Investigating the role of LASER Surface Processing on Labscale Corrosion in AA6061- Summary Presentation of Results

This PDF contains a slide deck summarizing results from the DOE sapling project "Surface Modification of Alloys for Low-cost Corrosion Protection in Marine Environment," conducted at Pacific Northwest National Laboratory. The project evaluates laser surface processing (LSP) as a low-cost, coating-free way to improve the corrosion resistance of AA6061-T6, an aluminum alloy attractive for marine and hydrokinetic structures but prone to localized corrosion in seawater. The deck compares LSP-treated and untreated AA6061 surfaces using XPS depth profiling, surface roughness measurements, six-month immersion in 3.5 wt.% NaCl, potentiodynamic polarization with in-situ imaging, and ASTM G48 crevice corrosion testing in FeCl3.

Across these tests, LSP surfaces showed a thicker oxygen-rich surface layer, a more noble corrosion potential (about -765 vs. -787 mV vs SCE), shallower pits after long-term immersion (about 10 um without any intergranular corrosion in LSP AA6061 vs. 30 um with signs of intergranular corrosion in non-LSP 6061), and fewer deep pits after crevice testing. In-situ imaging showed that attack on the non-LSP samples tends to progress through pit initiation and growth accompanied by significant hydrogen evolution all over the surface whereas, LSP samples tends to start at the edges of the processed region and undercut the modified layer only under very high anodic overpotentials. The deck also benchmarks these results against published laser-treatment studies on other aluminum alloys, showing comparable or better corrosion potentials at much lower laser power.

The results presented in this PDF will be submitted to a journal for publication. We will upload the manuscript into MHKDR once it is accepted for publication.