In this paper, the electrochemical properties of high - purity aluminium with the addition of small amounts of gallium at high cathodic potentials have been investigated. The anodic current was followed through time in order to determine the quantity of charge needed for the formed substances oxidation. Anodic current responses for the period of 1 s were recorded. Time responses for the cathodic and anodic currents were recorded and showed in characteristic diagrams. The range of low and high cathodic potentials (LCP, HCP) was defined for all samples. For the experimental work, standard electrochemical cell with saturated calomel electrode (SCE) and platinum counter electrode were used. The solution 2 M NaF was used for this work.

Abstract The growth mechanism and electrochemical properties of an oxide film on AISI 304 grade stainless steel were studied in 0.01 and 0.1 mol L−1 fluoride solutions with different pH values (4.5, 5.5, 6.5) by means of electrochemical techniques. The anodic growth and stability of the oxide film on the stainless steel were characterized using cyclic voltammetry. Potentiodynamic analysis suggests that the oxide film growth occurs according to the high-field mechanism. Electric field strength, high-field growth exponential law constants, ionic conductivity through the film and half jump distance were determined. The electrochemical properties of the oxide film, formed spontaneously at the open circuit potential, were studied using electrochemical impedance spectroscopy. The results showed that the fluoride concentration has more considerable influence on the dissolution rate and the resistance of the oxide film than the pH.

Complex requirements for quality and competition on the market place are forcing manufactures to improve existing the aluminium alloys properties and develop new ones. Such streaming has been recently expressed in the food industry where are the numerous studies dedicated to down-gauging the aluminium foil required for flexible packaging laminates, while maintaining the same barrier and rigidity properties, by optimising package design. Final performances of packaging films do not depend only on mechanical but also on corrosion properties [1]. According to the European norm EN 573-3 the Fe content in Al-Fe-Mn (EN AW 8006) alloy may vary from 1.20 to 2.00 wt. %. The article gives the results of an investigation both of mechanical and corrosion properties of the cold rolled sheets of EN AW 8006 alloy with four different levels of Fe content. The alloys cold rolling process is performed under industrial conditions. The corrosion properties of Al-Fe-Mn (EN AW 8006) were studied in a 0.5 M NaCl solution at 25oC. The methods chosen for investigation of corrosion behaviour of Al-Fe-Mn (EN AW 8006) were: (a) potentiodynamic polarization (b) cyclic voltammetry and (c) electrochemical impedance spectroscopy. By tensile tests, elastic and plastic behaviour of investigated alloys under conditions of static uniaxial tensile stress, were determined. All tests were performed on cold rolled samples in the longitudinal direction of rolling (RD) and transverse to the direction of rolling (TD). The cold rolling of aluminium alloys generates the deformed layers on surface [2]. These deformed layers have a high electrochemical reactivity which affects on corrosion resistance. Tensile strength of cold rolled samples increases and elongation decreases with increasing degree of cold deformation. Results obtained from these investigations could be useful for industrial application.

Complex requirements for quality and competition on the market place are forcing manufactures to improve existing the aluminium alloys properties and develop new ones. Such streaming has been recently expressed in the food industry where are the numerous studies dedicated to down-gauging the aluminium foil required for flexible packaging laminates, while maintaining the same barrier and rigidity properties, by optimising package design. Final performances of packaging films do not depend only on mechanical but also on corrosion properties [1]. According to the European norm EN 573-3 the Fe content in Al-Fe-Mn (EN AW 8006) alloy may vary from 1.20 to 2.00 wt. %. The article gives the results of an investigation both of mechanical and corrosion properties of the cold rolled sheets of EN AW 8006 alloy with four different levels of Fe content. The alloys cold rolling process is performed under industrial conditions. The corrosion properties of Al-Fe-Mn (EN AW 8006) were studied in a 0.5 M NaCl solution at 25oC. The methods chosen for investigation of corrosion behaviour of Al-Fe-Mn (EN AW 8006) were: (a) potentiodynamic polarization (b) cyclic voltammetry and (c) electrochemical impedance spectroscopy. By tensile tests, elastic and plastic behaviour of investigated alloys under conditions of static uniaxial tensile stress, were determined. All tests were performed on cold rolled samples in the longitudinal direction of rolling (RD) and transverse to the direction of rolling (TD). The cold rolling of aluminium alloys generates the deformed layers on surface [2]. These deformed layers have a high electrochemical reactivity which affects on corrosion resistance. Tensile strength of cold rolled samples increases and elongation decreases with increasing degree of cold deformation. Results obtained from these investigations could be useful for industrial application.

