蓝点试验
国际标准《不锈钢电解抛光及打磨抛光和酸洗钝化所形成的表面钝化膜检验》ISO15730
酸洗钝化处理质量，根据需要可以采用蓝点试验法来检验。用1克铁K[Fe(CN6)]加3毫升（65%~85%）硝酸HNO3和100毫升水配制成溶液（储存期为一周）。然后用滤纸浸泽溶液后，贴附于待测表面或直接将溶液涂、滴于待测表面，30秒内观察显现蓝点情况，有蓝点为不合格。需要注意的是该实验需待酸洗钝化表面基本干燥后进行。试验后也应该将试验液体冲洗干净。
蓝点试验的基本原理为：若表面钝化膜不完善或有铁离子污染，就会有游离的铁离子存在，那么即可发生如下反应：
Fe2 + K[Fe(CN6)] = K[Fe(CN6)]↓深蓝 + 2K
Blue point test
International standard ‘Inspection of the Passivation Film Which is Formed on the Surface o
f the Stainless Steel after Electrolytic Polishing, Burnishing and Pickling/Passivation’ ISO15730
We can use the blue point test to check the quality of pickling/passivation treatment. First, use 1g potassium ferricyanide K3[Fe(CN6)], 3mL (65%~85%) nitric acid and 100mLwater to compound the solution(storage time: one week). Soak the filter paper in the solution, then paste the filter paper on the pending test surface or directly drop the solution on the pending test surface, last, check whether the blue point appears or not within 30 seconds. If there are blue points on the filter paper, it is unqualified. Pay attention to that the test must be done after drying the pending test surface. After test, washing and cleaning the solution on the pending test surface.
The basic principle of blue point is that, if the passivation film is incomplete or contaminated by iron ion, chemical reaction will take place.
pendingFe2 + K[Fe(CN6)] = K[Fe(CN6)]↓dark blue + 2K

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