SIST EN ISO 14713-2:2010
(Main)Zinc coatings - Guidelines and recommendations for the protection against corrosion of iron and steel in structures - Part 2: Hot dip galvanizing (ISO 14713-2:2009)
Zinc coatings - Guidelines and recommendations for the protection against corrosion of iron and steel in structures - Part 2: Hot dip galvanizing (ISO 14713-2:2009)
This part of ISO 14713 provides guidelines and recommendations regarding the general principles of design which are appropriate for articles to be hot dip galvanized for corrosion protection. The protection afforded by the hot dip galvanized coating to the article will depend upon the method of
application of the coating, the design of the article and the specific environment to which the article is exposed. The hot dip galvanized article can be further protected by application of additional coatings (outside the scope of this part of ISO 14713), such as organic coatings (paints or powder coatings). When applied to hot dip galvanized articles, this combination of coatings is often known as a “duplex system”. The guidelines and recommendations in this part of ISO 14713 do not deal with the maintenance of corrosion protection in service for steel with hot dip galvanized coatings. Guidance on this subject can be found in ISO 12944-5. Specific product-related requirements (e.g. for hot dip galvanized coatings on tubes or fasteners, etc.) will take precedence over these general recommendations.
Zinküberzüge - Leitfäden und Empfehlungen zum Schutz von Eisen- und Stahlkonstruktionen vor Korrosion - Teil 2: Schmelztauchverzinken (ISO 14713-2:2009)
Dieser Teil von ISO 14713 bietet Leitfäden und Empfehlungen für die allgemeinen Grundlagen der Gestaltung
von Gegenständen, die zum Schutz gegen Korrosion einen Überzug durch Feuerverzinken erhalten.
Der Schutz des Feuerverzinkungsüberzugs für den Gegenstand hängt von dem zum Aufbringen des Überzugs
angewendeten Verfahren, der Gestaltung des Gegenstands und der spezifischen Umgebung des
Gegenstands ab. Der feuerverzinkte Gegenstand kann durch das nachfolgende Aufbringen zusätzlicher
Beschichtungen (die nicht in den Anwendungsbereich dieses Teils von ISO 14713 fallen) geschützt werden,
z. B. organische Beschichtungen (Anstriche oder Pulverbeschichtungen). Bei Anwendung auf feuerverzinkten
Bauteilen wird dieses kombinierte Beschichtungssystem häufig als „Duplex-System“ bezeichnet.
Die Leitfäden und Empfehlungen in diesem Teil von ISO 14713 erfassen nicht die Instandsetzung des
Korrosionsschutzes für Stahl mit Feuerverzinkungsüberzügen unter Einsatzbedingungen. Ein entsprechender
Leitfaden zur Instandsetzung kann in ISO 12944-5 nachgelesen werden.
Anforderungen, die für ein bestimmtes Produkt gelten (z. B. für feuerverzinkte Überzüge auf Rohren oder
Befestigungselementen usw.), haben eine höhere Priorität als die hier angegebenen allgemeinen
Empfehlungen.
Revêtements de zinc - Lignes directrices et recommandations pour la protection contre la corrosion du fer et de l'acier dans les constructions - Partie 2: Galvanisation à chaud (ISO 14713-2:2009)
L'ISO 14713-2:2009 donne des lignes directrices et des recommandations concernant les principes généraux de conception appropriés aux pièces à galvaniser à chaud pour la protection contre la corrosion.
La protection assurée par le revêtement galvanisé à chaud appliqué sur la pièce dépend de la méthode d'application du revêtement, de la conception de la pièce et de l'environnement spécifique auquel la pièce est exposée. La pièce galvanisée à chaud peut également être protégée par l'application de revêtements supplémentaires (non couverts par le domaine d'application de l'ISO 14713-2:2009) tels que des revêtements organiques (peintures et revêtements poudre). Lorsqu'elle est appliquée aux pièces galvanisées à chaud, cette combinaison de revêtements est souvent appelée «système duplex».
Les lignes directrices et recommandations données dans l'ISO 14713-2:2009 ne traitent pas de l'entretien de la protection contre la corrosion en service assurée pour l'acier par des revêtements galvanisés à chaud. Des lignes directrices correspondantes sont fournies dans l'ISO 12944‑5.