Adsorption is one of the effective methods of advanced wastewater treatment, which industries employ to reduce hazardous organic and inorganic wastes in effluents. The use of low cost adsorbent has been investigated as a replacement for current costly methods of removing toxic substances from wastewater. In this article, the use of low cost adsorbents for the removal of toxic substances from wastewater has been reviewed.

The influence of the addition of small quantities gallium to high-purity aluminium on its electrochemical behaviour at high cathodic potentials (up to -2.0 V vs. SCE) was investigated using the potentiostatic pulse method. After cathodic polarization, anodic current was traced vs. time in order to determine the quantity of charge necessary for oxidation of substances formed. Anodic current responses to the return to the EOCP were also recorded in the period of 1 s. Time responses of the cathodic and anodic current were analyzed. The range of low and high cathodic potentials (LCP, HCP) was defined for all the samples. It has been established that the oxide film retains its properties in the LCP range, while in the HCP range cathodic breakdown and hydration of the oxide take place. Electrochemical methods complemented by SEM and EDAX analysis before and after the cathode pulse of -1.9 V vs. SCE.

Zbog vrlo siroke primjene i ekonomske važnosti aluminija i njegovih slitina sve veca pozornost usmjerava se njihovoj zastiti od korozije pomocu organskih inhibitora[1]. Međutim, veliki broj komercijalnih inhibitora koji se rabe u te svrhe je toksican, pa se u novije vrijeme ulažu napori da se isti zamjene prirodnim, netoksicnim supstancijama[2, 3, 4], ekoloski prihvatljivim. Slitina Al-2.5 Mg služi kao ambalažni materijal u prehrambenoj i farmaceutskoj industriji. U radu je ispitana mogucnost inhibicije korozije Al i Al-2.5 Mg slitine u w = 3 % NaCl otopini pri 25 oC pomocu prve kisele fenolne podfrakcije vodenog ekstrakta lisca ružmarina (Rosmarinus officinalis L.). Ispitivanje sastava ove podfrakcije pomocu visokotlacne tekucinske kromatografije na reverznoj fazi (HPLC-RP) potvrdilo je postojanje p-kumarinske kiseline u podfrakciji K1. Mjerenja su izvedena metodom potenciodinamicke polarizacije u podrucju koncentracije inhibitora (od 1 x 10-6 do 1 x 10-3 mol dm-3). Rezultati su pokazali da se ispitivane supstancije adsorbiraju na povrsini metala prema Freundlich-ovoj adsorpcijskoj izotermi, a dobivene vrijednosti standardne slobodne energije adsorpcije ukazuju na fizikalnu adsorpciju. Iz polarizacijskih krivulja, odnosno dobivenih elektrokemijskih velicina može se zakljuciti da p-kumarinska kiselina djeluje kao katodni tip inhibitora korozije.

The results presented in this paper were obtained with three Al-Ga binary alloys that had been prepared on super pure (99.999 %) Al base. The yield of hydrogen formed during cathodic polarisation of Al-Ga alloys in a neutral salt solution was measured volumetrically as a function of current density, temperature (between 20 and 80°C) and gallium content in the alloy (0.1, 0.26 and 2.6 wt. % Ga respectively). The yield of hydrogen was established to be about 2 or even less at all current densities and at low temperatures, while with increasing temperature it approached the value of 4. The yield of hydrogen decreases with the increase of gallium content in the alloy especially at lower temperatures.

