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Paper No.
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08024
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CORROSION 2008 CONFERE CE & EXPO
COATINGS STRA TEGY FOR FUEL STORAGE AND ENERGY FACILITIES IN MEXICO
L. M. Martinez de la Escalera* and M. Paredes
Corrosion y Proteccion Ingenieria, S.c.
Rio Nazas 6.
Cuemavaca, Morelos. Mexico. 62290.
A. Rios
Aeropuertos y Servicios Auxiliares
Avenida 602 No. 161.
México, Distrito Federal. Mexico. 62290.
1. A. Padilla López-Méndez
Soluciones Para Mantenimiento, C.A.
Av . 119, Torre Ejecutiva, Ofic. 10-4, Valles de Camoruco
Valencia, Venezuela.
J. Genesca
Facultad de Quimica, Universidad Nacional Autonoma de Mexico
Edificio D, Circuito Exterior,
México, Distrito Federal, CP 04500.
1. A. Ascencio and L. Martinez-Gomez
Instituto de Ciencias Físicas, Universidad Nacional Autonoma de Mexico.
Avenida Universidad s/n, Colonia Chamilpa
Cuernavaca, Morelos. 62210, Mexico.
*Also at Facultad de Ciencias Quimicas e Ingenieria, Universidad Autonoma del Estado de Morelos.
Avenida Universidad 1001, Colonia Chamilpa
Cuemavaca, Morelos. 62210, Mexico.
ABSTRACT
We report results of one-year field experience in monitoring atmospheric corros ion and developing field work ofcorrosion damages to assess the performance of the coatings that are currently Copyright ©2008 by NACE lnte rnati ona l. Requests fo r permi ssio n to publis h thrs manuscrrpt in an y fonn, in pan or in w ho le mus t be in wri ti ng to NACE Internati o nal , Copyright Oivisi on, 1440 South creek Ori ve, Hou stO n. Texas 777084. The materi a l present ed and the views expressed In this paper are solely those of the auth or(s) and are not necessRrlly endorsed by the Assoc ialion . Print ed in the USA.
used for the protection of tanks and structures in an industrial facility and four jet fuel storage stations. For this work, we selected sites located at representative climatic conditions of the Mexican territory. The sites included the industrial port of Altamira and the City of Villahermosa, near the coast of the north and southeast Gulf of Mexico, respectively; the city of Tapachula at the coast of the Pacific Ocean; and the inland cities of Mexicali, an extreme hot, dry and sunny location, and Guadalajara, a humid tempered city. Atmospheric conditions at the Gulf of Mexico were found to be very corrosive due to humidity, salinity and chemicals from industrial activity. An analysis of the coating systems and surface preparation that are currently used, as well as of historic records of the plant equipments revealed opportunities to improve the coating systems performance in the future. Modern coating systems and practices were discussed, benchmarked and a final selection was recommended, according to the atmospheric environments in the regions. Keywords: Coatings, surface preparation, atmospheric corros Ion, Gulf of Mexico, polyamide epoxy, polyurethane acrylic, siloxane epoxy.