Des exigences spécifiques relatives aux produits (par exemple pour les revêtements galvanisés à chaud sur les tubes et les éléments de fixation, etc.) prévalent sur les présentes recommandations générales.
Cinkove prevleke - Smernice in priporočila za zaščito železnih in jeklenih konstrukcij proti koroziji - 2. del: Vroče pocinkavanje (ISO 14713-2:2009)
Ta del ISO 14713 določa smernice in priporočila glede splošnih načel pri projektiranju, ki so primerna za izdelke, ki bodo vroče pocinkani za zaščito proti koroziji. Zaščita, ki jo daje vroča pocinkana prevleka na izdelku, je odvisna od metode nanosa prevleke, načrtovanja izdelka in določenega okolja, kateremu je bil izdelek izpostavljen. Vroče pocinkan izdelek je lahko nadaljnje zaščiten z nanosom dodatnih prevlek (zunaj področja uporabe tega dela ISO 14713), kot so organske prevleke (barve ali prašno barvanje). Ta kombinacija prevlek, uporabljena za vroče pocinkane izdelke, je pogosto poznana kot »dupleks sistem«. Smernice in priporočila v tem delu ISO 14713 se ne nanašajo na vzdrževanje protikorozijske zaščite in popravljanje jekla s cinkovimi prevlekami. Vodilo na to temo se nahaja v ISO 12944-5. Posebne zahteve, ki se nanašajo na izdelke (t.j. za vroče pocinkane prevleke na ceveh ali sponkah itd.), imajo prednost pred temi splošnimi priporočili.
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Zinküberzüge - Leitfäden und Empfehlungen zum Schutz von Eisen- und Stahlkonstruktionen vor Korrosion - Teil 2: Schmelztauchverzinken (ISO 14713-2:2009)Revêtements de zinc - Lignes directrices et recommandations pour la protection contre la corrosion du fer et de l'acier dans les constructions - Partie 2: Galvanisation à chaud (ISO 14713-2:2009)Zinc coatings - Guidelines and recommendations for the protection against corrosion of iron and steel in structures - Part 2: Hot dip galvanizing (ISO 14713-2:2009)91.080.10Kovinske konstrukcijeMetal structures25.220.40Kovinske prevlekeMetallic coatingsICS:Ta slovenski standard je istoveten z:EN ISO 14713-2:2009SIST EN ISO 14713-2:2010en01-marec-2010SIST EN ISO 14713-2:2010SLOVENSKI
STANDARDSIST EN ISO 14713:19991DGRPHãþD
SIST EN ISO 14713-2:2010
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN ISO 14713-2
December 2009 ICS 25.220.40; 91.080.10 Supersedes EN ISO 14713:1999English Version
Zinc coatings - Guidelines and recommendations for the protection against corrosion of iron and steel in structures - Part 2: Hot dip galvanizing (ISO 14713-2:2009)
Revêtements de zinc - Lignes directrices et recommandations pour la protection contre la corrosion du fer et de l'acier dans les constructions - Partie 2: Galvanisation à chaud (ISO 14713-2:2009)
Zinküberzüge - Leitfäden und Empfehlungen zum Schutz von Eisen- und Stahlkonstruktionen vor Korrosion - Teil 2: Schmelztauchverzinken (ISO 14713-2:2009) This European Standard was approved by CEN on 18 November 2009.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2009 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 14713-2:2009: ESIST EN ISO 14713-2:2010
EN ISO 14713-2:2009 (E) 2 Contents Page Foreword .3 SIST EN ISO 14713-2:2010
EN ISO 14713-2:2009 (E) 3 Foreword This document (EN ISO 14713-2:2009) has been prepared by Technical Committee ISO/TC 107 "Metallic and other inorganic coatings" in collaboration with Technical Committee CEN/TC 262 “Metallic and other inorganic coatings”, the secretariat of which is held by BSI. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2010, and conflicting national standards shall be withdrawn at the latest by June 2010. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 14713:1999. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 14713-2:2009 has been approved by CEN as a EN ISO 14713-2:2009 without any modification.
