440A Stainless Steel, Laser Marking, Passivation and Rust

A. If these medical devices are not required to be sharp, they can be passivated with strong film by high-voltage technology. Steel can become a little yellow if you desire the passivating film to be thick.

A. The reason for rusting in the laser marked areas is that an insoluble oxide of some kind has been formed that does not allow the acid to see the substrate. Remove the oxide before passivating and all will be well.

A. Depending on quantities you can laser mark with Cermark or Thermark. The ceramic based solution is fused to the metal by low powered laser (CO2, Galvo ...) You will obtain a super crisp and very black mark. Both companies working on other colors for metal marking as well.

We use this method for underwater equipment. It is also used for marking of pacemakers and other medical products. Due to the process of applying the paint, drying time and laser time you will have to evaluate the efficiency for your application. For general passivation of stainless after welding we use phosphoric acid which might be referred to as white passivation.

A. I've had the same problems on some of my 440c medical reamers. It appears that the laser marking stays under the passivation and causes little rust spots after sterilization. We solved the problem by passivating before engraving, laser marking afterward, and white passivating them at last. After those treatments, not one of our other instruments rusted.

A. My name is Qasim Raza and I am from Pakistan. We are a manufacturing company of beauty care stainless steel products. I would like to tell you something about that what is Passivation.

Passivation is a special process we do during manufacturing to avoid rust.

For Passivation we dip instruments in boiling water mixed with some special liquid/chemical. Then the instruments boiled for 24 hours and after this we allow all the instruments to cool itself in the same water. The cooling process will take more the 12 hours.

After this we check all the instruments very carefully and if we find any problem in the instrument we remove it and finally send it to other manufacturing process.

I hope this stuff will help you to understand about Passivation. if any one have any question please let me know.

Best personal regards,

A. Hi Kerma. I don't think this can be done. "Brushing" is actually done with sandpaper/scotchbrite, and it physically removes the metal and the laser marking along with it. It is theoretically possible to not brush the engraved area, but that sounds impractical in reality. I think you will need to do the engraving after the brushing.

Regards,

A. I'm not 100% sure of what your problem really is? Ted covered some ground, but surface finishing is a matter of degrees. Meaning, depending on the energy application and or force used you can achieve different results. Another factor is the size and shape of the part and the hardness of the material. Not know the particulars, it is hard to make a good recommendation.

A. Production is not always set up after the most correct chemical point of view. Newer the less stains from laser markings can be removed either with spot passivation or if heavy stains, do some spot pickling before passivation.

Do remember that the purpose of laser marking might be to make dark colored marking and those marking are a thicker layer of chromium oxide. Try for instance to make a test.
You will not find free iron.

A. Sometimes, the entire work piece is to big for the process tank, and one will choose only to treat the "problem"; that is known as spot pickling or spot galvanizing, tampon plating, and probably many other names.