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INTRODUCTION It is well known that structural material s presently used in many of the locations have severely reduced serviceable life times, because of climate related variables. Atmospheric corrosion is a well known function of airborne components exhibiting significant variation in urban, arid and marine environments. This is especially true in developing regions in Mexico, along the Caribbean coastline and around the Gulf of MĂŠxico where industry and urban expansion are exposing building material s to prolonged humid, marine environments, as well as to high concentrations of industrial pollutants. 1Â7 The ratio of marine perimeter to land area is singularly large in the geography of Mexico. This singular geographic pattern contributes to the diversity of atmospheric conditions such as temperature, humidity, and salinity found presently in Mexico. The industrial activity is also diverse in the Mexican regions, and contributes to the atmospheric corros ion variability. The characterization of atmospheric corrosion in Mexico has been carried out in the past by a group of authors. 5, 8. Previous work in the field has been reported and sorne regions were characterized by regional atmospheres in Mexico long term studies. The 5 ISO 9223 standard has been used to perform a classification in severallocations in Mexic0 . C4 and CS types of regions have been found, and in sorne marine and heavily polluted zones have led to the suggestion of incorporating a C6 level to the ISO standard to characterize the case of sorne extremely corrosive atmospheres found in Mexic0 5 . The present work was motivated by the needs to deveJop more successful strategies for the protection of structures from atmospheric corrosion. Modern coating systems are in great need in order to apply programs where performance and durability are improved. In this paper we comprise a set of case studies of industrial facilities where there was a need of a new strategy for coatings for corros ion control. Among the cases studied was a new two year old energy industrial facility in the Port of Altamira in the Mexican northern part of the Gulf of Mexico. Severe corros ion of atmospheric origin was found in several components of the plant including the electrical substation and towers, stairs and other metallic components of the combined cycle plant. Jet fuel storage tank farms were al so studied in a variety of locations according the geographical and environmental conditions representing the Mexican
national climates, These include the :b ~
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and unsuccessful previous coatings practices for the corros ion protection of tanks and other accessories of jet fuel storage facilities motivated the presently reported work. The final outcome of these studies
2
was c1assifieation of the atmospheric corros ion types In eoatings designs appropriate type c1imate. I 6
loeatíon, and several
FIELD PROCEDURES
the basic meteorologieal climate (Koeppen 's climate classífieation),7-8 the main climatic zones in Mexico are shown in la, along with the loeatíon the area in whích atmospheric are located. of the of México is known as tropical humid, a mean annual relative and mean preeipitatíon than about 1500 mmJyr.
Figure 1. a) Koeppen 's climate c/assification and b) main different environments found for the considered installalions. mean annual temperature is than whieh is about the same temperature as Gulf waters in region. The shoreline surrounding Gulf México been the loeatíon of significant eeonomic with the building of from industrial sites such as and plants, to and schools, and infrastructures including bridges.
Methodology In order to assess the atmospherie corros ion the environments around Mexieo, 5 plaees were evaluated: Tapaehula, Víllahermosa, Guadalajara, Altamira, and Mexíeali. The considered the where as follows: (a) industrial or non industrial area; (b) and weather such as relative humídity, dew point, and average
Evaluation of critical conditions in the Port of Altamira work we field work developed two dífferent One was applied to the industrial in Altamira, a set steel plates over boh monitors of atmospheríc corrosion evaluatíon was perfonned at an electric power plant. Chloride deposition on plant components was al so perfonned, as well as the recompíLation of atmospheric parameters relevant to corrosion. Altamira, four were located within 1 of the Gulf shorelines, where it anticipated that the atmospheric marine corrosion in this tropical will high due However, it could be antícipated that mainly to large amounts and Gulf vary as a result dífferent chloride wiU to geographical ínfluences even corrosívity with other techniques In
plate test material s were 0.10 m x 0.15 m rectangular coupons of thickness 0.003 m for 1 and 1.5 m aboye the ground on insulated racks angled at 10 14. Samples were. exposed environments and north in locations in the water field 8565. 9 Following exposure corrosíon order to weight according to
3
DIS 8467Y Average mass loss was determined from triplicate coupons exposed for three, six, nine and twelve months.
Evaluation of jet fuel tank farms in four airport locations. A different approach was performed for the evaluation of the atmospheric corrosion conditions in a set of four airport jet fuel farm tanks of airports distributed in representative climates of Mexico, where the evaluation included chlorides, nitrates and pH measurements on the surfaces, the atmospheric meteorological parameters as well as a direct evaluation of the performance of the coatings. We performed chemical surface tests in 4 representative areas of the evaluated jet fuel tank fanns. The chemical tests included presence of nitrates, chlorides and pH of the coated structures. Since the airports are official sites of the Mexican National Meteorological System, we could use the database at each location including average relative humidity, and temperature . After evaluating the different variables as well as the chemical tests on the coated structures we were able to classify the corrosive environments as coastallmarine, urban, and desert (Figure lb). This classification applies for all fuel plants of Mexico 's airports.