SIST EN ISO 14713-2:2010
SIST EN ISO 14713-2:2010
Reference numberISO 14713-2:2009(E)© ISO 2009
INTERNATIONAL STANDARD ISO14713-2First edition2009-12-15Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron and steel in structures — Part 2: Hot dip galvanizing Revêtements de zinc — Lignes directrices et recommandations pour la protection contre la corrosion du fer et de l'acier dans les constructions — Partie 2: Galvanisation à chaud
SIST EN ISO 14713-2:2010
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SIST EN ISO 14713-2:2010
ISO 14713-2:2009(E) © ISO 2009 – All rights reserved iii Contents Page Foreword.iv 1 Scope.1 2 Normative references.1 3 Terms and definitions.2 4 Design for hot dip galvanizing.2 4.1 General.2 4.2 Surface preparation.2 4.3 Procedures related to design considerations.3 4.4 Design features.3 4.5 Tolerances.3 5 Design for storage and transport.4 6 Effect of article condition on quality of hot dip galvanizing.4 6.1 General.4 6.2 Surface condition.6 6.3 Influence of steel surface roughness on the hot dip galvanized coating thickness.6 6.4 Influence of thermal cutting processes.6 6.5 Effect of internal stresses in the basis steel.6 6.6 Large objects or thick steels.7 6.7 Hot dip galvanizing practice.7 7 Effect of hot dip galvanizing process on the article.8 7.1 Dimensional tolerances on mating thread.8 7.2 Effect of process heat.8 8 After-treatments.8 Annex A (informative)
Preferred designs of articles for hot dip galvanizing.9 Bibliography.18
SIST EN ISO 14713-2:2010
ISO 14713-2:2009(E) iv © ISO 2009 – All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 14713-2 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings, Subcommittee SC 4, Hot dip coatings (galvanized, etc.). This first edition, together with ISO 14713-1 and ISO 14713-3, cancels and replaces ISO 14713:1999, which has been technically revised ISO 14713 consists of the following parts, under the general title Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron and steel in structures: ⎯ Part 1: General principles of design and corrosion resistance ⎯ Part 2: Hot dip galvanizing ⎯ Part 3: Sherardizing The principal changes to this part of ISO 14713 compared to ISO 14713:1999 are the following. ⎯ This part of ISO 14713 only provides design guidance for hot dip galvanizing of articles. ⎯ The normative references (Clause 2) have been updated to take into account the very latest standards available to readers. ⎯ Additional guidance on the effect of the iron/steel surface composition has been provided (6.1.1, Table 1). ⎯ Additional information has been provided on the effect of thermal cutting processes (6.4) and the influence of internal stresses in the basis steel during hot dip galvanizing (6.5).
SIST EN ISO 14713-2:2010
INTERNATIONAL STANDARD ISO 14713-2:2009(E) © ISO 2009 – All rights reserved 1 Zinc coatings — Guidelines and recommendations for the protection against corrosion of iron and steel in structures — Part 2: Hot dip galvanizing 1 Scope This part of ISO 14713 provides guidelines and recommendations regarding the general principles of design which are appropriate for articles to be hot dip galvanized for corrosion protection. The protection afforded by the hot dip galvanized coating to the article will depend upon the method of application of the coating, the design of the article and the specific environment to which the article is exposed. The hot dip galvanized article can be further protected by application of additional coatings (outside the scope of this part of ISO 14713), such as organic coatings (paints or powder coatings). When applied to hot dip galvanized articles, this combination of coatings is often known as a “duplex system”. The guidelines and recommendations in this part of ISO 14713 do not deal with the maintenance of corrosion protection in service for steel with hot dip galvanized coatings. Guidance on this subject can be found in ISO 12944-5. Specific product-related requirements (e.g. for hot dip galvanized coatings on tubes or fasteners, etc.) will take precedence over these general recommendations. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 1461, Hot dip galvanized coatings on fabricated iron and steel articles — Specifications and test methods ISO 4964, Steel — Hardness conversions ISO 8044, Corrosion of metals and alloys — Basic terms and definitions ISO 10684, Fasteners — Hot dip galvanized coatings ISO 12944-5, Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 5: Protective paint systems EN 10210-1, Hot finished structural hollow sections of non-alloy and fine grain steels — Part 1: Technical delivery requirements EN 10219-1, Cold formed welded structural hollow sections of non-alloy and fine grain steels — Part 1: Technical delivery requirements SIST EN ISO 14713-2:2010
