To achieve the anti-corrosion effect, each single side of the substrate should be coated with at least three isolation film layers, which are chemical conversion coating, bottom coating and surface coating.The colour besmear line in the early days had besmear 2 only, namely have coating of a chemical conversion coating and coating of also bottom also face only coating, but because anticorrosive effect is not good, now colour besmear line is besmear normally 3 or above, some home appliance board is besmear according to actual need even 4 or 5.This is why the following sections introduced the color coating unit will have two coating and two drying, three coating and three drying, four coating and four drying and other technical processes, generally speaking, the color coating line is used for printing color coating board production.
The samples were impregnated in a certain concentration of acid and base solution for a certain period of time.The acid and base resistance test is suitable for the evaluation of acid and base resistance of color coating.
Before the test, the gloss and chromaticity coordinates of the sample were measured.The samples were then immersed in 50mL/L of hydrochloric acid solution or 50g/L of sodium hydroxide solution for a specified time.Finally, the gloss and chroma coordinate values of the sample were taken out and the color difference was calculated. According to GB/T 1766, the samples were evaluated for light loss grade, color change grade, foaming grade and peeling grade, etc. The worst value of the parallel sample was the test result.