Aluminum Trailer Crossmember Repair: Welding Cracked Crossmembers

This is a recent aluminum welding job from our shop in Zion, IL. The crossmembers on an aluminum trailer had cracked where they join the main rail. We prepped the cracked joints and welded them back to the rail.

Why Trailer Crossmembers Crack

• Years of road vibration and flex that fatigue the metal at the welds
• Heavy point loads and overloading
• Forklift traffic on the trailer floor
• Corrosion where aluminum touches steel fasteners or brackets
• Earlier repairs that were welded over a crack without proper prep

Signs to Look For

• Visible cracks at the weld or where the crossmember meets the rail
• A floor that sags, flexes or makes noise under load
• Loose or broken floor fasteners
• A broken crossmember noted during a DOT inspection

Small cracks spread. Fixing one joint early is much cheaper than replacing a run of crossmembers or a damaged floor later. If you are due for an inspection, see DOT inspections.

Why Aluminum Welding Is Different

Aluminum is not welded like steel. It is covered by an oxide layer that has to be removed, and it pulls heat away fast. If a crack is just welded over, it usually comes back next to the new weld. Our process:

1. Find the full length of the crack.
2. Grind the crack out and clean the metal down to bare aluminum.
3. Weld with aluminum filler and the right heat for the thickness.
4. Inspect the finished weld, and add a reinforcement plate or replace the section if the original metal is too weak.

Repair or Replace?

If the crossmember itself is sound and only the joint is cracked, welding is the fastest and cheapest fix. If the crossmember is bent, badly corroded or cracked in several places, replacing that section is the better long-term repair. We tell you which one it is before we start. We also weld steel frames, aluminum fuel tanks and trailer parts. See welding & fabrication and trailer repair.