样品表面呈现球状特征（图4a和a1），这与BSA分子聚集有关并导致表面高度增加。浸渍 1 天后，表面明显出现晶界（图 4b），导致 Ra 增加。除了较高的 Ra 值 46.3 ± 1.0 nm（图 4c1）外，3 d 样品观察到类似的形态（图 4c）。可以清楚地看到，晶界高于 3D 图像中的晶粒（图 4a1-c1），这意味着在初始浸泡阶段，晶界上有更多的 BSA 吸附。该结果与荧光图像和 SEM 图像一致。 5 d 样品表面出现一些聚集体，这可能是 Ra 值增加 97.8 ± 6.8 nm 的原因（图 4d1）。 7 d 后，大部分谷物被含 BSA 的结构占据（图 4e），导致 Ra 增加。浸泡 14 天后，样品表面显示出相似的形态。晶界随着时间逐渐消失（图 4f-h），Ra 值继续上升（图 4f1-h1）。可以推断，金属基体持续溶解，同时含 BSA 的腐蚀产物在表面不断积累，导致浸渍过程中 Ra 值增加。

The sample surface presents globular features (Fig. 4a and a1), which are related to the BSA molecule aggregations and lead to an increase of surface height. After 1 d immersion grain boundaries apparently show up on the surface (Fig. 4b), resulting in an increase of Ra. The similar morphology is observed for the 3 d sample (Fig. 4c) except for a higher Ra value of 46.3 ± 1.0 nm (Fig. 4c1). It can be clearly seen that the grain boundaries are higher than the grains from the 3D images (Fig. 4a1–c1), implying more BSA adsorption on the grain boundaries in the initial immersion stage. This result is consistent with the fluorescence images and SEM images. Some aggregations appear on the 5 d sample surface, which could account for the increased Ra value of 97.8 ± 6.8 nm (Fig. 4d1). And after 7 d most parts of the grain are occupied by BSA-containing structures (Fig. 4e), resulting in an increase of Ra. The sample surfaces show similar morphologies after immersion for 14 d. The grain boundaries gradually disappear with time (Fig. 4f–h) and the Ra values continue to rise up (Fig. 4f1–h1). It can be deduced that the metal matrix dissolute sustainably and at the same time the BSA-containing corrosion products accumulate constantly on the surfaces, resulting in the increase of Ra value during the immersion.