Characterization of steel surface under cathodic ... - IngentaConnect

Characterization of steel surface under cathodic protection in seawater Mariela Rendoń Belmonte Institute of Engineering, University of Baja California, Mexicali, Me´xico

Jose´ Trinidad Pe´rez Quiroz Materials Laboratory, Mexican Institute of Transport, Quere´taro, Me´xico

Benjamıń Valdez Salas Institute of Engineering, University of Baja California, Mexicali, Me´xico

Miguel Martıńez Madrid and Andre´s Torres Acosta Materials Laboratory, Mexican Institute of Transport, Quere´taro, Me´xico

Jesu´s Porcayo Calderoń Electrical Research Institute, Cuernavaca, Me´xico, and

Miguel Schorr Wiener Institute of Engineering, University of Baja California, Mexicali, Me´xico Abstract Purpose – The purpose of this paper is to characterize the surface of steel under cathodic protection while submerged in seawater, to understand the mechanism that controls the operation of the protection system. Design/methodology/approach – Steel rods were immersed in seawater and NaCl solution with applied cathodic protection. The experimental methodology included monitoring of corrosion potential (Ecorr), galvanic current (Igalv) protection potential (Eprotection) and the depolarization potential of steel during the time of exposure. In addition, the chemical composition of the steel surface was assessed using a Scanning Electron Microscope (SEM). Findings – In this research it was determined that the effectiveness of the CP system was mainly attributable to the formation of an iron oxide film on the steel surface. Research limitations/implications – It is necessary to carry out analysis of the chemical composition of deposits formed on the steel surface, perhaps using X-ray diffraction (XRD), to verify the presence of a protective oxide. Practical implications – Deposits on the steel surface have the beneficial effect of reducing the current required for efficient protection. Deposit formation therefore is of economic interest, as it decreases the cost of protection. Originality/value – A unique feature of cathodic protection in seawater is the formation of calcareous deposits on metal surfaces. Advantageous aspects of these deposits, such as decrease in cathodic current requirement, have been investigated by various authors from various viewpoints. However, very little attention has been paid to the impact of any iron corrosion product films; the present paper contributes useful understanding and explains the importance of the mechanism that controls the operation of the protection system. Keywords Steel, Cathodic protection, Films (states of matter), Seawater, Steel rods, Galvanic current, Surface properties of materials Paper type Research paper

rate of metal is significantly reduced.” However, this definition still fails to provide information regarding the nature and role of the metal/electrolyte interface, or the influence of surface films that form at this interface during the CP process (Leeds and Cottis, 2004). When applying CP for the first time to a structure, it is well known that a higher current and more negative structure/ electrolyte potential than the original open circuit potential (OCP) is observed. Over a period of a week or more after the CP is connected, the current decreases and the potential becomes more negative than the initial value (i.e. the potential value just minutes after the anode is connected to the structure) until it

1. Introduction Cathodic protection (CP) has been used as an effective technique to prevent corrosion of metallic structures in the oil, gas and marine industries, (Rousseau et al., 2010; NCHRP SYNTHESIS 398, 2009; Miyata and Wakabayshi, 2006; Kim and Scantlebury, 2004). CP is defined as “electrochemical protection achieved by decreasing the structure potential to a level whereby the corrosion The current issue and full text archive of this journal is available at www.emeraldinsight.com/0003-5599.htm

Mariela Rendoń Belmonte acknowledges the support of CONACYT for a scholarship. The authors acknowledge UABC (Universidad Autono´ma de Baja California) and Instituto Mexicano del Transporte (IMT) for allowing the experimental part of the research to be carried out in their facilities.

Anti-Corrosion Methods and Materials 60/3 (2013) 160– 167 q Emerald Group Publishing Limited [ISSN 0003-5599] [DOI 10.1108/00035591311315418]

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Characterization of steel surface under cathodic protection

Anti-Corrosion Methods and Materials

Mariela Rendoń Belmonte et al.

