Yes. LIBS is very much a surface technique so any surface contamination would be included with the plasma and affect the results. For that reason, the KT-100/100S analysis time includes 1 second of Drill Down by default to improve data quality. For heavy corrosion or other contamination, it is recommended to use a grinding medium to remove the surface layer until you can see the base metal.
Laser-Induced Breakdown Spectroscopy (LIBS)