Is a blue spot inspection required after the stainless steel pickling process is completed?
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Dear experts: Is it necessary to conduct a blue spot inspection after the stainless steel pickling process is completed? Is there any standard basis for this? Please advise.
It is recommended to conduct a blue spot inspection after the stainless steel pickling process is completed, to ensure that the surface cleanliness meets the required standards. Blue spot testing involves adding an appropriate amount of red dye to clean water, spraying it onto the stainless steel surface, and then wiping it with a white cloth; any blue spots that appear on the cloth indicate that the surface is dirty or covered with oxides. Regarding the standard basis, **the standard ‘Methods for Analyzing Chemical Composition of Stainless Steel’ specifies the criteria for evaluating the surface cleanliness of stainless steel, including various methods such as the blue spot test. In addition, the industry standard \"Acceptance Criteria for Surface Quality of Stainless Steel Products\" also sets evaluations and requirements for the cleanliness of stainless steel surfaces. -
It should be done, but there is no unified standard; there are several formulas for blue dot solution. In my opinion, the most lenient one is the one specified by ASTM A380, while the strictest one is the formula that uses hydrochloric acid