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reaches a stable value determined by the applied protection. In order to understand CP and the nature of the reinforcement “passivity,” it is important to know what is actually happening electrochemically at the surface when CP is applied. It has been reported that the application of cathodic current leads to the formation of deposits on the protected steel surface. In seawater, the cathodic currents induce dissolved oxygen (DO) reduction, which generate hydroxyl ions at the very near polarized surface, which increase the interfacial pH and result in enhanced carbonate ions concentration, precipitating an inorganic layer whose principal component is the calcium carbonate, perhaps containing some magnesium. Depending on the potential, magnesium hydroxide also can precipitate. This mixed deposit is generally called “calcareous deposit”. The importance of the deposit layer is widely recognized as playing an important part in controlling the corrosion of ferrous structures in seawater. It has been reported that calcareous deposits are able to protect ferrous structures exposed to seawater for tens of years, even after failure of the CP (Kenichi and Isamu, 2003). In view of the important role the calcareous film plays in protecting ferrous structures from corrosion, a large number of parameters, such as: applied potential, substrate nature, flow rate, temperature, pH, and the physicochemical parameters of natural seawater, have given rise to many researches for several decades (Yang et al., 2012). Leeds reported that films were formed as a direct result of cathodically polarizing metal specimens and that they were magnetite and not calcareous deposit (Leeds and Cottis, 2004). The aim of this research was to characterize the surface steel with CP while submerged in seawater to understand the mechanism that controls the operation of the protection system. Also, for comparison purposes, steel rods were immersed in NaCl solution to eliminate possible interference by calcareous deposits.

2.2 Potential and current measurements The monitoring period for all of the specimens was 230 days. Corrosion potential (Ecorr) was measured according to ASTM C876. The protection potential (Eprotection) and the depolarization potential of steel (Einstantoff, Eafter4 h, Eafter24 h) were measured according to standards NACE RP0285 and TM0101, as also were galvanic currents between anode and cathode. The reference electrode used in all measurements was a saturated calomel electrode (SCE) placed inside the chamber when performing the measurements. The criterion for efficient CP was the 100 mV standard established by NACE RP 0285 and TM 0101. 2.3 SEM and EDS examination The morphological and chemical composition of the steel rods surface exposed in seawater were analyzed using a scanning electron microscope (SEM) and electron dispersed spectroscopy (EDS).

3. Results 3.1 Corrosion potential The Ecorr values of the blank steel rods (B1-B6) after 20 days immersion varied , 2 750 mV vs SCE for both electrolytes, see Figure 2. The potential values of the specimens indicated corrosion problems according to ASTM C876. 3.2 Protection potential The potential values of steel rods P1-P6 within the first seven days of immersion indicated corrosion problems, but afterwards a potential shift in the negative direction was obtained due to its interaction with the sacrificial anodes. The displacement of potential from the OCP value was , 250 mV in the negative direction in all cases (P1-P6) (recorded values were about Eprotection of 2 1,050 mV vs SCE). This value remained constant during the rest of the monitoring period (Figure 3).

2. Experimental conditions

3.3 Steel potential depolarization Depolarization measurements for the six protected specimens in (P1-P6) were performed after 58, 118 and 205 days after anode/ rebar connection. The results are shown in Table I. All pairs (rebar/anode) match the 100 mV criterion established by NACE RP 0285 and TM 0101. The potential difference between the “instant off” value and the potential values obtained after 4 and 24 h was more positive than 100 mV. However, although all of the CP systems were effective, the steel rods immersed in seawater showed increased polarization compared to those immersed in the NaCl solution, and this difference was attributed to the chemical composition of the electrolyte.

