrode.

Continuous-flow (CF) and flow-injection (FI) analysis using the fluoride ion-selective electrode (FISE) as detector have been investigated. The measurements were performed in a home-made cell under appropriate flow conditions (2.86 or 3.45mlmin(-1), 0.2ml samples, 10(-6)M sodium fluoride). The calibration graph was obtained by plotting the signal height versus concentration of iron in the range of Fe(III) concentration from 10(-5) to 10(-1)M in acetate buffer (pH 2.8 or 3.4). In all described procedures, the range of linear response extends to the Fe(III) concentration from 1x10(-3) to 1x10(-1)M, with detection limit 9x10(-5)M. The effect of double-line, two-line flow manifold and CF was investigated and discussed.

Comparison of the corrosion behavior and surface morphology of NiTi alloy and stainless steels in sodium chloride solution

The corrosion behavior of NiTi alloy and stainless steels (AISI 316L and X2CrNiMoN22-5- 3) in 0.9% sodium chloride (0.154 mol/l) solution was investigated using open circuit potential measurements, potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Microstructural analyses before and after electrochemical tests were performed with the scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). The lowest corrosion current density has NiTi alloy and the extent of the passive range increased in the order AISI 316L stainless steel < NiTi alloy < X2CrNiMoN22-5-3 duplex stainless steel. The oxide film formed on all samples has a double-layer structure consisting of a barrier- type inner layer and a porous outer layer. Oxide films formed on the surface of steels mainly contains iron oxides and chromium oxide, while the surface film of the NiTi alloy mainly contains TiO2 oxide.

Corrosion Protection of Copper in Sodium Chloride Solution using Propolis

In this investigation the possibility of inhibiting corrosion of copper using ethanol extract of propolis in 0.5 mol dm-3 NaCl solution was investigat