ResuJts The electric power plant of Altamira was included in the present study because the reported high cOITosion damage during its earIy years in service, and because the results would provide important leaming of the marine cOITosion in (he northem parts of the Gulf of Mexico. ConsequenUy we focused on this site for the anaJysis of corrosion rates, which could refer to the perspectives of cOITosion in the plant, obtaining values during ayear periodo Four different test sites were selected, where cOITosion rates measured values between 43 and 58 microns per year (TabJe 1), which denote the presence of cOITosion agents but in a relatively controlled region.
TABLE 1
MEASURED VALUES FOR CORROSION RATES IN THE PORT OF ALTAMIRA
CORROSION RATES IN THE PORT OF ALT AMIRA
58
C4
2
44
C3
3
43
C3
4
45
C3
In fact, the monthly analysis of these sites allows recognizing a stabilization process, with a high value for the bare test material, and constant values after the third month, matching form this month up to the annuaJ measured average. This is most likely associated with the presence of the oxide layer over the surface of the carbon steel test material. Even when this behavior ca~ be generalized to similar conditions, we evaluated four more sites in order to clarify the effects of the temperature and humidity over the presence of corrosive agents in the
4
atmosphere of each environment (Table 2). Even when it can be considered not as critical the conditions for the selected sites for the airport fuel farm tan.ks, it can be observed that certainly the Altamira environment shows a value of 14 ยก.tg/cm 2 for chlorides, much higher than the other sites; for nitrates, Tapachula and Mexicali are higher than the Altamira measured data (10, 7 and 5 ppm respectively). These parameters, besides the high temperatures for most of the sites allow deterrnining the wide region of parameters that the studied installations in Mexico involved. Besides the relative humidity is clearly the highest for Altamira and the lowest for Mexicali , then the coating selection has to consider these specific conditions. However it can be established that the chemical tests perforrned in the three fuel plants did not reveal an aggressive concentration of nitrates, chlorides, or neither an acidic or basic pH that could represent risks for the application or performance of the actual coating system.
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Site 3
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20.00 000
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2
4
Time, three months period
Figure 2. Corrosion rate 01 carbon steel coupons as alunction 01 exposure time
5
TABLE 2.
CHEMICAL AND METEOROLOGICAL ANALYSIS
FOR THE DIFFERENT EV ALU ATED SITES
CHEMICAL ANALYSIS AND METEOROLOGICAL PARAMETERSOFATMOSPHERESAVERAGES
AItamira
14
5
Tapachula
4
10
Villa hermosa
2
2
Guadalajara
4
Mexicali
7
6
6, 1 6, 8 6, 7 6, 5
33
82
30
74
33
59
27
51
36
32
Evaluation of coating systems in the field. Under a technical evaluation, we can identify several common probiems with the coating systems, which are reported in a general view to establish the parameters for better and conclusive recornmendations. The evaluated installations show coating systems based on a very thin red alkyd primer and one or two coats of a topcoat based on coumarone indene resin with leafing alluminum as the topcoat. The system thickness ranged from 6.6 to 22.9 mi/s . In many instances, there was no evidence of the presence of the red alkyd primer. There are several problems in the coating system. The most common problems found were generalized corros ion in structure walls, joints between ladders and structures, presence of corrosion in non regular welded joints, corros ion in confined spaces such as valves, stairs, tank access doors, vent valves. There was also corros ion in supports of pipeline s connecting tanks, corros ion as a result of welding splatter, and corros ion in fabrication defects and structure irregularities. Poor adhesion of the coating system is also a recurrent problem. This problern is caused by poor surface preparation before the coating application. Adhesion destructive tests were performed in order to evaluate the existence or nonexistence of surface preparation. No surface preparation (i.e., surface profile or anchor pattem) was observed on none of the structures of the fuel plants evaluated. During the survey, historic information of tbe coating systems was required from the airport fuel plants, but no records were available to determine the existence of a coating specification or if a coating inspector was able to evaluate the existing coating system application . Tbe main problem for the eyaluated coating systems involved chalking and cracking as can be observed in the examples of Figure 3. Chalking is the formation of fine powder on the surface of the paint film due to weathering. Cbalking can cause color fading. Al] paints chalk to sorne degree, it is a normal,