Electrochemical corrosion tests were conducted following the practices and recommendations of ASTM standards G-3, G-52, C-876 and NACE standards RP 0285 and TM 0101 (ASTM G3, 2010; ASTM G52, 2011; ASTM C876, 2009NACE Standard RP0285, 2002; NACE Standard TM0101, 2001). 2.1 Specimen preparation Twelve steel rods (rebars) (ASTM A496, 2001), 17 cm long and 0.9 cm diameter, were arranged in four acrylic electrochemical cells, see Figure 1. The steel surfaces were cleaned and degreased in acetone and rinsed with distilled water. Two cells were filled with seawater and the rest with 3.5% sodium chloride (NaCl) to eliminate the possible influence of calcareous deposit. Six steel rods were immersed in each electrolyte. After seven days immersion, the rebars identified as P1-P3 in seawater and P4-P6 in NaCl solution were connected to sacrificial anodes (zinc wire) in order to provide a CP protection to the steel. The anode/cathode area ratio was 1:1. Both metals were individually connected, outside the acrylic cells, to facilitate the monitoring of depolarization and galvanic currents. The six remaining rebars; identified as B1-B3 in seawater and B4-B6 in NaCl solution were not cathodically protected and were used as blanks in the respective electrolytes.

3.4 Current densities Current densities were measured between the zinc anode and the protected steel rods (P1-P6), see Figure 4. The galvanic current decreased continuously until day 120, with values close to , 1 mA/m2 for the seawater, while for NaCl solution the current galvanic decreased until values close to , 2 mA/m2. Afterwards, these values were almost constant (Figure 4). At the end of the experiments the specimens polarized in the seawater required the smallest current density compared to specimens polarized in 3.5% NaCl. The reason for this could be due to the thicker calcareous films that were formed on specimens polarized in seawater. 161




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Figure 1 Electrochemical cell Reference electrode (SCE)

Anode (zinc wire)

work electrode (steel rod)

Figure 2 Corrosion potential variation B1

B2

B3

B4

B5

B6

–600 E (mV vs SCE)

–700 –800 –900 –1,000 –1,100 –1,200 0

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 t (days)

Figure 3 Protection potential of the galvanic pair CS-Zn

E (mV vs SCE)

–500 –600 –700

P1

P4

P2

P3

P5

P6

–800 –900 –1,000 –1,100 –1,200 0

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 t (days)

Table I Depolarization potentials Seawater

3.5% NaCl solution

Specimen P1 P2 P3 P4 P5 P6

After 58 days with CP Inst. off. 21,047 21,072 21,072 21,030 21,017 21,033

4h 2 928 2 935 2 936 2 830 2 821 2 852

After 118 days with CP

24 h 2 815 2 860 2 865 2 742 2 743 2 775

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Inst off 2 1,048 2 1,046 2 1,046 2 1,030 2 1,028 2 1,026

4h 2942 2950 2945 2953 2810 2829

24 h 2873 2897 2895 2796 2759 2775

After 205 days with CP Inst. off. 21,051 21,031 21,031 21,034 21,034 21,031

4h 2929 2895 2891 2896 2812 2842

24 h 2873 2841 2839 2776 2752 2775




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Figure 4 Current densities measured during 220 days under CP 100

i galv (mA/m2)

P1

P2

P3

P4

P5

P6

10

1

0.1 0

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 t (days)

on rebar surfaces with CP, dispersed bubbles were observed but did not change to form an adherent and uniform layer.

3.5 Visual changes After five days of CP in seawater, dispersed bubbles were observed on the rebars surfaces (cathodes), and as time passed these surface bubbles changed to form an adherent and uniform white coating on the surface (Figure 5). According to the difference in surface appearance between specimens (B1 and P2) it was evident that the CP connection helped in the formation of the compound layer on the rebar surface. In the NaCl solution,

3.6 SEM and EDS examination Rebar surface immersed in seawater without CP After 49 day of exposure in seawater, Figure 6 shows two zones of the steel rod (B1). Table II presents the chemical composition determined at these zones. The layer in Zone 1