ISO 14713-2:2009(E) 2 © ISO 2009 – All rights reserved EN 10240, Internal and/or external protective coatings for steel tubes — Specification for hot dip galvanized coatings applied in automatic plants EN 10346, Continuously hot-dip coated steel flat products — Technical delivery conditions 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 8044 and the following apply. 3.1 hot dip galvanizing formation of a coating of zinc and/or zinc/iron alloys on iron and steel products by dipping prepared steel or cast irons in the zinc melt 3.2 hot dip galvanized coating coating obtained by hot dip galvanizing NOTE The term “hot dip galvanized coating” is subsequently referred to as the “coating”. 4 Design for hot dip galvanizing 4.1 General It is essential that the design of any article required to be finished should take into account not only the function of the article and its method of manufacture but also the limitations imposed by the finish. Annex A illustrates some of the important design features, some of which are specific to hot dip galvanizing. Some internal stresses in the articles to be galvanized will be relieved during the hot dip galvanizing process and this may cause deformation or damage of the coated article. These internal stresses arise from the finishing operations at the fabrication stage, such as cold forming, welding, oxy-cutting or drilling, and from the residual stresses inherited from the rolling mill. The purchaser should seek the advice of the hot dip galvanizer before designing or making a product that is subsequently to be hot dip galvanized, as it may be necessary to adapt the construction of the article for the hot dip galvanizing process. The purchaser should be aware of the two distinct types of hot dip galvanizing and take these distinctions into account when designing articles: a) hot dip galvanizing after fabrication – where, after suitable pretreatment, fabricated iron or steel articles are dipped in a bath containing a zinc melt (see ISO 1461); b) continuous galvanizing – where, after suitable pretreatment, sheet materials are continuously fed through a zinc melt and the hot dip galvanized sheet materials are then used to fabricate an article (see EN 10346). 4.2 Surface preparation The design and the materials used should permit good surface preparation. This is essential for the production of a high-quality coating (see 6.2). Surfaces should be free from defects to ensure a coating of good appearance and serviceability. Graphite exposed at the surface of iron castings interferes with wetting by molten metal and those castings that have been annealed may have silica particles in the surface layers which have to be removed in order to obtain a good-quality hot dipped coating. Grit blasting is recommended both before and after annealing. SIST EN ISO 14713-2:2010
ISO 14713-2:2009(E) © ISO 2009 – All rights reserved 3 4.3 Procedures related to design considerations The hot dip bath and associated plant should be of adequate capacity to process the articles to be hot dip coated with zinc. Preferably, articles should be designed to enable coating in a single dipping operation. Articles that are too large for the available baths may be partially immersed and then reversed for length or depth, so that a complete coating is obtained. Partial immersion (and then dipping for a second time to complete the coating) is less common than the single, complete immersion operation. All work has to be secured during immersion in the baths. Bolt holes are often available. Lifting lugs are often incorporated to assist general handling. Articles may be held in racks or jigs; some contact marks may be visible after hot dip galvanizing in such cases. The dipping operation involves vertical movement out of the bath, but the parts being withdrawn may be inclined at an angle. The processing sequence requires circulation of air, pretreatment liquids and zinc to all surfaces of the work piece. Air pockets prevent local surface preparation and give uncoated surfaces; liquids in enclosed air vaporize at the hot dip galvanizing temperature of about 450 °C and the force generated can cause buckling or explosions; excess zinc may adhere poorly, may look unattractive and is wasteful. Suitable articles, e.g. heat exchangers and gas cylinders, may be hot dip galvanized on the outside only. This involves special techniques and equipment (e.g. to push the article into the bath against the buoyancy of the molten zinc) and a specialist galvanizer should be consulted in advance. 4.4 Design features Preferred design features for articles to be hot dip galvanized are shown in Annex A. WARNING — It is essential that sealed compartments be avoided or be vented, otherwise there is a serious risk of explosion that may cause serious injury to operators. This aspect of design should
