Argyropoulos V. Et Al. Corrosion Inhibitors and Protective Coatings Used for Conservation Metal Objects. 2007 | Corrosion | Alloy

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Argyropoulos V. Et Al. Corrosion Inhibitors and Protective Coatings Used for Conservation Metal Objects. 2007
  1. INTRODUCTION Under the auspices of the European 6 th FrameworkINCO project PROMET, the consortium collected infor-mation from professional conservators-restorers (C-R) onthe types of corrosion inhibitors and protective coatingsused to protect museum objects made of either copper,iron, silver or gold alloys. A questionnaire was designed inEnglish and was then translated into Arabic, French,Greek, Spanish, including also Czech, and posted on thePROMET Internet portal, The ques-tionnaire asked general information about the type of col-lection (i.e., archaeological, historical, or modern), and theconservation methods and practices used for the applica-tion of corrosion inhibitors and/or coatings. The opinionsof the conservators as to the effectiveness of these methodswere also recorded.To date around 54 responses were collected from con-servation professionals from ten (10) countries in theMediterranean Basin: Egypt, France, Greece, Italy, Jor-dan, Malta, Morocco, Spain, Syria, Turkey as well as CzechRepublic. This paper outlines the statistical assessment of the results of the survey and highlights the problems andneeds for further research in this field. The purpose of ourresearch was to understand C-Rs’ practices in Mediter-ranean Basin, and to stimulate discussion for further re-search and training.   2. DEVELOPMENT OF C-R EDUCATION AND PRO-FESSION IN THE MEDITERRANEAN BASIN Apart from the questionnaire, each partner was askedto collect information concerning the level of educationaltraining and professional status of C-Rs in each of the par-ticipating countries of PROMET. The aim was to establishthe basis for the know-how of professional C-Rs working inmuseums.Our survey found that all of the participating countrieshave a law that protects cultural property, in the most partestablished sometime during the 20 th century. Table 1 liststhe level of C-R education and date of establishment. Allcountries, except for Morocco and Syria, offer C-R educa-tion at a University level, but in most cases has only recent-ly been establishedTable 1 clearly shows that the C-R profession is quitenew for most of the participating countries, and many haveonly recently established laws protecting the C-R profes-sion. 3. THE QUESTIONNAIRE The questionnaire was separated in different parts.The first part asks for general information for the institu-tion (e.g., public or private museum), including informa-tion on the type of collection and how many C-Rs work atthe institution. 166 A survey of the types of corrosion inhibitors and protective coatingsused for the conservation of metal objects from museum collectionsin the Mediterranean basin Vasilike Argyropoulos, Maria Giannoulaki, Giorgos P. Michalakakos, Amalia SiatouDepartment of Conservation of Antiquities & Works of Art, Technological Education Institution(TEI) of Athens Ag. Spyridonos, Aigaleo, 12210, GREECETel: 0030-210-5385459Fax: 0030-210-5385406e-mail: bessie@teiath.gr50 museums were surveyed from Egypt, France, Greece, Italy, Jordan, Malta, Morocco, Spain, Syria, Turkey,including Czech Republic to determine the types of corrosion inhibitors and coatings used by conservators-re-storers to protect indoor museum objects made either of copper, iron, silver, or gold alloys. The results foundthat the most popular corrosion inhibitor for copper alloy objects is benzotriazole. For iron alloy objects, notmany conservator-restorers use corrosion inhibitors, except in Europe where tannic acid is the most favoured.Paraloid ® B72 is the most popular protective coating for archaeological or historical copper, iron, silver, andgold alloys. The paper provides an analysis of the survey and identifies the areas for further training or researchin the Mediterranean basin.Keywords: survey, inhibitors, coatings, museum collections AP°YPO¶OY§OYTELOS30-01-0811:03™ÂÏ›‰·166  A survey of the types of corrosion inhibitors and protective coatings used in the Mediterranean basin Then according