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The electrochemical behaviour of linear alklybenzene sulfonate (LAS) on Pt electrodes was investigated in 0.05M Na2SO4 and in 0.1M NaCl at pH=8 by the potentiokinetic method and by electrolysis. The anodic and cathodic semilogarithmic current-potential curves were obtained between -1.6V - +1.6V. The experimental discharge potentials were determined by means of current-potential-curves obtained by electrolysis between 0-3V. The percentages of surface active material remaining in the solution after specified periods (0-6hrs) were determined for different initial concentrations of LAS (30, 150, 300 ppm) by using a potentiostat at +1.6V and by applying a potential of 20V via a direct current source. The concentrations of LAS in the solution were determined with a UV spectrophotometer. The results indicate that when a potential of 20V is applied on the electrodes the concentrations of surface active materials (LAS) decrease by 40-50% at the end of 6 hours in 0.05M Na2SO4 solution.

85 ÖZET Azotlu ve sülfürlü maddeler günümüzde geniş bir kul lanım alanı bulmakta ve bu maddelerin atıkları su, hava v© toprağın bileşimini bozmaktadır. Çevre kirleticisi diye ad landırdığımız bu atıkların, insan sağlığına etkileri geniş bir şekilde araştırılmaktadır. Ancak atıklar su, hava ve top rağa karışarak buralarda kullanılan yapı malzemelerini de etkileyerek korozyona neden olmaktadır. Endüstriyel tesisler de atıklarını verdikleri deniz ve nehir sularını, değişik amaçla tekrar kullanmak t ad ir. Bu durumda da tesislerde koroz- yon ortaya çıkmaktadır. Su, hava ve topraktan geçen boru hat ları v.b. ve endüstriyel tesislerin korozyonu, malzemenin kullanım ömrünün kısalmasına ve ekonomik kayıplara neden ol maktadır. Bu amaçla, demirin temiz ve NH4 S iyonlarıyla (C=10, -2-1 ' 10, 10 M) kirletilmiş yapay deniz suyundaki (pHz8, 6, 4) korozyon davranışları ', kütle kaybetme hızları1, korozyon po tansiyelleri (E ), polarizasyon dirençleri (R' ) ölçülerek ve akım-potansiyel eğrileri yardımıyla araştırılmıştır. Korozif etkisi zaten yeterince yüksek olan deniz su yuna iki kirletici (S, NHj ilavesi korozyon hızını daha ar tırırken, korozyon potansiyellerini daha aktif yapmakta, polarizasyon direncini düşürmekte ve sabit bir potansiyelde geçen akım yoğunluğunu artırmaktadır. Bu durumda, yapay deniz suyuna kirleticilerin (NH4, S) ilavesi demirin çözünme mekanizmasını değiştirmek tedir (bölüm 1.2.2). Bu çalışmada, CÎ ve S 'lü ortamlarda ay rı ayrı önerilen çözünme mekanizları bir araya getirilerek tartışılmış ve NH, iyonlarının etÜbfsi de dikkate alınarak yeni çözünme mekanizmaları önerilmiştir. 86 SUMMARY i Nowadays, there is a large application of nitrogen and sulfur compounds and these waste matters are spoiling the composition of water, air and soil. The enviromental pollution effect of these waste materials on human health has been investigat@d However, these wastes cause corrosion by mixing into water, air and soil and also by effecting the construe tion materials. Although the industry foundations discharge their waste water into rivers and the sea, they still use that polluted water back again for other purposes. As a result corrosion occurs. The corrosion in the pipelines passing through water, air and soil and industrial foundation results in shortening the life of these mateirals and caizse economic lostes. For this purpose, irons corrosion in clean and polluted synthetic sea water pH=8, 6, and 4, and of some ions S, NH4 -3 -9 -1 (C=10,10,10 M) have been investigated by weight loss, corrosion potential (E ), polarization resistance (R ) measurements and current-potential curves. While addition of two ions (S, NH*) to the sea water which already has high corrosive effect speeds up the corrosion rate besides it also makes the corrosion potential more active and reduces the polarization resistance and increases current density at constant potential. In this case, when the polluted ions (NH., S) are added into synthetic sea water the dissolution mechanizm of the iron has been changed (part 1.2.2). In this research work, the dissolution mechanizm of iron in CÎ and S containing media has been discussed separetely and together and new dissolution. mechanizms have been proposed taking NH. ions into consideration. 91

İskenderun Körfezi 'ndeki kirlilik derişimleri belirlenip, yapı malzemelerine korozif etkisi araştırılmıştır. Yapı Malzemelerinin korozyon davranışları kirlenme- »iş ve kükürtle kirlenmiş deniz suyunda incelenmiştir. Kükürt ve oksijenin deniz suyunda birlikte olması durumunda korozyon oranlarının yüksek olduğu saptanmıştır. VI.ABSTRACT The corrosive effect of pollutants on materials of construction, and the concentrations of these pollutants in İskenderun Bay has been investigated. The corrosion behavior of construction materials in unpolluted and sulphide- polluted seawater has been in vestigated. It is seen that the co-presence of sulphide ion and oxygen in seawater results in high corrosion rates. 61

Polyaniline (PANi) coating (~1.1 µm thick) was synthesized electrochemically on mild steel (MS), from 0.1 M aniline containing aqueous oxalic acid solution and using cyclic voltammetry technique. Then, this PANi coating was modified with the deposition of zinc particles from 0.2 M ZnSO4 solution. The electrodeposition of zinc particles (approximately 1 mg/cm2) has been achieved, at the constant potential value of -1.20 V. The corrosion performance of zinc modified PANi coating has been investigated in 3.5% NaCl solution, by using electrochemical impedance spectroscopy and anodic polarisation curves. Also, the corrosion behaviour of single PANi coated MS and bare zinc (Zn) samples have been investigated, for comparison. It was shown that zinc deposition lowered the permeability of polymer film significantly. Also, the zinc particles provided important cathodic protection to MS for considerably long immersion period. The polymer film provided the electrical conductivity between the substrate and zinc particles, this enhanced the cathodic protection efficiency. The corrosion of zinc particles led to formation of very stable corrosion products which improved the barrier property of zinc modified PANi coating system, further. © 2005 Elsevier B.V. All rights reserved.