Figure 5 Visual changes on steel surface of B1 and P2 1 day exposure no CP

2 days exposure no CP

5 days exposure under CP

49 days exposure no CP (B1)

41 days exposure under CP (P2)

19 days exposure under CP

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Figure 6 Micrograph of specimen B1 after 49 day of exposure in seawater, showing analyzed zones identified as 1 and 2

Figure 7 Micrograph of specimen P1 after 41 exposure days in seawater under CP, showing analyzed zones, identified as 1 through 4

Encapsuling resin Deposits

Oxide layer steel 16.8 µm

steel

20 µm

80 µm

Table II Chemical composition of specimen B1 after 49 exposure days in seawater Element Fe O Mn

Weight % Zone 1 (oxide layer)

Weight % Zone 2 (steel)

86.50 12.40 1.09

98.81 – 1.19

Table III Chemical composition of specimen P1 after 41 exposure days in seawater under CP Element Zn O Cl Fe Mg S Mn Ca C

(oxide layer) was formed by iron, manganese and oxygen, and at the Zone 2 (rebar) consisted only of iron and manganese. Rebar surface with CP immersed in seawater Specimen P1 (protected) was taken out from the electrolyte (seawater) after 41 days of the CP connection with a zinc anode wire, and its surface was examined using the SEM, see Figure 7. Using EDS the area identified as Zone 1 was the composition of the outer layer of the white product, Zone 2 was the composition of the intermediate oxide layer, Zone 3 was the composition of oxide adhering to the steel rod (inner layer), and Zone 4 corresponded to the steel rod composition. Table III shows the chemical composition of specimen P1 after 41 exposure days in seawater under CP.

Weight % Zone 1

Weight % Zone 2

Weight % Zone 3

Weight % Zone 4

51.64 16.18 13.02 9.52 4.40 3.90 1.08 0.24 –

6.03 23.84 2.22 8.25 1.02 0.39 – 41.39 0.17

– 5.35 3.21 86.74 2.23 – 0.94 1.51 –

– – – 91.41 – – 0.97 – 0.76

found to be the same shiny metal at the end of the experiment as it was at the start. For steel rods immersed in seawater (P1-P3) it was observed over time that the current density decreased to a steady value (Figure 4). This result was attributed to the chemical composition the electrolyte. Seawater consists of many salts and numerous organic and inorganic particles in suspension. Its main characteristics are salinity and chlorinity and, from the corrosion point of view, DO content which ranges from 4 to 8 mg/l, depending on temperature and depth. Seawater is slightly alkaline with a pH about 8.0 but when it is contaminated by acids, such as in coastal regions near power stations burning fossil-fuels generating acidic rains, the pH can diminish to 6 or 5. An important feature of CP in seawater is the formation of calcareous deposits. It is generally agreed that the calcareous deposit that forms comprises a relatively thin, uniform, Mg-rich inner layer, presumed to be magnesium hydroxide, and a thicker outer layer of overlapping aragonite needles (Luo et al., 1991; Zamanzade and Shahrabi, 2007). During the calcareous deposit formation, the active surface progressively decreases,

4. Discussion Current density and deposits on the surface of the steel When cathodically polarizing a metal surface the following processes occur at the metal/electrolyte interface: increase in solution pH, decrease in anodic dissolution kinetics, increase in oxygen reduction kinetics (though this may be limited by mass transport) and increase in hydrogen evolution kinetics (if the potential is sufficiently negative). As a result of the above processes, various changes happen to the metal surface. For all of the polarized specimens, morphological changes to the metal surface occurred during the test period. No specimen was 164




