Evaluation of surface activity of hot-dip galvanized steel after alkaline cleaning / Ville Saarimaa in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 17, N° 1 (01/2020)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 17, N° 1 (01/2020) . - p. 285-292 Titre : Evaluation of surface activity of hot-dip galvanized steel after alkaline cleaning Type de document : texte imprimé Auteurs : Ville Saarimaa, Auteur ; Carl Lange, Auteur ; Teemu Paunikallio, Auteur ; Aaretti Kaleva, Auteur ; Juha-Pekka Nikkanen, Auteur ; Erkki Levänen, Auteur ; Pasi Väisänen, Auteur ; Antti Markkula, Auteur Année de publication : 2020 Article en page(s) : p. 285-292 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Acier L'acier est un alliage métallique utilisé dans les domaines de la construction métallique et de la construction mécanique. L'acier est constitué d'au moins deux éléments, le fer, très majoritaire, et le carbone, dans des proportions comprises entre 0,02 % et 2 % en masse1. C'est essentiellement la teneur en carbone qui confère à l'alliage les propriétés du métal qu'on appelle "acier". Il existe d’autres métaux à base de fer qui ne sont pas des aciers comme les fontes et les ferronickels par exemple. Alumine Bases (chimie) Caractérisation Chimie des surfaces Chrome -- Suppression ou remplacement Dioxyde de carbone Fluides supercritiques Surfaces -- Nettoyage Zinc Index. décimale : 667.9 Revêtements et enduits Résumé : The surface activity of hot-dip galvanized steel was evaluated after alkaline cleaning by exposing the cleaned specimens in humid supercritical carbon dioxide, followed by extraction and quantification of the formed corrosion products. Different free alkalinities of the cleaning bath were studied to obtain information on the evolution of zinc surface activity at different levels of surface etching. Surface reactivity of uncleaned galvanized steel is restricted and local, with major contributions from grain boundaries and intermetallic particles. Formation of zinc corrosion products took place in uncleaned samples exclusively on and around these sites. Al2O3 removal by alkaline cleaning gradually increased the surface activity. The major increase in surface activity was achieved when increasing the free alkalinity from 0.5 to 4.0 mEq/L, which was shown by formation of zinc corrosion products within zinc grains. The surface activity was confirmed by applying a titanium hexafluoride pretreatment on the cleaned panels and measuring the lateral microscale uniformity of the formed layer. The uniformity increased when larger areas of galvanized steel became activated by alkaline cleaning. Reactivity of zinc is rather difficult to quantify when setting up an industrial cleaning sequence for galvanized steel. Controlled exposure of cleaned samples in humid supercritical carbon dioxide, followed by quantification of oxidized zinc, provides a straightforward method to evaluate zinc reactivity. Note de contenu : - MATERIALS AND METHODS : Materials - Determination of free alkalinity - Humid supercritical carbon dioxide exposure - Quantification of oxidized zinc - Cleaning and pretreatment - Surface characterizations - RESULTS : Effect of free alkalinity on Al2O3 removal - Exposure of cleaned HDG samples to humid scCO2 - Distribution of pretreatment chemical on cleaned samples DOI : 10.1007/s11998-019-00272-9 En ligne : https://link.springer.com/content/pdf/10.1007/s11998-019-00272-9.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=33745 [article]

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Improvement of barrier properties of Cr-free pretreatments for coil-coated products / Ville Saarimaa in JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, Vol. 12, N° 4 (07/2015)  

[article]  inJOURNAL OF COATINGS TECHNOLOGY AND RESEARCH > Vol. 12, N° 4 (07/2015) . - p. 721-730 Titre : Improvement of barrier properties of Cr-free pretreatments for coil-coated products Type de document : texte imprimé Auteurs : Ville Saarimaa, Auteur ; Antti Markkula, Auteur ; Jyrki Juhanoja, Auteur ; Bengt-Johan Skrifvars, Auteur Année de publication : 2015 Article en page(s) : p. 721-730 Note générale : Bibliogr. Langues : Américain (ame) Catégories : Coil coatings Laque et laquage Matériaux -- Propriétés barrières Peinture sur panneau Résistance à l'humidité Index. décimale : 667.9 Revêtements et enduits Résumé : Humidity resistance of pretreated and coil-coated panels was evaluated with a special emphasis on the process parameters that govern the uniformity and barrier properties of hexafluorotitanic acid-based pretreatment layers. Humidity resistance tests showed that good barrier effect was obtained with pretreatments in the coating weight range of about 2–17 mg Ti/m2. It was further verified by rinsing experiments that a fully reacted pretreatment layer is achieved at the very low end of the optimal coating weight range. Increasing the coating weight leads to the formation of precipitated, loosely bonded porous structure, which was detrimental to humidity resistance. In addition to the coating weight, the microscale pretreatment layer uniformity is of utmost importance for good barrier properties. Electron probe microanalysis measurements provide an efficient tool to assess the pretreatment layer uniformity and facilitate monitoring of process adjustments with clear correlation to humidity resistance properties of painted panels. The surface condition of the hot dip-galvanized steel and the material of the application rolls were found to strongly affect the uniformity of the pretreatment layers. Note de contenu : - EXPERIMENTAL : Materials - Sample preparation - Surface characterization - Humidity resistance testing - RESULTS AND DISCUSSION : Influence of pretreatment coating weight on humidity resistance of painted panels - Evaluation of pretreatment layer retention - SEM imaging of pretreated samples - Influence of surface cleaning on pretreatment layer formation - Influence of roll material and pressure on pretreatment layer formation DOI : 10.1007/s11998-015-9663-6 En ligne : https://link.springer.com/content/pdf/10.1007%2Fs11998-015-9663-6.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=24406 [article]

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