6
way the paint film to wear away and provide a good surface for future acrylic latex Generally, alkyd paints chalk more quickly and to a and heavy will cause paint to lose color and become lighter. makes of the surface powder will adversely affect adhesion repainting a problem the extreme and does not provide a sound surface the paint to bond too This is particularly true with water paints which tend not to penetrate and therefore will bond only to as it can be observed Figure 3a. Quality paints may chalk mildly, but still maintain a surface that will not and retajns moisture and weather for many
Figure 3. Main problems oievaluated coating systems. a) Chalking and leafing coaling lo [he UV light. Alkyd coatings tend lO chalk and lose film thickness while they are exposed to the sun. b-d) Cracking with different One reason occurs is when the of a paint is unable to expand to the same degree as the previous occurs common!y when an undercoat has not time to dry, or indeed a paint is encouraged to dry too quickly, for example increasing temperature in a room or if exterior surfaces jn heat. Cracking wiJl also occur if wallpaper adhesive is allowed to on new paintwork (Figure 3b). Different of can from a 3d), and the vv"'",,,,,,, few evidences (Figure 3c) to the whole 10st clearly associated to the level of problem. Evidences denote that was by abras ion and by poor preparation plants, as it is illustrated 4 and 5. Corrosion on and found in by coating failure assisted by abrasion produced physical damage. Alkyd and coumarone indene associated to the have poor abrasion and consequently this problem can type abrasion resistance is defined as the ability of a material to withstand mechanical action such as rubbing, scraping, or erosion, this to remove material from surface. Such ability to maintain the original appearance and structure. The recognizing that abrasion ís clearly present in in zones with use, such as contact induces to lose the coating material.
4. in stairs and supports environment crea tes corros ion and
in the metal
Finally foundation of any system is the surface preparatíon. It is the most important factor in developing a successful coating system. purpose of surface preparation is to remove contaminants that can with adhesion and to develop a surface roughness to promote mechanical of four bond. Destructive tests as well as nondestructive tests were performed at the jet fuel tanks or aboveground a surface preparatíon was tound. Mexican airports. In none of profile or available documented informatíon that could prove that applied system a preparatíon. Also, there was no available specification of the applied 5 determined that a preparation was recommended. shown in the was poorly prepared, the coating was bemg applied, inducing an early degradatíon of coatíng system and substrate.
7
5. no
the applied coating wasfound.
did no! have adequate surface preparation, to lhe not show
CONCLUSIONS
The work been use fui for the of a new tank fanns and other industrial facilities based on field of atmospheric as well as coating performance, application procedures a set of locations territory. analysis involved multiple common problems that were summarized, identifying possible sources problems. conc1usions are associated with requirement of a deeper of the sites, environment, which even though they are not considered critical corrosíve, show particular conditions and adequate coating must them. We found an important potential protection of structures exposed to the by a based mostly on coumarone indene coating application procedures involving almost no
Recommended solutions. Several coatings were proposed for discussing the best altematives for corrosion control of the structures in the analyzed Cost, durability and availabílity were among the critería used for Alternative inc1uded: surface tolerant, and epoxy primer. polyamide, epoxy and epoxy polyamide HB were selected as second or intennediate coats. Acrylic aliphatic and alternate finish coats. organic zinc epoxy primer, a polyamide coat foJlowed by an acrylic aliphatic polyurethane finish coat wíth a thickness of 2 to 3 mils was seen as an economic as well as durable opríon both marine and urban types of environment. In this case the surface preparatíon altemative was or water blast to near white metal the dry, sunny and very hot regíon of Mexicalí a two layer system as a primer, followed by a 5 to 7 mUs of siloxirane epoxy was preparation similar ro the considered in previous mentioned case.
orgalllc epoxy ''''''''''''''''' with a
ACKNOWLEDGMENTS Mexico City, Guadalajara, Tapachula, We are grateful to y Servicios Auxiliares Port of Altamira for the help in perfonning the fieId work. We Villahennosa and Mexicali and to Maura Vianey and Osvaldo also thank the support of as Sandoval in project management. in sample preparatíon and laboratory
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the península of
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9