be given careful consideration and is essential in order to maintain satisfactory standards of health and safety for operators. The provision of holes for venting and draining tubular fabrications also allows a coating to be formed on the inside surfaces and therefore ensures better protection for the article. Occasionally, at sufficiently high levels of residual stress in the component, stress relief may occur at the hot dip galvanizing temperature. This is one of the main causes of unexpected distortion or cracking of the steel component. Symmetrical sections are preferred and, as far as possible, large variations in thickness or cross-section, e.g. thin sheet welded to thick angles, should be avoided, welding and fabrication techniques should be chosen to minimize the introduction of unbalanced stresses and differential thermal expansion should be minimized during welding and processing. Heat treatment may be desirable before hot dip galvanizing. The purchaser should discuss with the galvanizer the requirements for coating and assembly of fabricated components. Compact sub-assemblies (which occupy minimum bath space) are most economical to galvanize. Welding is preferable before hot dip galvanizing, to ensure a continuous hot dip galvanized coating over the weld. Articles should be designed so as to assist the access and drainage of molten metal and so that air locks are avoided. A smooth profile, avoiding unnecessary edges and corners, assists hot dip galvanizing; this, and bolting after galvanizing, improves long-term corrosion resistance. Holes which are necessary in structures for the hot dip galvanizing process are preferably made before assembly and by cutting or grinding off corners of sections; this facilitates the absence of “pockets” in which excess molten zinc can solidify. When already assembled, burning may be the optimum method of producing holes, as the space available for drilling may not allow the hole to be close enough to the edge or corners. 4.5 Tolerances The thickness of the hot dip coating is determined mainly by the nature and thickness of the steel. On mating surfaces and at holes, extra tolerance should be provided to allow for the thickness of the coating metal. For hot dip galvanized coatings on flat surfaces, an allowance of at least 1 mm has been found satisfactory. See ISO 1461 for definitions of significant surfaces and acceptance criteria for the coating. SIST EN ISO 14713-2:2010
ISO 14713-2:2009(E) 4 © ISO 2009 – All rights reserved For threaded work, the situation is more complicated. For example, for hot dip galvanized and centrifuged nuts and bolts, current practices differ according to the country. Either a) the bolts are threaded according to the tolerances laid down in the appropriate specification without allowance being made for hot dip galvanizing and the nuts are then tapped after coating or b) the bolts are undersized (see e.g. Swedish Standard SS 3194) so that standard threads on hot dip galvanized nuts can be used in all cases. ISO 10684 also provides some guidance. 5 Design for storage and transport Hot dip galvanized work should be stacked securely so that the work can be handled, stored and transported safely. Where there is a specific need to minimize the development of wet-storage staining (primarily basic zinc oxide and zinc hydroxide, formed on the surface of the galvanized coating during storage of work in humid conditions), this should be communicated by the purchaser to the galvanizer at the time of ordering and any relevant control measures should be agreed upon. Such measures might include, for example: storage of work such that free movement of air across the surfaces of the work is allowed, the use of spacers to minimize contact areas on the work, or avoidance of close nesting of work (where the design allows this). In accordance with ISO 1461, the development of wet-storage staining shall not be a cause for rejection, provided the coating thickness remains above the specified minimum requirements. 6 Effect of article condition on quality of hot dip galvanizing 6.1 General Most steels, including unalloyed carbon steels (see e.g. EN 10025-2), fine-grained steels (see e.g. EN 10025-3 and EN 10025-4), quenched and tempered steels, hollow sections that are hot finished (see e.g. EN 10210-1), hollow sections that are cold finished (see e.g. EN 10219-1), reinforcement steels (see e.g. EN 10080), fastener grade steels (see e.g. ISO 898), grey cast iron (see e.g. EN 1561) and malleable cast iron (see e.g. EN 1562), can be hot dip galvanized according to ISO 1461. Where other ferrous metals are to be galvanized, adequate information or samples should be provided by the purchaser for the galvanizer to decide whether these steels can be satisfactorily galvanized. Sulfur-containing free-cutting steels are normally unsuitable. 6.1.1 Material composition Certain elements, in particular silicon (Si) and phosphorus (P), in the steel surface can affect hot dip galvanizing by prolonging the reaction between iron and molten zinc. Therefore, certain steel compositions can achieve more consistent coatings with regard to appearance, thickness and smoothness. The prior history of the steel (e.g. whether hot rolled or cold rolled) can also affect its reaction with molten zinc. Where aesthetics are important or where particular coating thickness or surface smoothness criteria exist, specialist advice on steel selection should be sought prior to fabrication of the article or hot dip galvanizing. Table 1 gives simplified guidance on steel compositions that are associated with certain typical coating characteristics when galvanizing is carried out at temperatures of 445 °C to 460 °C. SIST EN ISO 14713-2:2010
