钢材表面多重分形随锈蚀龄期的变化规律

Variation of multifractality of corroded steel surface with corrosion age

摘要:

为研究钢材的表面形貌随锈蚀龄期的变化规律,通过中性盐雾环境下的快速锈蚀试验得到9组不同锈蚀龄期的钢板试件,采用PS50三维非接触式表面形貌扫描仪对试件的上、下表面进行扫描,得到表面形貌和粗糙度S_q.根据多重分形理论对表面进行分析,计算其多重分形谱,得到特征参数Δα和Δf的变化规律,并根据这一规律研究试件表面形貌与锈蚀龄期之间的关系.结果表明,随着锈蚀龄期的增加,试件表面的平均Δα呈现出“增大（424.34%）—减小（26.5%）—增大（29.7%）”的变化趋势,该趋势符合四次幂函数曲线；平均Δf则呈现出符合二次曲线的下降（53.2%）趋势.随着锈蚀龄期的增加,1）试件表面的蚀坑形态由深窄型过渡到浅宽型,并进一步演化出了二级蚀坑； 2）试件表面的高度差异经历了“显著增大—增速减缓—渐趋稳定”的变化规律；3）表面不同高度区域之间的过渡越来越平缓.

Abstract:

To investigate the variation of steel surface with corrosion age, specimens were obtained through rapid corrosion test under neutral salt spray environment and divided into 9 groups according to corrosion age. A PS50 3D profiler was employed to acquire the geometric characteristics and roughness of the test pieces surfaces. Multifractal theory was adopted to calculate the multifractal spectrum of the corroded surfaces, and the characteristic parameters (Δα and Δf) were adopted to study the influences of corrosion age on steel surfaces. Results show that as age grew, the average Δα showed an "increasing (424.34%)—decreasing (26.5%)—increasing (29.7%)" tendency, which was consistent with a fourth power function curve, while the average Δf exhibited a significant decline (53.2%) in a quadratic curve. The increase of corrosion age could result in 1) the style changes of the pits on the surfaces from deep-narrow to wide-shallow and finally a secondary pit, 2) a variation of "significantly increasing—slowing down—stabilizing" the altitude difference of the surface, and 3) a gradually smooth transition between different altitude areas.