George Wypych, in Functional Fillers, 2018


The anti-corrosion properties of epoxy composite coatings were improved by addition of functionalized fullerene C60 and graphene.21 Fullerene C60 has the shape of an icosahedron.21 It is built out of carbon atoms located at the nodes of 20 hexagons and 12 pentagons arranged in a cage lattice (diameter 0.7 nm) defined by alternating single and double bonds.21 The nanofillers strongly self-associate into ropes and other structures that are extremely difficult to disperse in polymers, especially graphene which forms irreversible agglomerates due to π–π stacking and van der Waals interactions.21 The functional groups have been grafted on the surface of fullerene and graphene using 3-aminopropyltriethox-ysilane.21 Figure 6.4 shows that the tortuosity of pathway prevents diffusion of corrosive substances.21 The significance of surface grafted groups is not restricted to the improvements in dispersion but also reduces porosity of coating and improves adhesion to steel.21 The anti-corrosion properties of graphene/EP coatings are superior to FC60/EP coatings because of the higher surface area of graphene which makes the diffusion path of permeating corrosive solutions more tortuous.21 Also, excellent electrical conductivity of graphene causes that the electrons are not able to reach a cathodic site.21 There is a limit of filler concentration which is at 0.5 wt%, above which anti-corrosive performance is not improved – most likely because of the aggregation of nanofillers which causes formation of nanocracks assisting diffusion of corrosive substances.21

Figure 6.4. Performance of epoxy composite coatings with appropriate content of fullerene (a) and graphene (b) during corrosion process.

[Adapted, by permission, from Liu, D; Zhao, W; Liu, S; Cen, Q; Xue, Q, Surf. Coat. Technol., 286, 354-64, 2016.]Copyright © 2016

Figure 6.5. Multiwalled carbon nanotubes decorated with titanium dioxide nanoparticles.

[Adapted, by permission, from Kumar, A; Kumar, K; Ghosh, PK; Yadav, KL, Ultrasonics Sonochemistry, 41, 37-46, 2018.]Copyright © 2018

Graphite, graphene, hybrid filler containing carbon nanotubes were used to improve the electrical conductivity and anti-corrosion properties of polyurethane coatings.22 At the same filler loading, the electrical conductivity of hybrid filler system was significantly higher than that of the single filler system (0.77 S/m at 5 wt% while single filler system was not conductive).22 Hybrid filler system had the best electrical conductivity and acceptable anti-corrosion capacity.22

Multiwalled carbon nanotubes were decorated with TiO2 nanoparticles to form a new hybrid structure of filler which was then used in the epoxy composite.23 The blend of both fillers was sonicated in acetone followed by magnetic stirring and drying in vacuum oven.23 The hybrid filler/epoxy nanocomposite exhibited superior anti-corrosion and mechanical performance as compared with the nanocomposite produced by loading of only MWCNTs, TiO2 nanoparticles, or neat epoxy.23 The composite coating reduced corrosion rate on mild steel to 0.87×10−3 from 16.81 mili-inches per year.23

Titanium and its alloys are wildly and successfully used in producing implants for their good mechanical properties, bioactivity, and corrosion resistance.24 To achieve good bioactivity and anti-corrosion properties, the surface of titanium often needs modifications, such as an alkali treatment, anodic oxidation of TiO2 and coatings.24 Graphene oxide and cross-linked gelatin were used in hydroxyapatite coatings preventing corrosion of titanium.24 The coating acted as a barrier that prevented the electrolyte from reaching the metal surface.24 These coatings had better bond strength and corrosion resistance than hydroxyapatite coatings.24

Graphene can accelerate metal corrosion because of its thermodynamic stability and high conductivity.25 A few-layer fluorographene was prepared by a liquid-phase exfoliation method.25 Fluorographene was incorporated into poly(vinyl butyral) coatings to enhance its corrosion protection performances.25 The coating had enhanced barrier property preventing the penetration of aggressive species.25 Unlike graphene, fluorographene cannot promote metal corrosion. Because of its insulating nature, it impedes the formation of metal-filler galvanic corrosion cells.25