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and then the anode dissolution and the rate of reaction are lowered. Hence, calcareous deposit has the beneficial effect of reducing the current required for an efficient protection. The deposit layer acts as a physical barrier that can cause polarization of the interface as a result of oxygen diffusion limitation, thereby protecting the surface (Solı´s and Genesca´, 2011). Thus, the current densities of all of the specimens studied were found to decrease with time, suggesting that an insulating coating was progressively blocking the steel surface. No calcareous deposits were identified in the blanks. This showed that films on the metal surface are direct result of applying CP. On the other hand, according to the criteria for protection under the NACE RP 0285 and TM 0101, the CP system was effective for the samples immersed in seawater (P1-P3). The current density in NaCl solution (P4-P6) also decreased as time passed, although there was no presence of calcareous deposits because the chemical composition of the electrolyte was different. Leeds showed that on specimens exposed to pure 3.5% NaCl where no calcareous deposits were present, the most coherent films formed on specimens that were polarized between 2 1.3 and 2 1.4 V (Ag/AgCl/3.5% NaCl). These specimens had the lowest corrosion rates and surface films were composed of magnetite (Leeds, 2009). Other studies carried out by Leeds identified iron corrosion products as a major constituent of the surface films. Magnetite was found to form on the metal surface as the potential was made more negative and it also formed a coherent film that was protective in nature (Leeds and Cottis, 2004). According to the criteria for protection under the NACE RP 0285 and TM 0101, the CP system was effective on steel rods immersed in the 3.5% NaCl solution (P4-P6). This meant that the presence of calcareous deposits contributed to reduced current density, but is not primarily responsible for the effectiveness of CP. The current decreased for all specimens between the start current and the end current. At the end of the experiments, the specimens polarized in seawater required the smallest current density compared to specimens polarized in 3.5% NaCl. The reason for this could be due to the thicker calcareous films that form on specimens polarized in seawater. Something, such as the surface film, caused a very significant reduction in current by blocking off the specimen surface, leaving less steel exposed to receive current. Also important is the fact that the films must be relatively non-conducting by insulating away the specimen surface.

calcium and the salts were attributed to the chemical composition of the seawater. Considering the opinion of Leeds (2009), who identified using X-ray diffraction and energy dispersive analysis that as the applied potential was made more negative (with CP), the constituents of the film/deposit changed from consisting of predominantly iron corrosion products to consisting of calcium carbonate containing products, calcite and aragonite (Leeds, 2009), the present research confirms that the application of cathodic current leads to the formation of calcareous deposits on the protected steel surface. In the blanks (without CP), no calcareous deposits were formed on the surface. In NaCl solution, no visible deposit was perceived on the steel surface. However, Leeds (2009) reported that corrosion products formed on the freely corroding specimen immersed in NaCl solution were akaganeite (b-FeOOH), goethite (a-FeOOH), lepidocrocite (g-FeOOH) and magnetite (Fe3O4), and as the applied potential became more negative only the iron corrosion products goethite (a-FeOOH), lepidocrocite (g-FeOOH) and magnetite (Fe3O4) were identified. Further research is necessary on the chemical composition of such deposits to clarify the composition of products formed on steel surfaces under CP.

5. Conclusions .

.

.

.

As the Eprotection and potential depolarization values measured meet the criteria of 100 mV in the seawater and 3.5%, NaCl solution, the steel rods were adequately protected. Reduced galvanic currents measured after a certain time under CP were associated with the formation of deposits on the steel surfaces, suggesting that the film acts as an insulator blocking access to the metal surface. The effectiveness of CP can be attributed mostly to the formation of an iron oxide film. In seawater, the formation of calcareous deposits contributes to reduced current density, but is not primarily responsible for the effectiveness of the CP.