to the type of metal, i.e. copper, iron,silver or gold alloys, a general description of the types of objects and types of conservation methods used for theseobjects, i.e. cleaning, stabilization etc., is given. Thesetwo parts provide the background information for the in-stitution and C-Rs’ practices.Our statistical analysis was conducted for the re-maining sections, where each institution must list thetypes of corrosion inhibitors and coatings used for eachtype of metal alloy to protect the collection. The respon-dent first provides a category for the response accordingto the following type of collections: A1 and 2 (Archaeo-logical), H1 and 2 (Historical), and M1 and 2 (Modern),and 1 and 2 refers to stable and active corrosion prod-ucts respectively. Such categorization was necessary formuseums that house mixed collections, and to ascertainif coatings for example are being applied to objects withactive or stable corrosion products.Next, how the surface was prepared prior to applica-tion of coating or corrosion inhibitor was also filled in, aswell as the method of application and drying of the ob-ject. The C-Rs were also asked to fill in the expected lifeduration of the products, both given by the manufactur-er as well as what they have experienced in practice. Fur-thermore, they also had to describe the frequency withwhich they applied all the coatings and corrosion in-hibitors that they listed in the previous section, and if there is a combination of corrosion inhibitors and/orcoatings that they use together. Finally, the C-Rs werealso requested to fill in their assessment of the success orfailure of the coating systems that they have used in thepast. 4. THE RESPONDENTS All the participating partners of PROMET submit-ted completed questionnaires from national and region-al institutions involved in the conservation field.To summarize, Czech Republic and Turkey providedresponses from one institute, Egypt, France and Maltafrom two institutes, Syria from three, Jordan, Moroccoand Italy from four institutes, Spain from 8 institutesand finally Greece from nineteen institutes.The partners were asked only to provide one ques-tionnaire per institution – since it was presumed that thesame conservation methods or protocols, and thus cor-rosion inhibitors and/or coatings are being used in a mu-seum. However, for Syria, this is not the case, and de-pending on their training, C-Rs working for the samemuseum may in fact have different conservation proto-cols. Also, revising the list of respondents per country, itcan be observed that some countries provided more re-sponses than others. For example, Greece had the mostresponses, 19, as opposed to Turkey with only one re-sponse. In some cases, the partners involved in the pro-ject had better access to museums and were able to getmore responses than others. In other cases, such as Syr-ia, Jordan, Malta, Morocco etc., there are few or no C-Rprofessionals working in museums. Also, in some coun-tries, like France, most C-R professionals have their ownprivate practices, and treat museum objects in their laband then return them to the museum. Thus, in this casethe C-R professionals may have no knowledge as to theeffectiveness of the corrosion inhibitor and/or coatingapplied. Thus, this questionnaire was not adequately de-signed for them. 5. STATISTICAL ANALYSIS Due to the sample size, and to provide a balance tothe interpretation of the results, statistical analysis wasconducted for three groups, G1: Greece, G2: Europe(Czech Republic, France, Italy, Malta, Spain, andTurkey) and G3: rest of Mediterranean (Egypt, Jordan,Morocco, and Syria). The statistical package SPSS ver-sion 12 was used to create according to the three groups,frequency tables, crosstabs, histograms, and piecharts.The information assessed using this method was only forthe types of corrosion inhibitors and coatings applied ac-cording to each type of metal alloy, copper, iron, silver,and gold. 167 Table 1 Level of C-R Education and Professional Status of C-Rs for participating countries of PROMETCountry C-R Date of Univ. Level 3 or Date of Professional Date of Law C-R Date of Masters/Ph.D. Est. more years Est. C-R body Est. Profession Est.Egypt Y 1975 Y 1988 Y - Y -France Y 2005 Y 1973 Y 1992 Y 