The effects of carbon nanofillers morphology (namely carbon black, multiwall carbon nanotubes, and graphene) on the anticorrosive and physicomechanical properties of hyperbranched alkyd resin-based coatings were studied.26 Graphene filler gave the best corrosion resistance.26

3D tomography by automated in situ block face ultramicrotome imaging using an field emission gun-environmental scanning electron microscope was used to study complex corrosion protective paint coatings.27 The method permits 3D observation of paint microstructure, crack formation in coating, morphology and distribution of paint additives, and corrosion inhibitor depletion.27 For the photo-aged and damaged paint sample, a crack was evident that passed through the primer approximately parallel to the substrate surface (Figure 6.6a).27 There was a sharp microcracking (less than 1 μm wide) at the crack-tip within the epoxy matrix.27 The crack was guided along the silica/epoxy interface. Some silica particles were cracked the entire way through.27 The image in Figure 6.6b shows movement of some of the material around the crack, which was evident from the curved particles which should be straight if no movement occurred.27

Figure 6.6. (a) Crack formation in primer, (b) a 3D reconstruction of a section of the specimen.

[Adapted, by permission, from Trueman, A; Knight, S; Colwell, J; Hashimoto, T; Carr, J; Skeldon, P; Thompson, G, Corrosion Sci., 75, 376-85, 2013.]Copyright © 2013

To entrap a corrosion inhibitor agent into a host matrix and avoid its possible weakening/plasticizing toward an organic coating and enable its progressive release under stimuli, the layered double hydroxide framework was selected.28 The layered double hydroxide reservoirs loaded with ethylenediaminetetraacetic acid as well as with chromate, carbonate and chloride anions were dispersed into the epoxy primer coating.28 A deleterious effect of ethylenediaminetetraacetic acid anions was observed when it was free in solution while a prevention of corrosion phenomenon was observed when the same anion was intercalated into layered double hydroxide nanoreservoir (Figure 6.7).28 Such behavior could be attributed to the buffering effect occurring for a large range of pH values thus preventing the copper replating.28 The possible corrosion mechanisms involves diadochy, buffering, and possible complexing reaction against electrolyte salt concentration versus exposure time.28

Figure 6.7. Mechanisms of corrosion prevention of aluminum alloy by incorporation of ethylenediaminetetraacetic acid and layered double hydroxide.

[Adapted, by permission, from Stimpfling, T; Leroux, F; Hintze-Bruening, H, Appl. Clay Sci., 83-84, 32-41, 2013.]Copyright © 2013

An anticorrosive pigment is incorporated in the topcoat of an anticorrosion coating system which greatly reduces the corrosion rate of the substrate metal in the environments of aggressive ions.29 The inorganic cation exchange pigment is selected from the group consisting of a metal ion-exchanged silica, metal ion exchanged alumina, synthesized zeolites, natural zeolites, and natural cation exchangers.29

The coating composition for protecting iron and steel structures contains particulate zinc, conductive pigments, and hollow glass microspheres.30 A conductive pigment is selected from the group consisting of graphite, carbon black, aluminium pigments, black iron oxide, antimony-doped tin oxide, mica coated with antimony-doped tin oxide, carbon nanotubes, and carbon fibers.30 Zinc acts as a sacrificial anodic material and protects the steel substrate, which becomes the cathode.30 Addition of microspheres and conductive pigments reduces microcracking.30

A coating comprising functionalized graphene and polymer protects roll steel, galvanized roll steel, equipment, automobiles, ships, construction and marine structures from corrosion, fouling and UV deterioration.31 The functionalized graphene has 1-10 sheets.31 The functionalized graphene contains a chemical group selected from amino, cyano, carboxylic acid, hydroxyl, isocyanate, aldehyde, epoxide, urea, or anhydride.31 The suitable resin is a phenolic resin, a polyester resin, a polyurethane, or an epoxy resin.31