References ASTM A496 (2001), Standard Specification for Steel Wire, Deformed, for Concrete Reinforcement. ASTM C876 (2009), Standard Test Method for Half-Cell Potentials of Uncoated Reinforcing Steel in Concrete. ASTM G3 (2010), Standard Practice for Conventions Applicable to Electrochemical Measurements in Corrosion Testing. ASTM G52 (2011), Standard Practice for Exposing and Evaluating Metals and Alloys in Surface Seawater. Kenichi, A. and Isamu, K. (2003), “Corrosion protection of steel by calcareous electrodeposition in seawater: part 1 – mechanism of electrodeposition”, IHI Engineering Review, Vol. 36 No. 3. Kim, D.-K. and Scantlebury, J.D. (2004), “AC corrosion of mild steel in marine environments and the effects of cathodic protection”, The Journal of Corrosion Science and Engineering, No. 13, p. 9. Leeds, S.S. (2009), “The influence of cathodically generated surface films on corrosion and the currently accepted criteria for cathodic protection”, paper presented at NACE Corrosion Conference & Expo, Paper No. 09548.

SEM and EDS examination Morphological changes of specimens Table III shows for specimens exposed in seawater under CP, the chemical composition of the inner layer, or the composition of oxide adhering to the steel rod (Zone 3), had the highest Fe content, accompanied by oxygen, chloride, magnesium, manganese and calcium concentrations. This indicates that this layer comprised mainly steel corrosion products. The analysis results from layers formed in Zones 1 and 2 showed that the chemical elements were similar. The presence high of zinc in the Zone 1 (composition of the outer layer of the white product) was attributed to oxidation of the anode present in the electrolyte and the salts content was 4 attributed to seawater salts, e.g. Cl-, SO2 2 and Mg. In Zone 2 (composition of the intermediate layer) the presence of 165




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Leeds, S.S. and Cottis, R.A. (2004), “The effect of surface films on cathodic protection”, Journal of Corrosion Science and Engineering, Vol. 9 No. 3. Luo, J.S., Lee, R.U., Chen, T.Y., Hartt, W.H. and Smith, S.W. (1991), “Formation of calcareous deposits under different modes of cathodic polarization”, Corrosion, Vol. 47 No. 3. Miyata, Y. and Wakabayshi, T. (2006), “Estimation of consumption of a sacrificial anode from cathode potential in seawater environment”, The Journal of Corrosion Science and Engineering, Vol. 9 No. 13. NACE Standard RP0285 (2002), Application of Cathodic Protection for External Surfaces of Steel Well Casings. NACE Standard TM0101 (2001), Measurement Techniques Related to Criteria for Cathodic Protection on Underground or Submerged Metallic Tank Systems. NCHRP SYNTHESIS 398 (2009), A Synthesis of Highway Practice Cathodic Protection for Life Extension of Existing Reinforced Concrete Bridge Elements, Transportation Research Board, Washington, DC. Rousseau, C., Baraud, F., Leleyter, L., Jeannin, M. and Gil, O. (2010), “Calcareous deposit formed under cathodic protection in the presence of natural marine sediments: a 12 month experiment”, Corrosion Science, Vol. 52, pp. 2206-2218. Solı´s, J.L. and Genesca´, J. (2011), “Influence of calcareous deposits on galvanic CP in seawater”, Materials Performance, Vol. 50 No. 9. Yang, Y.F., Scantlebury, J.D. and Koroleva, E. (2012), “Underprotection of mild steel in seawater and the role of the calcareous film”, Corrosion, Vol. 68, pp. 432-440. Zamanzade, M. and Shahrabi, T. (2007), “Improvement of corrosion protection properties of calcareous deposits on carbon steel by pulse cathodic protection in artificial sea water”, Anti-Corrosion Methods and Materials, Vol. 54, pp. 74-81.

