Supercritical carbon dioxide treatment of hot dip galvanized steel as a surface treatment before coating

Convenient extraction method for quantification of thin zinc patina layers

“…The 2 bands at 1520 and 1383 cm −1 disappeared after the first glycine extraction, and a single band at ~1390 cm −1 ( v 3 CO 3 2− antisymmetric stretching vibration) appeared (sample 3, Figure ). Furthermore, sharp bands at ~862 cm −1 ( v 2 mode of CO 3 2− ) and ~743 cm −1 ( v 4 in phase bending mode) suggested that the zinc hydroxy carbonate nanowire structure had been dissolved by glycine, and the residual patina consisted of zinc carbonate . Previous studies support the stability of ZnCO 3 at the conditions that were employed in our study …”

“…The scCO 2 treatments were performed in a cylindrical vessel (height 11 cm, width 5.4 cm, volume 256 cm 3 ) as described by Kaleva et al An HDG sample (5 × 10 cm) was placed in the vessel, and the vessel was pressurized to 300 bar with CO 2 (≥99.99%, AGA). A precursor solution consisting of 0.5 m‐% Cu(hfac) 2 (copper (II) hexafluoroacetylacetonate hydrate, Sigma‐Aldrich) in 5 mL of deionized H 2 O/EtOH (40/60 vol‐%) was introduced using a co‐solvent pump . The reaction was carried out for 60 minutes at 50°C.…”

“…Formation of zinc corrosion products is initiated by humidity, oxygen, pollutants and salts (like sulfur dioxide and chloride), and carbon dioxide, although precipitation of CO 2 ‐induced, insoluble corrosion products has been shown to slow down the corrosion process . In the absence of pollutants and salts, the initial zinc dissolution products, zinc oxide and hydroxide, are slowly converted into more stable zinc hydroxy carbonates (also termed zinc patina) that can have beneficial properties for zinc coatings . Recently, a method to rapidly deposit a zinc patina layer on hot dip galvanized steel in supercritical carbon dioxide (scCO 2 ) medium was introduced .…”

“…Recently, a method to rapidly deposit a zinc patina layer on hot dip galvanized steel in supercritical carbon dioxide (scCO 2 ) medium was introduced . The formed patina layer was composed of a dense anhydrous zinc carbonate layer adjacent to the metallic zinc coating, and an outer layer of flower‐like zinc nanowires with a chemical composition resembling synthetic zinc hydroxy carbonates . In addition to their potential in coating applications, the synthetic zinc hydroxy carbonate nanomaterials are also intermediates for ZnO nanowires.…”

Atmospheric Corrosion Behavior of Carbon Steel and Galvanized Steel after Exposure in Eretan and Ciwaringin, West Java Province, Indonesia

“…On the basis of results, within 200 days of exposure, there is 45% of the percentage that reach or exceed RH 85%. In addition, the presence of CO2 gas dissolved into a thin layer of electrolytes on the surface of the metal, which leads to the formation of zinc carbonate and hydrozincite in long-term outdoor exposure with little contaminants in open air [29]. However, in the existence of chloride as a marine pollutant, zincite will subsequently react with chloride to form insoluble simonkolleite [25] as follows In Ciwaringin District, the distance of the site from the coastline is around 2000 meters, which the airborne salinity level decreases.…”