Dear Dr. Ajmal T.S. ,

It might be possible that when you increasing laser power you induce chemical and morphological surface phenomena on steel (as during welding and other thermo processes for material manufacturing). Essentially the thermal processes could cause the formation of carbides (or other compounds) and surface defects (as pores, molten pool boundaries, surface roughness and anisotropy) , which locally alter the formation a protective and homogeneous passivation film and hence reduces the corrosion performance. At lower laser power, perhaps, you could try to restore the corrosion performance.

For more details, please see:

-Laser Materials Processing for Improved Corrosion Performance

By Ryan Cottam

In book: Environmental and Industrial Corrosion - Practical and Theoretical Aspects (2012)

Available at: https://www.intechopen.com/books/environmental-and-industrial-corrosion-practical-and-theoretical-aspects/laser-materials-processing-for-improved-corrosion-performance

and

-Corrosion of metallic materials fabricated by selective laser melting

Kong, D., Dong, C., Ni, X. et al.

npj Mater Degrad. 3, 24 (2019)

Available at: https://www.nature.com/articles/s41529-019-0086-1

Best regards, Pierluigi Traverso

Thank you, Dr. Pierluigi Traverso.

I did laser surface melting on those samples.

Thank you for the answer and suggested reading links.

Dear Dr. Ajmal T.S. ,

thank you very much for the information. From the accompanying literature you will see that I had imagined that it used the indicated process. Allow me to suggest to carry out a chemical and morphological analysis (possibly also metallographic) of the samples obtained according to the different laser energies. In conjunction with the corrosion data, I would say you could get an interesting and good-quality paper out of it.

Good job and best regards. Pierluigi Traverso