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Sustainable Cutting Fluids: Thermal, Rheological, Biodegradation, Anti-Corrosion, Storage Stability Studies and its Machining Performance

Kishor K. Gajrani, Mamilla R. Sankar, in Encyclopedia of Renewable and Sustainable Materials, 2020

Concluding Remarks

The physical, thermal, rheological, biodegradation, anti-corrosion and storage stability properties of sustainable BCF and petroleum-based MO are assessed and compared. Machining experiments were conducted with BCF and MO using MQCF technique. The salient findings are as follows:

The flash point of BCF is higher as compared to MO that allows its use for high temperature hard machining.

BCF exhibits less variation from Newtonian behaviour even at higher temperature. Also, its sensitivity to temperature is lower as compared to MO.

As per Standard methods 2005, ultimate biodegradability of BCF and MO is found to be 96.67% and 18.32%, respectively.

BCF showed corrosion breakpoint of 8; whereas MO exhibits corrosion breakpoint of 9 as per ASTM D 4627 standard.

As per ASTM D 3707 standard, BCF shows more remaining emulsion as compared to MO after storage stability test.

Sustainable BCF showed better machining performance as compared to MO in terms of cutting force, feed force, tool-chip interface coefficient of friction and surface roughness due to its high viscosity and better lubricating properties.

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Mechanical properties of bioceramics

M V SWAIN, L-H HE, in Bioceramics and their Clinical Applications, 2008

Publisher Summary

This chapter presents that, because of the excellent biocompatibility, matching shade, good anti-corrosion ability, bioceramics are ever more widely being used in the biomedical field. Most of these bioceramic appliances need to bear forces during their lives. Therefore, the mechanical properties became the most important factors to rank and select proper material. With the rapid development of modern material science and technology, more and more high-strength, high-toughness bioceramics have been developed and introduced into biomedical usage. The ever-more critical evaluation of existing and new bioceramic appliances will greatly increase the security and confidence of the medical usage of these materials. From a mechanical point of view, a bioceramic and its appliances need to meet these standards: similar elastic modulus, hardness, and stress–strain relationship as the natural tissue; high fracture toughness and subcritical crack growth index; good wear resistance and minimal fatigue crack growth susceptibility; and all bioceramic appliances should undergo proper designed proof test to guarantee their quality.

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Corrosion inhibitors for metallic artefacts: temporary protection

E. ROCCA, F. MIRAMBET, in Corrosion of Metallic Heritage Artefacts, 2007

18.1 Introduction

The environment is the main cause of the decay of metallic elements from the cultural heritage. Art curators with the support of analytical science attempt to intervene to stop the deterioration. In many cases, the conservation efforts cannot stop the deterioration process or reverse the ensuing damage, but they can help slow the rate of degradation to ensure a longer existence for artefacts.

The interactions between the metal and its environment are responsible for the electrochemical reactions leading to corrosion. To avoid further degradation and in general the appearance of corrosion products, a more or less insulating barrier must be created on the metallic surface between the object and the atmosphere. Different barrier coatings have been developed, such as anodic oxides, ceramic and inorganic coatings as corrosion inhibitors, organic coatings and conversion coatings. Most of them were first developed for industrial applications. They generally require the removal of the corrosion products, and their application leads to important changes in the visual appearance of the metallic surface. These treatments have also been applied for the outdoor protection of large structures that are part of the cultural heritage, like bridges or buildings protected by French legislation. But for a large proportion of works belonging to the cultural heritage, such as patinated artefacts or sculptures and archaeological artefacts, these protection systems cannot be applied.