2002Greece N - Y 1985 Y 1976 Y 1996Italy Y 1990 Y 1990 Y 1985 Y 2000Jordan Y 2004 Y 2003 N - N -Malta Y 2003 Y 1999 Y 2006 Y 2002Morocco N - N - N - Y 1992Spain Y 1981 Y 1942 N - N -Syria N - N - N - N -Turkey Y 1993 Y 1994 Y 2005 N -Czech R. N - Y 2005 Y 1990 Y 1987 AP°YPO¶OY§OYTELOS30-01-0811:03™ÂÏ›‰·167  V. Argyropoulos et al. 6. BACKGROUND INFORMATION Certain background information was not assessedusing statistics, but is discussed here, since it leads oneto understand the approach taken by C-R professionalsat museums.For Group 1: Greece, the majority of respondentswork in museums, mostly with archaeological collec-tions, but also many have historical or both types of col-lections. The number of C-Rs working on the collectionvaries from 1 part-time to 25 full-time. The majority of collections have all types of metal alloys. Most C-Rs useeither mechanical or chemical cleaning for all types of metals objects. However, C-Rs prefer mechanicalcleaning for iron and gold alloys. Electrolyticcleaning/stabilization is not common, expect in one ortwo cases. Furthermore, most C-Rs in Greece do notconduct dechlorination methods for archaeological ironor copper alloy objects.For Group 2: Europe, the majority of respondentswork in museums, mostly with archaeological collection,but some have historical collections or in one case mod-ern. The number of C-Rs working on the collectionvaries from 1 part-time to 30 full-time. Again the majori-ty of the C-Rs use either mechanical or chemical clean-ing for all types of metal objects. Very few C-Rs in Euro-pean group use electrolytic methods. However, muchmore C-Rs in this group than for the group from Greececonduct dechlorination methods for both copper andiron alloy objects.For Group 3: Mediterranean, the majority of re-spondents work in museums either with archaeologicalor mixed collections, archaeological and historical.These museums have either no C-Rs to 12 full-time plus7 part-time (Egyptian Museum). Again the majority of C-Rs in Mediterranean use either mechanical and/orchemical methods to clean all types of metal objects.Only in two museums the staff applies electrolytic meth-ods, but more importantly no dechlorination methodsare used to stabilize copper and iron alloy objects. 7. THE RESULTS – CORROSION INHIBITORS7.1 Copper Alloys The majority of respondents from all three groupsuse 3% benzotriazole in ethanol solution. However,there are some C-Rs that do not use corrosion inhibitorsfor copper alloy objects. Interestingly, the method inwhich the corrosion inhibitor is applied varies for thegroups as seen in Figure 1. Greek C-Rs prefer to im-merse the object in the inhibitor, where as in the rest of the Mediterranean the inhibitor is applied by brush. InEurope, immersion is preferred or a combination of im-mersion plus brush.Figure 1 Method of application for BTA in ethanol 3% 7.2 Iron Alloys In Greece, the majority of respondents do not use acorrosion inhibitor for iron alloys, whereas few use tannicacid. Interestingly, many C-Rs in the Mediterranean use3-5% benzotriazole in ethanol to stablize iron alloy ob-jects. In Europe, the majority use tannic acid for iron al-loys, along with some other types of commercial products. 7.3 Silver Alloys Very few C-Rs amongst all groups tend to use a corro-sion inhibitor for silver alloy objects, but when they do so,it is usually 3% benzotriazole in ethanol. 8. THE RESULTS – COATINGS Our survey found that for copper, iron, and silver al-loys, C-Rs tend to use the same coatings regardless of thetype of object (historical or archaeological), and type of corrosion products (stable or active) on the surface. Sincemost of the respondents had archaeological collections,the results for these pie charts are presented here. 8.1 Copper Alloys – Greece The majority of C-Rs prefer to use Incralac as a coat-ing for archaeological or historical copper alloy objects asseen in Figure 2. 168 Figure 2 Coatings for copper alloys archaeological objectswith stable corrosion products - Greece 8.2 Copper Alloys- Europe In Europe, the most popular coating for archaeologi-cal or historical copper alloy objects is Paraloid B72 asshown in Figure 3. AP°YPO¶OY§OYTELOS30-01-0811:03™ÂÏ›‰·168
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