苦味酸是利用直接腐蚀法检测奥氏体晶粒度最常用的金相浸蚀剂之一，为了抑制晶内组织的腐蚀速率，通常会在配方中添加缓蚀剂。选用十二烷基苯磺酸纳作为缓蚀剂，通过调整缓蚀剂的配比，试验了不完全淬火+高温回火组织、完全淬火+高温回火组织以及粒状贝氏体组织奥氏体晶粒度的检测方法。结果表明：增加缓蚀剂的含量，可以有效抑制晶内组织的腐蚀速率。对于完全淬火后高温回火的试样，利用带状偏析，纵向检测奥氏体晶粒度，可以快速腐蚀显示出偏析带的奥氏体晶粒度。试验证实含有高浓度缓蚀剂的苦味酸溶液是一种通用的奥氏体晶粒度腐蚀剂。

Picric acid is one of the most common metallographic etching agent in direct corrosion test of austenite grain size. In order to inhibit the corrosion rate of the intra crystalline structure, corrosion inhibitors are usually added to the formula. Sodium dodecyl benzene sulfonate was selected as corrosion inhibitor. By adjusting the ratio of corrosion inhibitor, the test methods of austenite grain size including partial quenched and high temperature tempered structure, completely quenched and high temperature tempered structure and granular bainite structure were carried out. The results show that increasing the content of corrosion inhibitor can effectively inhibit the corrosion rate of the intra crystalline structure. Longitudinal test of austenite grain size in the banded segregated zone can rapidly corroded austenite grain size of the completely quenched and high temperature tempered samples. Picric acid solution containing high concentration corrosion inhibitor was proved to be a general corrosion agent of austenite grain size.