A novel method for assessing haze in the visual appearance of bright-annealed AISI 430 ferritic stainless steel

Abstract

In this paper, a novel method for evaluating the degree of haze on the surface of bright-finish AISI 430 ferritic stainless steels is presented. Haze is an undesirable effect that typically manifests as a loss of brightness and specularity on the steel surface. Visual inspections are used for quality control, with the tested product compared to reference surfaces. This method is strongly influenced by the visual acuity of the operator and the lighting conditions of the production line. In addition, the use of portable glossmeters does not provide a good correlation between the degree of cloudiness and the parameters of the instrument, which are typically defined for evaluating painted surfaces. Furthermore, neither method allows for a quantification of the degree of haze in the stainless steel, only an acceptance or rejection evaluation. The method described in this paper attempts to overcome these limitations by analyzing gray-level histograms of images of high-contrast Ronchi-type patterns reflected on the steel surfaces. The results show that this method is sensitive to haze and allows the degree of haze on the surfaces of these industrial products to be quantified.

Keywords

• Stainless steel
• Visual appearance
• Image analysis
• Light reflectance value
• Haze