For the application of these protective systems in the restoration domain, the selection of an anti-corrosion treatment should be based on the evaluation of different specific criteria:

Storage conditions of the artefact (outdoor, indoor, controlled or uncontrolled environmental conditions)

Presence or absence of corrosion products on the surface which can decrease the efficiency of the treatment

Final visual appearance of the treated object surface which should not be altered

Reversibility of the protective system. Indeed, the removal of the protective system should be easy, to allow future treatments on the object.

Three other criteria are nowadays important to evaluate the replacement of the protection:

The temporary character of some treatments which have to be applied two or three times per year to be efficient

The toxicity of the chemical substance responsible for the inhibition properties

The price of the protection system.

In the first part of this chapter, we present a brief review of the protection systems, except painting systems, currently used for conservation purposes. In the second part, recent researches on a new corrosion inhibitor family will be developed.

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Sustainable development

Vlastimil Kuklík, Jan Kudláček, in Hot-Dip Galvanizing of Steel Structures, 2016

Mining and utilization of zinc can be approached in a similar way. The system of anti-corrosion protection of steel with zinc coating cannot be eliminated from our lives given its huge economic significance, but hot-dip galvanizing could be perceived as an activity that may be acceptable if the main conditions are strictly met:

Renewable resources should be not consumed faster than the rate at which they manage to recover naturally.

Exhaustible resources should not be consumed faster than the rate at which their replacement will be provided and to which a smooth transition will be possible.

The volumes of produced pollutants must not exceed the capacity of the receiving environment.

A part of current profits should be invested to pollution reduction, reduction of waste, increasing efficiency (of products, energy, production processes …) and to looking for new sources of raw materials and energy.

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Tests of hot-dip galvanized coatings and assessment of their quality

Vlastimil Kuklík, Jan Kudláček, in Hot-Dip Galvanizing of Steel Structures, 2016

7.5 Coating adhesion tests

Adhesion of galvanized coating to the substrate does not usually need to be tested. Unlike organic coating materials, where the performance and durability of anti-corrosion protection is directly proportional to the adhesion of the protective layer to the substrate and its consistency, the anti-corrosion effect of a zinc coating is mainly related to cathodic protection. It only becomes efficient when both the electrically conductive metals are in contact, regardless of possible cracks and pores in the coating (see Section 8.1). A properly applied galvanized coating on steel that is suitable for hot-dip galvanizing usually exhibits sufficient adhesion to the substrate. However, what should be kept in mind is that parts with a thick coating require especially careful handling. Mechanical processing of hot-dip galvanized products is considered as non-standard handling of the product from the point of view of coating adhesion.

If the surface treatment purchaser requests adhesion tests, such a test and the required parameters may be agreed with the galvanizer on placing of the order. Adhesion can be measured with the use of a pull-off test in accordance with EN ISO 4624 or EN ISO 16276-1 by means of a special fixture measuring the force required to pull off the coating on a delimited area (Figure 7.6). A suitable adhesive is used to bond a test dolly of corrosion-resistant steel onto a flat surface of a galvanized part. After hardening the adhesive a circular target is marked around the contact surface of the dolly using a fixture and the dolly is pulled off using a special device (pull-off adhesion tester) (Figure 7.7) while the tension required to pull off the dolly is measured. The boundary between the coating layers (or in the adhesive) where the dolly was pulled off is also assessed.

Figure 7.6. Pull-off adhesion tester (two bonded dollies in the foreground).

Figure 7.7. Probe acting upon the dolly.

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Process considerations for nanostructured coatings

