What are the challenges of joining aluminum in automotive body construction?

Aluminum joining challenges: Surface oxide layer (high melting point, insulating) affects weldability; lower resistance makes spot welding more difficult (requires higher current, causes faster electrode wear); thermal conductivity conducts heat away rapidly; galvanic corrosion when coupled with steel; material is softer (limiting mechanical fastening options); and heat-treatable alloys can soften in HAZ. Solutions include: Self-pierce riveting (SPR), flow drill screwing (FDS), clinching, adhesive bonding, friction stir welding, and specialized resistance spot welding with electrode dressing. Multi-material bodies often use different joining methods for aluminum versus steel sections.