ISO 14713-2:2009(E) © ISO 2009 – All rights reserved 5 Table 1 — Coating characteristics related to steel composition Category Typical levels of reactive elements Additional information Typical coating characteristicsA u 0,04 % Si and < 0,02 % P See Note 1 B 0,14 % Si to 0,25 % Si Fe/Zn alloy may extend through to the coating surface. Coating thickness increases with increasing silicon content. Other elements may also affect steel reactivity. In particular, phosphorus levels greater than 0,035 % will give increased reactivity. Coating has a shiny appearance with a finer texture. Coating structure includes outer zinc layer. C > 0,04 % Si to u 0,14 % Si Excessively thick coatings may be formed. D > 0,25 % Si Coating thickness increases with increasing silicon content. Coating has a darker appearance with a coarser texture. Iron/zinc alloys dominate coating structure and often extend to the coating surface, with reduced resistance to handling damage. NOTE 1 Steels with compositions satisfying the formula Si + 2,5P u 0,09 % are also expected to exhibit these characteristics. For cold rolled steels, these characteristics are expected to be observed when the steel composition satisfies the formula Si + 2,5P u 0,04 %. NOTE 2 The presence of alloying elements (e.g. nickel) in the zinc melt can have a significant effect on the coating characteristics indicated in this table. This table does not provide relevant guidance for high-temperature galvanizing (i.e., immersion in molten zinc at 530 °C to 560 °C). NOTE 3 The steel compositions indicated in this tablewill vary under the influence of other factors and the boundaries of each range will vary accordingly.
6.1.2 Castings Castings should be as free as possible from surface porosity and shrinkage holes and should be cleaned by grit blasting, electrolytic pickling or by other methods especially suitable for castings. Conventional hydrochloric acid pickling does not remove mould-sand deposits, graphite or temper carbon from the surface of cast iron. Grit blasting is necessary to remove these contaminants. Surface cleaning of complex shapes can be undertaken by specialist galvanizing companies using hydrofluoric acid. Care needs to be exercised in the design of cast-iron sections. Small castings of simple shape and solid cross-section do not present problems for galvanizing, provided that the material and surface condition are suitable. Larger castings should have a balanced design with uniform section thicknesses to avoid distortion and cracking due to thermal stress. Large fillet radii and pattern numbers should be used and sharp corners and deep recesses avoided. The rough surface finish which castings tend to possess may result in thicker galvanized coatings than on rolled components. NOTE Castings can take several forms: ⎯ grey iron castings: grey iron has a carbon content of greater than 2 %, the majority of which is graphite in flake form; ⎯ spheroidal graphite (SG) castings: similar to grey iron in many aspects of composition but with carbon present primarily as graphite in spheroidal form, initiated by additions of magnesium or cerium; ⎯ malleable iron castings: black-heart, white-heart and pearlitic. The toughness and workability are derived from annealing processes and no primary graphite is permissible. SIST EN ISO 14713-2:2010
ISO 14713-2:2009(E) 6 © ISO 2009 – All rights reserved 6.2 Surface condition The surface of the basis metal should be clean before dipping into the molten zinc. Degreasing and pickling in acid are the recommended methods of cleaning the surface. Excessive pickling should be avoided. Surface contamination that cannot be removed by pickling, e.g. carbon films (such as rolling oil residues), oil, grease, paint, welding slag, labels, glues, marking materials, fabrication oils and similar impurities, should be removed prior to pickling; this allows for more effective and efficient use of pretreatment materials. The purchaser is responsible for removing such contamination, unless alternative arrangements have been agreed between the galvanizer and the purchaser. 6.3 Influence of steel surface roughness on the hot d
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