| Tinplate/chrome plate is a kind of functional materials obtained by plating a layer of tin/chroimum on both surfaces of the cold rolled mild steel. It has not only the mechanical properties of plate, but also the corrosion resistance and beautiful performance of the layer, which are widely used in food packaging fields. However, tinplate/chrome plate must be printed and coated before the application.So it is the important theoretical and practical significance to research the influence of surface oxygen content on tinplate/chrome plate on lacquered adhesion.This paper is based on laboratory research,on-site production oriented, in order to improve tin/chrome plate lacquer adhesion for the purpose, respectively by scanning electron microscope (SEM), energy spectrum analyzer (EDS) and cross experiment inspect.In addition, Cr conternt and its structure are comfirmed by X-ray photoelectron spectrometer (XPS) and thermogravimetric analyzer (E-t curves). The main conclusions are as follows:(1) XPS is used to confirm the layer structure of tinplate/chrome plate:the passivation film of tinplate is made up of Cr, Cr2O3and Cr (OH)3, and their component proportion are8.58%,34.71%and8.58%respectively; chrome plate is composed of Cr2O3, CrOOH, Cr (OH)3and H2O.The percentage of Cr and O element composition are22.77%and69.32%respectively.(2) Tinplate suitable passivation conditions are determined as follows:the passivation liquid concentration of25g·L-1, passivation temperature of45℃〠passivation current density of0.4A-cm"2, passivation solution pH of4.3.(3) Current density has important influence on both one-step and two-step chromium plating process.If current density is lower, the generated less coating and uneven distribution, existence of plating leakage, affecting the quality of the chrome plate;while the current density is too high, the chrome plate turns yellow, even burning.(4) The oxygen content on the surface of the tinplate/chrom plate has important influence on the lacquer adhesion of tinplate/chrome plate:the tinplate has excellent lacquer adhesion under the condition of the certain passivation, when tinplate passivation time is controlled between3～7s. At the same time, chroimum in the passivation film is fixed at31.5～37.8mg·m-2, and the content oxygen of19.7～23.7mg·m-2. For one-step chromium plating process, the chrome plate has the best lacquer adhesion when the electroplating time is controlled at9～17s. For two-step chromium plating process, the chrome plate has the best lacquer adhesion under the condition of metal chromium electroplating process is same, when plating chromic oxide time is3～7s. In addition, chromium on the surface of chrome plate is50.63～75.38mg·m-2, oxygen content of154.14～198.64mg·m-2.(5)The baking progress after paint has important influence on both lacquer adhesion and corrosion resistance of tinplate/chrome plate.For tinplate, when the baking temperature is200℃and the time is15min, tinplate has the excellent lacquer adhesion and corrosion resistance. For chrome plate, when the baking temperature is200℃and the time is20min, chrome plate has the excellent lacquer adhesion and corrosion resistance(6) With improvement of chrome oxide layer thickness, the moisture content on the surface of chrome plate is increasing. When the chrome oxide layer thickness is thicker than8mg·m-2, the moisture content is more than4%.But when the chrome oxide layer thickness is thicker than10mg·m-2, the moisture content is greater than10%.(7) Combined with tinplate/chrome plate surface oxide coating and the corresponding amount of shows, chrome plate finish is superior to the finishing of tinplate, which was mainly due to higher chrome plate chromium and oxygen content. |
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