Since 1984, tin plated EMD pistons have been used in all 16-1 compression ratio turbocharged engines. The tin plating of piston skirts improves the reliability of break-in, reduces scuffing and adds to overall performance.
Tin is very soft and malleable and is very sensitive to superficial dirt cutting.
Scratches or mars must not be used as a criteria for scuffing. As a reminder, superficial dirt cuts, scratches and polished areas are not cause for piston removal.