H. Saricimen

Initial stages of atmospheric corrosion of steel in the Arabian Gulf

Abstract Energy dispersive X-ray micro-analysis, X-ray diffraction and fluorescence, Auger, X-ray photo-electron spectroscopy and Fourier transform infrared spectroscopy have been used to characterise corrosion products on carbon steel after atmospheric exposure for periods up to 12 months to an industrial environment near the west coast of the Arabian Gulf. The results indicate that atmospheric corrosion starts by the formation of small blisters at discrete locations on the metal surface, presumably the anodic sites. The blister covers are very rich in iron chlorides and contain iron oxyhydroxides, oxides, sulphates and possibly hydroxide. The formation of iron chlorides as the primary corrosion product is only limited to the early stages of blister formation due to the aggressive nature of chloride ions. Chloride formation during later stages may be partially impaired since it requires the inward transport of fresh chloride ions through the then thick rust layer. In contrast, the formation of iron sulphates at the rust-metal interface continues by the acid regeneration mechanism (which leads to the electrochemical mechanism); therefore it is less dependent on the supply of fresh sulphate ions from the surface electrolyte through the growing rust layer.

Effect of waterproofing coatings on steel reinforcement corrosion and physical properties of concrete

Abstract This paper reports the results of a study conducted to evaluate steel reinforcement corrosion and some physical properties of concrete specimens coated with two polymer-based, a cement-based polymer-modified, and a cement-based waterproofing coatings. The coated and uncoated concrete specimens were subjected to accelerated corrosion to determine the time-to- corrosion initiation. The physical properties were also evaluated by subjecting the concrete specimens to wetting/drying cycles and heating/cooling cycles for five months. The physical properties evaluated were water absorption, water permeability, chloride permeability, and adhesion. The accelerated corrosion test results clearly showed that the specimens coated with the polyurethane elastomer-based waterproofing material performed better than concrete specimens coated with other waterproofing materials. This was followed by the specimens coated with cement-based polymer modified, epoxy-based, and cement-based coatings in descending order. The two polymer-based coatings showed better performance than the cement-based polymer-modified and cement-based coatings in terms of the evaluated physical properties.

The inhibition action of 1(benzyl)1-H-4-5-dibenzoyl-1,2,3-triazole on mild steel in hydrochloric acid media

Abstract The recently synthesized compound 1(benzyl)1-H-4,5- dibenzoyl-1,2,3-triazole (BDBT) possesses a considerable number of aromatic systems. A significant number of electrons are available on the three nitrogen atoms of the triazole ring. The inhibition effect of BDBT on the corrosion activity of mild steel in acid media has been investigated. Tafel polarization technique, AC impedance measurements and continuous linear polarization resistance method were employed in conjunction with a rotating cylinder electrode apparatus. The corrosion rate of mild steel in 1 % HCl was reduced by more than 95% in the presence of 50 ppm of BDBT. The BDBT has a mixed inhibition effect with a significant shift in the free corrosion potential to the cathodic direction. Film persistency tests showed that BDBT forms a stable film on the surface of the electrode.

Effectiveness of concrete inhibitors in retarding rebar corrosion

Abstract The effect of inhibitors on the corrosion of steel reinforcements in concrete was evaluated by using anodic polarization, electron spectroscopy for chemical analysis (ESCA) and Auger electron spectroscopy (AES). The reinforcement corrosion in uncontaminated concrete specimens was evaluated by impressing +4 V anodic potential for accelerated corrosion of the steel bar and measuring the time-to-cracking of the concrete specimens. The effectiveness of the inhibitors in retarding reinforcement corrosion in the contaminated concrete specimens was evaluated by measuring the corrosion potentials and corrosion–current density. Results indicated that the time-to-cracking in uncontaminated concrete specimens incorporating inhibitors M2 and R2 was higher than that in the control concrete specimens. While the increase in the time-to-cracking in the concrete specimens incorporating M2 was marginal, a significant improvement in the corrosion-resisting characteristics of concrete incorporating R2 was indicated over the control specimens. The data on time-to-cracking in the uncontaminated concrete specimens and the corrosion rate of steel in the contaminated concrete specimens indicated the usefulness of corrosion inhibitor R2 in retarding reinforcement corrosion. The electrochemical test results and surface analysis results using ESCA and AES techniques showed the better performance of inhibitor R2 compared to inhibitor M2 in retarding corrosion of steel in an environment of saturated calcium hydroxide in the presence of chloride ions.

Influence of atmospheric corrosion on the mechanical properties of reinforcing steel

Abstract This paper reports the results of an investigation carried out to evaluate the mechanisms of atmospheric corrosion of reinforcing steel in arid regions, and their influence on the weight loss, strength, elongation and bendability. The results indicated that atmospheric corrosion begins as a localized attack at discrete points on the metal surface. Upon extended exposure to the atmosphere, this localized attack gradually becomes a uniform form of attack covering the entire metal surface. Further, the atmospheric corrosion did not influence the strength and ductility of the steel.

