Determination of Passivation Film Thickness for Hot Dip Galvanising
Author: Robby
Determination methods of hot dip galvanising passivation film thickness mainly include the following:
Weighing method: this method is carried out in accordance with the requirements of GB/T4956, and the thickness of the galvanised layer is calculated by measuring the weight of the galvanised layer. The specific operation is to strip the galvanised layer from the substrate and weigh it, which is converted into the thickness of the galvanised layer according to the density of zinc (7.2 g/cm3). This method is destructive and is suitable for small quantities of steel grating.
Magnetic method: this is a non-destructive test method, carried out in accordance with GB/T4956. This method uses a magnetic thickness gauge to measure on the basic measuring surface of the steel grating. Usually at least 6 measuring points are taken on each basic measuring surface and the average value is taken as the thickness of the galvanised layer in that area. The magnetic method is suitable for on-site quality control within a factory because its measurement area is small and individual measurements may be lower than the overall average thickness.
X-ray fluorescence spectrometry: This method is commonly used to determine the quality of the post-treatment film on galvanised sheets. The quality of the passivation film is calculated by determining the content of specific elements (e.g. element Cr and element Si) by means of X-ray fluorescence spectroscopy. This method is suitable for the inspection of passivation films on galvanised sheets.
Each of these methods has its own advantages and disadvantages, and the selection of the appropriate method depends on the specific testing needs and conditions. For example, weighing is accurate but destructive; magnetic methods are suitable for on-site quality control and are non-destructive; and X-ray fluorescence spectroscopy is suitable for the determination of specific components.