We currently laser etch stainless steel (17-4) for medical applications. After laser etching, we follow with Type II nitric acid passivation at ambient condition/temperature. The intent of the passivation is to remove free iron from laser etched area, which could create a rusting issue if left in nonpassive state.
In an attempt to reduce hazards and flexibility, we are looking at citric acid passivation per ASTM A-967. In testing, we are noticing that the citric acid is not as effective as the Type II nitric acid passivation on the laser etched areas. The laser etched areas don't pass the copper sulfate test. We have had some samples that have passed the copper sulfate test, but the laser etch is completely removed.
Here are my questions. Has anybody dealt with this issue before? Is it possible to achieve success with citric acid passivation of laser etch? If so, then how is then done in a way not to completely remove the laser etch? Is there an adititive used like a mixed acid blend to have success? You input is appreciated.
In an attempt to reduce hazards and flexibility, we are looking at citric acid passivation per ASTM A-967. In testing, we are noticing that the citric acid is not as effective as the Type II nitric acid passivation on the laser etched areas. The laser etched areas don't pass the copper sulfate test. We have had some samples that have passed the copper sulfate test, but the laser etch is completely removed.
Here are my questions. Has anybody dealt with this issue before? Is it possible to achieve success with citric acid passivation of laser etch? If so, then how is then done in a way not to completely remove the laser etch? Is there an adititive used like a mixed acid blend to have success? You input is appreciated.