Kal Renganathan Sharma, in Anti-Abrasive Nanocoatings, 2015

6.9 Anti-corrosion coating

Graphene has been used to make the thinnest coating known the world over and can be used for protecting metals against corrosion (Sharma, 2014). The potential use of graphene as anti-corrosion coating was discussed in the journal ACS Nano by D. Prasai and his colleagues. Rusting and other corrosion of metals is an important global problem. Contact of metal with air, water, or other substances can cause corrosion. Graphene is a single layer of carbon atoms. It is evaluated for use as anti-corrosion coating. An ounce of graphene arranged in a single layer and comprised of rows of benzene rings can fill the size of 28 football fields. Graphene, whether made directly on copper or nickel or transferred onto another metal, can be used to prevent corrosion. Copper coated with graphene by chemical vapor deposition (CVD) was found to corrode seven times faster than uncoated copper. Nickel coated with multiple layers of graphene was found to corrode at a rate of 20 times slower than uncoated Nickel. The same amount of corrosion protection can be obtained using a single layer of graphene that was obtained using five layers of organic coatings. Graphene coatings may be ideal for applications in industrial microelectronics. They can be used in aircraft, implants and as interconnects.

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Smart composite coatings for corrosion protection of aluminium alloys in aerospace applications

Darya Snihirova, ... M. Fatima Montemor, in Smart Composite Coatings and Membranes, 2016

4.4 Smart anti-corrosion coatings

The most effective corrosion protection strategy requires various functionalities that among others may include corrosion identification with signaling effect, corrosion retardation with water/ion traps, and corrosion inhibition. Zhang and Frankel (1999) added the pH indicator phenolphthalein to an acrylic-based coating and could sense the corrosion onset detecting color change associated with the pH increase caused by the cathodic reaction in the corrosion process. Maia et al. (2013) encapsulated phenolphthalein in silica capsules and added it to water-based epoxy coating applied on AA2024 and magnesium alloy AZ31. In both cases, corrosion-sensing functionalities were developed and the local corrosion onset could be detected by eye due to the color change of phenolphthalein under alkaline pH. Water (Zheludkevich et al., 2005b) and chloride traps (Dias et al., 2013; Tedim et al., 2012) postpone corrosion onset because they delay the ingress of corrosive species to the metallic substrate.

Since corrosion is inevitable, the addition of anti-corrosion pigments, mainly Cr(VI)-containing compounds, has been one of the most effective corrosion-protection strategies in coated Al alloys (Bastos et al., 2005; Seth et al., 2007; Williams et al., 2012; Twite and Bierwagen, 1998; Bohm et al., 2001; Deyá et al., 2007). In spite of progressive restrictions on the use of corrosion inhibitors based on chromates, there are still several Cr(VI)-based compounds/processes used as pigments in anti-corrosion protective systems for aerospace applications. For example, chromic acid is used for anodizing, dichromium tris(chromate) is used as anti-corrosion in surface treatments, and strontium chromate, potassium hydroxyoctaoxodi-zincatedichromate, and pentazinc chromate octahydroxide are used as pigments in anti-corrosion coatings. All of these are carcinogenic and are being researched by REACH regulations. Therefore, the latest developments have been focused on the design of more advanced coatings for corrosion protection, free of Cr(VI)-based pigments. To succeed with this strategy, corrosion-protective coatings combining good barrier properties with functionalities providing effective corrosion protection have been one of the priorities in the aerospace sector. Among these, smart anti-corrosion coatings have been considered to have high potential.

The smart functionality of an anti-corrosion coating for AA2024 can be based on the addition of extra functional additives (corrosion inhibitors) (Feng et al., 2007). Various smart solutions including the ability of self-healing have been reviewed recently (Fedrizzi et al., 2011; Ferreira et al., 2011; Montemor, 2014; Yasakau et al., 2014). The proposed solutions cover various bare materials (Hager et al., 2010; Fischer, 2010), different functionalities for self-repair of polymeric matrices (Feng et al., 2007; Kumar et al., 2006; Murphy and Wudl, 2010), additives for corrosion protection, and coatings with enhanced barrier properties (Hughes et al., 2010; Montemor, 2014), encapsulation of liquid healing agents (Samadzadeh et al., 2010; Murphy and Wudl, 2010), and advanced polymers and composites (Williams et al., 2008; Wu et al., 2008; Bergman and Wudl, 2008; Murphy and Wudl, 2010; Syrett et al., 2010; Burattini et al., 2010; Mauldin and Kessler, 2010; Blaiszik et al., 2010; Shchukin and Möhwald, 2007a).