Durability of proprietary cementitious materials for use in wastewater transport systems

Abstract Several methods and materials, such as high performance coatings, fiber glass reinforced linings, special mortars, brick or ceramic linings, etc., are used to protect concrete from sulfuric acid attack in a sewage environment. Two proprietary high alumina cementitious lining materials, CC and SC, are recent additions to the list of protective materials used in the Arabian Gulf. This paper documents the findings of a laboratory study under accelerated conditions as well as a two-year field study of CC and SC in a wastewater lift station in Jubail, Saudi Arabia. In the laboratory investigations, 50 mm cube mortar specimens prepared using: (1) SC, (2) CC, (3) Type I+8% silica fume cement, (4) Type I+20% fly ash cement and (5) Type I cement were exposed to 2% sulfuric acid for 150 days. The laboratory specimens were tested for weight reduction, compressive strength, sulfate content, and alkalinity. In the field, the walls and ceiling of a wastewater manhole were coated using the proprietary lining materials, SC and CC, and were exposed to a normal sewage service environment. Performance of the liner materials was monitored for sulfate content and alkalinity after 6, 12 and 24 months of exposure. The analysis and evaluation test data generated from the accelerated laboratory study and the field study, which lasted for 24 months, showed that SC performed better than other materials tested in this investigation.

Corrosion of reinforcing steel in concrete containing slag or pozzolans

Use of fly ash, silica fume, natural pozzolans, and blast-furnace slag in concrete is becoming increasingly common. Incorporation of these materials improves the durability of concrete. But as yet there are few quantitative data available on the effect of these materials on long-term corrosion of steel reinforcement. Such data will help the concrete technologists to select the proper type of materials to produce dense and impermeable concrete to withstand aggressive service environments. In this investigation, the long-term corrosion-resisting characteristics of concretes made with two fly ashes, a natural pozzolan, a blast-furnace slag cement, and a preblended portland-fly ash cement were evaluated. Specimens were immersed in 5% sodium chloride solution for a period of more than five years, and the corrosion activity was evaluated by monitoring the half-cell potentials and measuring the corrosion rate of embedded steel using linear polarization resistance technique. Results indicate that addition of pozzolans or slag increases the corrosion-resisting characteristics of concrete. The corrosion rate of steel in concrete made with blast-furnace slag cement is lower than in other concretes.

Effect of inhibitor treatment on corrosion of steel in a salt solution

This study examined experimentally different chemicals for inhibition of steel corrosion in a simulated aqueous solution for the industrial marine atmosphere of the Arabian Gulf region. The literature reported various inhibitors that can help in protection against metal corrosion in aqueous environments. Among them, 10 inhibitors (calcium silicate, cyclohexylamine, n-methylcyclohexylamine, dicyclohexylamine nitrite, sodium benzoate, sodium nitrate, sodium nitrite, sodium phosphate, sodium dihydrogen orthophosphate, and magnesium nitrate hexahydrate) were obtained and corrosion resistance of inhibitor applied steel specimens were examined in the simulated solution (2 wt.% NaCl and 1 wt.% Na2SO4). Test specimens were prepared from locally produced reinforcing steel products. Treatment of steel with either dicyclohexylamine nitrite or sodium dihydrogen orthophosphate both at 10 mM concentration for 1 day at room temperature resulted in significant inhibition of corrosion. No significant improvement in corrosion inhibition was observed either with an increase in inhibitor concentration at room temperature or with an increase in inhibitor application temperature at 10 mM concentration. A further study is planned to examine the inhibition performances of the two inhibitors under actual atmospheric conditions in the Arabian Gulf region (industrial marine environment).

Effect of rebar cleanliness and repair materials on reinforcement corrosion and flexural strength of repaired concrete beams

Abstract This paper presents result of a study conducted to evaluate the effect of two rebar cleaning procedures and repair materials on reinforcement corrosion and flexural strength of repaired concrete beams. The steel bars in the reinforced concrete beams were corroded to varying degrees to simulate field situations and then repaired utilizing two different cleaning techniques and two repair materials. The repaired beams were then tested in flexure to evaluate the effect of cleaning method and repair materials on the corrosion-resistance and flexural capacity of repaired beams. The electrochemical behavior of cleaned and corroded steel bars was evaluated by conducting a DC potentiodynamic scan. The data indicated an insignificant change in the flexural strength of repaired beams regardless of the cleaning techniques or the repair materials. The accelerated corrosion data indicated lowest corrosion rate in the concrete specimens repaired with polymer-modified cement mortar after cleaning the bars by sand blasting (SB). The DC polarization data indicated the formation of a stable passive film on the steel bars cleaned by SB compared to uncleaned bars and those cleaned by wire brush.

Effect of field and laboratory curing on the durability characteristics of plain and pozzolan concretes

Abstract The environmental conditions in the Arabian Gulf countries are classified as aggressive and severely corrosive. Field and laboratory studies have shown that concrete in this region should be designed not only for strength but also for durability. Utmost emphasis should be given to produce dense and impermeable concrete, to extend the service life of structures. In this study, concrete samples were prepared using various types of cements and fly ashes at various mix designs. The samples were cured in the field and in laboratory conditions. The permeability was determined by volume of permeable voids and absorption tests. The results showed that continuous water curing is necessary to obtain the least permeable concrete for both plain and pozzolan concretes. Irrespective of curing procedure followed, the fly ash concrete exhibited lower permeability than plain concrete for an initial test period of 7 days during curing. The fly ash concrete samples cured in the laboratory exhibited lower initial surface absorption than control concretes after 90 days of curing for all fly ash additions (10–40%) and cement factors (275–450 kg/m3) used.