Zn/55Al coating microstructure and corrosion mechanism

Moreira, Anna Ramus; Panossian, Zehbour; Camargo, Peña; Moreira, Marcelo Ferreira; Silva, I.C. da; Carvalho, José Eduardo Ribeiro de

doi:10.1016/j.corsci.2005.02.012

Cited by 64 publications

(38 citation statements)

References 3 publications

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“…Due to the commercial availability of the analyzed samples, several studies of their microstructure can be found in literature . The different phases in the metal coating are formed as a function of the hot dipping process.…”

Section: Methodsmentioning

confidence: 99%

Corrosion product identification at the cut edge of aluminum-rich metal-coated steel

Alvarez-Pampliega

Bergh

Strycker

et al. 2014

Materials and Corrosion

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The formation of corrosion product at the cut edge of aluminum-rich metalcoated steel is reported in the present work. Painted metal-coated steel samples with different amounts of Al in the metal coating, were immersed in a 0.05 M NaCl solution. The ex situ analysis of the corrosion products formed was carried out by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), Raman and Fourier transform infrared (FT-IR) spectroscopy. The role of these products is discussed along with the influence of Al content in the metal coating. Figure 4. EDX mappings comparison between (a) hot dip Al-Zn steel immersed 2 h in 0.05 M NaCl and (b) 40 h www.matcorr.com

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Section: Methodsmentioning

confidence: 99%

Corrosion product identification at the cut edge of aluminum-rich metal-coated steel

Alvarez-Pampliega

Bergh

Strycker

et al. 2014

Materials and Corrosion

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“…Ramus Moreira et al identified two different phases in the interdendritic areas, one of the phases is aluminum-rich containing zinc while the other is zinc-rich containing aluminum. 41 It was concluded that the atmospheric corrosion process begins in an aluminum rich phase present in the interdendritic areas. As indicated in Figure 3, the Al content measured by SEM-EDS in zinc rich phase ranges between 3% up to 29% at some locations such as close to the surface.…”

Section: Discussionmentioning

confidence: 99%

Atmospheric Corrosion of Zinc-Aluminum Alloyed Coated Steel in Depleted Carbon Dioxide Environments

LeBozec

Thierry

Persson

et al. 2018

J. Electrochem. Soc.

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NaCl induced corrosion of Zn-0.2Al, Zn-5Al and Zn-55Al coated steel was investigated at low and ambient CO 2 levels. Weight loss measurements revealed an enhancement of the corrosion of Zn-0.2Al and particularly Zn-5Al in low CO 2 . This was connected to an increase of surface pH in a low CO 2 atmosphere promoting the formation of ZnO and layered double hydroxide for Zn-5Al. For Zn-55Al, CO 2 depletion did not affect the surface pH due to the acidification effect of Al 3+ . Preferential dissolution of zinc rich phase was observed on cross-sections, particularly in depleted CO 2 experiments. Different sequences of corrosion product formation were proposed for the different Zn-Al coatings. Among Zn-Al coated steels, which are widely used in the construction industry as a better corrosion resistant alternative to replace hot-dip galvanized steel (HDG), two main compositions may be found i.e. Galfan containing 5% aluminum (Zn-5Al) and Galvalume containing 55% aluminum and about 1.6% Si (Zn-55Al). These Zn-Al coatings indeed present a better corrosion performance than HDG in marine and industrial atmospheres, where the main corrosive elements are chloride from seawater aerosols and sulfur dioxide from fume emissions. 1-3 The corrosion rate upon long term field exposure was generally 1.5 to 2 and 2 to 4 times lower than that of HDG for Zn-5Al and Zn-55Al, respectively. Hydrotalcite compounds identified in the corrosion products are believed to play an important role in the corrosion protection. Their formation in the interdendritic areas of Zn-55Al blocks the cathodic reaction because of their inability to act as cathodes, and thus, the overall corrosion rate should decrease.More recently, new zinc coatings alloyed with aluminum and magnesium (i.e. typically 1 to 4 wt% of magnesium and aluminum), showing better corrosion properties than HDG, have been developed for continuous galvanized steel sheet. [4][5][6][7][8][9][10][11][12][13] From the extensive literature on the atmospheric corrosion of zinc in field exposures and laboratory tests, [14][15][16][17][18][19][20][21][22][23] zinc is indeed well known to be highly affected by chloride and sulfur dioxide in particular. The level of CO 2 in the atmosphere has also been reported to have a noticeable influence on the corrosion of zinc 24-27 and zinc coatings including HDG, Zn-5Al and Zn-Al-Mg (ZM). 28 Thus, an enhancement of the corrosion of zinc and zinc coated steel has been observed in depleted CO 2 conditions, which may be achieved in confined situations or under paints for example. Such results were also observed on aluminum and aluminum alloys, 26 as well as on magnesium and magnesium alloys. [29][30][31] Whilst the corrosion performance of Zn-5Al and ZM coated steel is always superior to HDG in chloride containing environments, the situation is opposite in low CO 2 atmosphere, presumably due to the rather high pH of the surface, which induces a more rapid dissolution of zinc and the aluminum phases. 28 In the present study, the aim was to examine the effect of ...

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“…. The outer layer is composed of aluminum‐rich dendrites surrounded by a zinc‐rich interdendritic phase intersected with silicon particles . Typically, this layer has a thickness of 25 µm.…”

Section: Resultsmentioning

confidence: 99%

“…This VPD difference is in agreement with previous works on aluminum intermetallics, particulary those containing iron. The higher Fe content shifts the potential towards more positive values and therefore these particles have a crucial role in the local initiation of pitting corrosion . The following order of nobility between the different phases on hot dip aluminized steel is proposed:

Steel > LIL (F {normale}_{2} A {normall}_{5}) > UIL (FeA {normall}_{3}) > FeA {normall}_{3} needles > Al matrix .

…”

Section: Discussionmentioning

confidence: 98%

Scanning Kelvin force microscopy study at the cut-edge of aluminum rich metal coated steel

Alvarez-Pampliega

González-García

Bergh

et al. 2013

Materials and Corrosion

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This work aims to characterize the electrochemical behaviour of the phases observed on the cross‐sections of different hot dip aluminum‐rich metal coatings on steel. In this framework, scanning Kelvin probe coupled with atomic force microscopy was used to establish the differences of Volta potential on the cross‐sections as function of the chemical composition of the different phases present on each system. Chemical analysis of the cross‐sections was carried out with scanning electron microscope coupled with energy dispersive X‐ray analysis. Then the differences in nobility among the different layers have been reported here and a galvanic series of the different sublayers has been established.

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Zn/55Al coating microstructure and corrosion mechanism

Cited by 64 publications

References 3 publications

Corrosion product identification at the cut edge of aluminum-rich metal-coated steel

Corrosion product identification at the cut edge of aluminum-rich metal-coated steel

Atmospheric Corrosion of Zinc-Aluminum Alloyed Coated Steel in Depleted Carbon Dioxide Environments

Scanning Kelvin force microscopy study at the cut-edge of aluminum rich metal coated steel

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