Dr Jose´ Trinidad Pe´rez Quiroz, Chemical Engineer Metallurgical, graduated from the Universidad Nacional Autońoma de Mexico in 1998 and obtained a Master’s degree in Science (Metallurgy) from the Universidad Nacional Autońoma de Mexico in 2001. He carried out Doctoral studies in Engineering at the Universidad Nacional Autońoma de Mexico 2006-2009 and has worked at the Instituto Mexicano del Transporte since 2000, researching infrastructure made of concrete, coatings and new fuels. He has served as Professor at the Universidad Nacional Autońoma de Mexico, Instituto Tecnolo´gico de Quere´taro and Universidad Marista. Dr Benjamıń Valdez Salas is the Director of the Institute of Engineering of the University of Baja California, member of the Mexican Academy of Sciences and the National System of Researchers of Mexico. He was granted the BS degree in Chemical Engineering, the MSc degree in Chemistry and a PhD in Chemistry by the Autonomous University of Guadalajara. He has been Guest Editor for several special issues in journals on materials and member of the editorial boards of Corrosion Reviews, Corrosion Engineering Science and Technology and Revista Metalurgia. He is the Coordinator of the National Corrosion Network and a Full Professor at the University of Baja California, participating in activities of basic research, technological development and teaching in the postgraduate programs at the UABC and the Autonomous University of Campeche. His activities include research on the topics: corrosion and materials, electrochemical and industrial processes, chemical processing of agricultural and natural products, and consultancy in corrosion control in industrial plants and environments. He is author of books, chapters in books and scientific articles on electrochemistry, biodeterioration and corrosion of materials and general chemistry. He is the head of the Corrosion and Materials Department and the founder of the Master and Doctoral program in Sciences and Engineering for UABC. His professional career includes collaboration with the chemical, oil, water and energy industries of Mexico, and the preservation of the industrial infrastructure.

Further reading

Dr Miguel Martıńez Madrid is a researcher at the Mexican Transport Research Institute. He obtained his BS in Chemistry Engineering from the Autonomous University of Mexico and his ME and PhD in Chemical Engineering from University of Cambridge. He is a member of the National System of Researchers (level 1).

Neville, A. and Morizot, A. (2002), “Calcareous scales formed by cathodic protection – an assessment of characteristics and kinetics”, Journal of Crystal Growth, Vol. 243, pp. 490-502. Wolfson, S.L. and Hartt, W.H. (1981), “An initial investigation of calcareous deposits upon cathodic steel surfaces in sea water”, Corrosion, Vol. 37 No. 2.

Andre´s Torres Acosta is a researcher at the Mexican Transport Research Institute. He obtained his BS in Civil Engineering from the College of Engineering at the Autonomous University of Yucatan, Mexico and his ME and PhD in Civil Engineering from University of South Florida (USF). He also is the Research Coordinator of the Marist University of Queretaro. His research interest is in the field of construction materials and structures, with special emphasis on durability of concrete structures, electrochemical techniques to determine steel corrosion kinetics, corrosion inhibitors, and load capacity of corroded structures. He also is interested in the study and repair of historical buildings, bridges and royal roads.

About the authors Mariela Rendoń Belmonte is studying for a PhD in Chemistry Engineering at the University of Baja California. She obtained a BS in Chemical Engineering from the Technological Institute of Oaxaca, Mexico and ME in Electrochemistry from CIDETEQ (Center for Research and Technological Development in Electrochemistry) Quere´taro, Me´xico. Mariela Rendoń Belmonte is the corresponding author and can be contacted at: marielarb17@ hotmail.com 166




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Jesu´s Porcayo Calderoń has a PhD in Chemical Sciences from the National Autonomous University of Mexico (UNAM). He is a researcher at the Electrical Research Institute (IIE – Mexico), with more than 20 years of experience in corrosion and protection of materials. His main areas of interest are the metallic coatings and high temperature corrosion processes. He has several publications in the field of corrosion and is a member of the National System of Researchers (Conacyt – Mexico).

Dr Miguel Schorr Wiener graduated in Chemistry, has a Master’s degree in Materials Engineering and is Doctor Honoris Causa of the UABC. He is a consultant to “Corrosion Control in Industry” and is a materials and corrosion specialist. He is Editorial Board Member of Corrosion Engineering Science and Technology published by The Institute of Materials, Minerals and Mining. London, UK and is a member of the National System of Researchers (level 2).

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