The strategies that show potential for self-healing corrosion protection, and that have been studied in detail, can be classified according to the respective mechanisms of action. A strategy that has attracted interest among scientists is the encapsulation of functional agents, with healing ability, in micro or nanostructured hosting systems that are then dispersed in the protective-coating matrices. Attempts have been made at the development of systems with multiple protection mechanisms, in which different functionalities for repair of the polymer, water trap, and corrosion inhibition are combined in the same coating.

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List of selected zinc coating technologies

Vlastimil Kuklík, Jan Kudláček, in Hot-Dip Galvanizing of Steel Structures, 2016

1.2 Thermal spraying of zinc (metallizing)

Thermal spraying (Figure 1.2) is used to apply zinc that is melted by flame or electric arc and carried by a gas stream to the sand-blasted surface of the part to be coated. The coating adheres by mechanical adhesion [15]. Pure zinc may be used for thermal spraying for anti-corrosion, but for higher corrosion resistance, alloys of zinc with aluminum are also frequently used. The coating is applied as a layer with the thickness of 80 to 250 μm.

Figure 1.2. A metallizing gun for thermal spraying in the powder version is suitable for repairs of galvanized coating applied by immersion in molten zinc.

For reliable adhesion of a zinc coating applied by metallizing the surface requires pre-treatment by sand-blasting with the use of sharp-edged particles.

After the application of sprayed zinc it is necessary to apply an organic painting material on the deposited coating that will adhere very well in its profile. Combination of zinc coating with organic paint (referred to as a duplex system, see Section 8.3) offers a very good corrosion resistance with regard to efficient synergy of both the materials.

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Service life of hot-dip galvanized coatings

Vlastimil Kuklík, Jan Kudláček, in Hot-Dip Galvanizing of Steel Structures, 2016

8.2 Atmospheric corrosion

In the course of time, the coating thickness is reduced at a variable rate depending on the corrosivity of the environment. Its useful life is indirectly proportional to the corrosion rate, expressed usually as the amount of corrosion loss in micrometers or grams per unit area. The anti-corrosion protection system of a hot-dip galvanized coating is very efficient if the galvanized part is exposed in a clean atmospheric environment. This means an environment where free access of air to the part’s surface is ensured and its possible wetting is temporary and short. The concentration of acidic pollutants in the atmosphere must also be low.

The passivation layer of zinc carbonate is slowly reduced by the action of environmental effects, but it is continuously renewed by zinc contained in the coating. The time for which a zinc coating is able to protect steel from corrosion is derived from the service life of this coating, i.e., the time until it is consumed by corrosion. This time period is directly proportional to the thickness of the applied zinc coating and indirectly proportional to the corrosion rate of zinc in the particular corrosion environment [48]. The values of average annual corrosion losses depending on the corrosivity of the environment are published in a number of technical standards (e.g., EN ISO 12944-2 or ISO 9223). Both of them classify atmospheres in six classes C1 to CX by increasing corrosivity (see Table 8.1).