Ako se legura aluminija uroni u deaeriranu otopinu alkalijskih halogenida korozijski potencijal se spontano uspostavlja u podrucju minimalne struje anodnog otapanja i brzine izlucivanja vodika. Pri promjeni potencijala u negativnom smjeru do neke kriticne vrijednosti dolazi do naglog povecanja kako brzine izlucivanja vodika, tako i otapanja metala, sto se pripisuje promjeni strukture oksidnog filma (hidratacija) koja znacajno smanjuje njegovu elektricnu otpornost. U ovom radu je ispitano ponasanje legure Al-Ga (sa sadržajem Ga 0.1, 0.2 i 2.60 %), pripremljene od tehnickog aluminija (99.8%), za vrijeme katodne polarizacije do visokih negativnih vrijednosti potencijala. Ispitivanja su izvedena potenciostatskom pulsnom metodom u 2M NaCl otopini, pri temperaturi od 25  0.1 oC. Snimljene su vremenske ovisnosti katodne gustoce struje o pulzirajucem elektrodnom potencijalu, od potencijala otvorenog strujnog kruga, EOCP, do –2000 mV prema ZKE i duljine trajanja pulsa od 1 s. Rezultati su pokazali da u relativno sirokom podrucju potencijala (sve do pojave hidratacije) oksidni film zadržava svoja svojstva. Promjene koje se desavaju u podrucju visokih katodnih potencijala ukazuju na hidrataciju oksida od međupovrsine na kojoj se izlucuje vodik, do povrsine samog metala. Pracena je i vremenska ovisnost anodnog strujnog odgovora po povratku potencijala na vrijednost blisku EOCP, pri cemu je dobivena složena eksponencijalna ovisnost. Za pretpostaviti je da ona u prvih nekoliko ms odražava nabijanje dvosloja zbog nagle promjene potencijala, a potom oksidaciju supstancija nastalih za vrijeme katodnog procesa, koje nisu difundirale dalje u otopinu i koje su nestabilne na pozitivnijim potencijalima.

U radu je ispitana mogucnost inhibicije korozije Al-2.5Mg legure u 3% NaCl otopini pri 25C pomocu trece kisele fenolne podfrakcije vodenog ekstrakta lisca ruzmarina. Mjerenja su izvedena metodom potenciodinamicke polarizacije u sirokom podrucju koncentracije aditiva ( od 110-6 do 1 10-3 mol dm-3 ). Rezultati su pokazali da se ispitivane supstancije adsorbiraju na povrsini legure prema Freundlichovoj adsorpcijskoj izotermi, a dobivene vrijednosti standardne slobodne energije adsorpcije ukazuju na fizikalnu adsorpciju. Iz polarizacijskih krivulja može se zakljuciti da treca kisela fenolna podfrakcija djeluje kao katodni tip inhibitora korozije. Ispitivanja sastava ove podfrakcije pomocu visokotlacne tekucinske kromatografije na reverznoj fazi (HPLC – RP) potvrdila su prisutnost ferulicne kiseline u podfrakciji, a provedena potenciodinamicka mjerenja sugeriraju da je ferulicna kiselina odgovorna za inhibicijsko djelovanje trece fenolne podfrakcije navedenog ekstrakta ruzmarina.

Na vođenje procesa elektrolize aluminija u elektrolitickim celijama utjecu razliciti faktori. Među njima znacajno mjesto zauzima emisija stetnih tvari, a posebice ukupnog fluora. Imajuci u vidu težnju da se maksimalno zastiti okolis, moramo proces elektrolize aluminija, pri njegovom optimiranju promatrati i iz tog aspekta. Pokazatelj koji nam izravno govori o kvaliteti vođenja procesa je bilanca fluora. Iz tog razloga je težiste ovog rada upravo na toj bilanci i njenom određivanju. U visegodisnjem vremenskom razdoblju kontinuirano su mjereni podaci emisije i imisije fluornih spojeva iz celija, prociscivaca te u zraku u sali elektrolize i okolisu. Na taj nacin je kontroliran i utjecaj emisije na biljni i životinjski svijet. U cilju iskazivanja efikasnosti rada prociscivaca plinova postavljena je bilanca fluornih proizvoda na temelju rezultata dobivenih mjerenjem u tijeku rada elektrolize. Bilanca fluornih proizvoda provedena je pomocu razvijenog racunalnog programa koji sadrži dva bloka bilancnih jednadžbi koje se odnose na postupke mokre i suhe obrade. Postavljene jednadžbe su povezane preko efikasnosti rada poklopaca i emisije fluora u okolis. Razvijeni program omogucuje bržu i efikasniju obradu ulaznih podataka dajuci pregled svih parametara koji diktiraju ekoloski standardi. Na temelju toga može se dosta brzo reagirati, u slucaju potrebe , na odvijanje procesa elektrolize i voditi ga optimalno. Rezultati dobiveni proracunima pokazuju da je vrijednost emisije iz obrade plinova uglavnom zadovoljavala ekoloske standarde koje je propisao UNEP. Konkretno emisija fluora u okolis je iznosila od 0.49 do 0,79 kg F / t Al, a standard propisuje 0.75-1.1 kg F / t Al.