Abstract
This work was undertaken as part of a Seedling project funded by the Marine Energy Program within the DOE’s Water Power Technology Office. The goal of this work was to explore surface modification of commercial alloys to enhance their corrosion resistance in marine environments. Existing corrosion protection solutions such as painting/coatings, or using corrosion resistant materials, suffer from durability issues and/or are expensive. Therefore, laser surface processing (LSP) was proposed as an alternate, and a novel, corrosion protection technique that can potentially overcome the challenges of existing techniques.
Laser surface processing employs relatively low (~hundreds of mJ) energy laser pulses to locally modify the surface of the given material. In this project, LSP was used to surface modify test coupons of 6061-T6 aluminum (Al) alloy, low-carbon steel and 316 stainless steel. Benchtop, limited-term corrosion tests were performed on LSP-modified and un-modified samples and their respective corrosion behavior was analyzed through gravimetry, surface roughness measurements and x-ray photoelectron spectroscopy. Based on these tests, the key observations are:
- 6061-T6 Al shows up to ~15% improved corrosion resistance relative to non-LSP’ed samples.
- Low-carbon steel shows up to ~25% improved corrosion resistance relative to nonLSP’ed samples.
- Laser power used for LSP needs to be controlled to achieve the necessary corrosion protection of the modified surfaces.
These initial results show LSP to be a promising technique for corrosion protection, specially as it avoids the need for paints/coatings that otherwise can leach into the ocean. As LSP can be applied locally, and in a desired location without affecting the remainder of the material, its applicability at joints and welds, of components and structures should be explored. Additional effort is needed to fully understand the corrosion protection mechanism(s) in LSP’ed surfaces and to evaluate their performance in long-duration tests in marine environments. Determining the suitability of LSP for protecting large structures will also be valuable for marine energy applications.