Table 8.1. Corrosion rates of zinc in accordance with EN ISO 9223:2012

Corrosivity class Corrosion rate (rcorr)
Zinc Units
C1 very low well-ventilated interiors of commercial, office, and residential premises with a maintained temperature and without the risk of moisture condensation, dry or cool outdoor areas with very low air pollution (deserts, central Antarctica) rcorr≤0.7 [g.m−2.year−1]
rcorr≤0.1 [µm.year−1]
C2 low ventilated sports halls, production halls, garages, storage premises without a maintained temperature with clean environment and the possibility of short-term moisture condensation, dry or cold climatic zone with a short wetting period, clean country environment 0.7<rcorr≤5 [g.m−2.year−1]
0.1<rcorr≤0,7 [µm.year−1]
C3 medium environment of industrial halls with medium pollution (food processing plants, laundries, dairies, breweries, mild climate regions with medium and tropic regions with low air pollution, municipal environment, maritime environment with low salinity) 5<rcorr≤15 [g.m−2.year −1]
0.7<rcorr≤2,1 [µm.year−1]
C4 high environment with high frequency of condensation and high pollution, indoor swimming pools, mild climate regions with high and tropic regions with medium air pollution, industrial areas with medium air pollution and maritime atmospheres with medium salinity, aerosol of road salt 15<rcorr≤30 [g.m−2.year−1]
2.1<rcorr≤4.2 [µm.year−1]
C5 very high poorly ventilated environment with very high frequency of condensation or high pollution from production processes and mines, mild climate regions with very high and tropic regions with high air pollution, industrial areas with high air pollution and maritime atmospheres with high salinity 30<rcorr≤60 [g.m−2.year−1]
4.2<rcorr≤8.4 [µm.year−1]
CX extreme premises with permanent condensation and high pollution from production processes, regions with very high air pollution, tropical maritime regions with frequent and long wetting and very high salinity, environment of fishing ship with direct exposure to salt water 60<rcorr≤180 [g.m−2.year−1]
8.4<rcorr≤25 [µm.year−1]

A sufficiently thick patina layer is created on a zinc coating in the course of a few weeks after its application. Until then the coating has reduced ability to resist corrosive influences of the environment and being moist. During this time it can be covered by corrosion products – white rust. In normal climatic conditions, effects on the zinc coating by white rust show a temporary character. Climatic influences gradually cause removal of corrosion products from the surface and their gradual replacement by a layer of patina (zinc carbonate). After several months’ exposure, the surface that has been affected by white rust acquires the same patina appearance as the remaining coating parts that have not been attacked by corrosion. As with any other product, galvanized coatings are subject to certain restrictive conditions limiting the suitability of their application and way of use. On condition the user respects the guarantee conditions and eliminates possible harmful local influences; galvanized coatings are able to provide steel products with reliable anti-corrosion protection for a very long time. In most applications they represent the most suitable, efficient, and reliable anti-corrosion system.

In many European countries, initiatives from national galvanizers’ associations have given to rise to maps of the atmospheric corrosion rate of zinc. These tools are used for quick reference. The zinc corrosion rates in the UK and Republic of Ireland shown in Figure 8.7 [49] were separated into five categories (these categories are not intended to be correlated to the “C categories” of ISO 9223). In Table 8.2, according to color-coding of each map block, the value of the average annual corrosion losses of zinc due to atmospheric corrosion, i.e., without considering micro-climatic influences, is deduced. The design of a particular anti-corrosion system must also take local influences into account. They should include any major air pollution source in the vicinity, industrial activity, or an unsuitable structural design of the part allowing deposition of solid pollutants in inadequately designed structural elements, etc. (see also Section 9.11).

Figure 8.7. The Zinc Millennium Map.

Image is provided courtesy of Galvanizers Association.

Table 8.2. Atmospheric zinc corrosion rates in the UK are represented by five categories

Corrosion category 1 2 3 4 5
Average corrosion rate [μm/year] 0.5 1 1.5 2 2.5
Average life of 85 μm galvanized coating [years] 170 85 57 43 34

With knowledge of the corrosion rate of zinc in a particular environment, it is relatively easy to estimate the service life of a galvanized coating. With knowledge of the minimum coating thickness (Tables 7.2 or 7.3Table 7.2Table 7.3) and the corrosion rate of zinc in the particular environment, the expected service life is easy to determine. EN ISO 1461 sets minimum coating thickness values; however, it does not prevent the purchaser agreeing different values with the galvanizing plant. The application of a coating with a required thickness can be influenced by selecting the thickness of the semi-product or by using silicon-killed steel. A thicker coating may also be achieved by blasting the part’s surface with a fine sharp-edged abrasive material (see Section 5.4.3).

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