Getting Paid for Corrosion Protection: The Supplement Guide

The Corrosion Protection Gap

Corrosion protection is one of the most consistently underbilled operations in collision repair. Industry surveys suggest that fewer than 40% of shops bill for corrosion protection on structural repairs, even though OEM procedures require it on virtually every repair that involves welding, cutting, or exposing bare metal.

The reason shops don't bill for it is simple: it's easy to forget, it feels like a small amount, and many shops assume it's "included" in the labor time. It isn't. Every major estimating platform — CCC, Mitchell, and Audatex — lists corrosion protection as a separate, billable operation. And every major OEM requires it.

When Corrosion Protection Is Required

OEM procedures require corrosion protection in the following situations:

• Any repair involving welding (weld-through primer on weld flanges)
• Any repair involving cutting or grinding that exposes bare metal
• Any repair to structural components (rocker panels, pillars, floor pan, frame rails)
• Any repair that involves removing factory corrosion protection (seam sealer, undercoating, cavity wax)
• Any repair to areas that are exposed to moisture (wheel wells, door bottoms, rocker panels)

Types of Corrosion Protection Operations

There are several distinct corrosion protection operations, each of which is billable separately:

• Weld-through primer: Applied to weld flanges before welding to prevent corrosion at the weld joint. Required by virtually all OEMs.
• Seam sealer: Applied to seams and joints after welding to prevent moisture intrusion. OEM procedures specify the type and application method.
• Cavity wax / anti-corrosion compound: Injected into enclosed structural cavities (rocker panels, pillars) after repair. Required by many OEMs for enclosed sections.
• Undercoating: Applied to the underside of repaired panels to match factory undercoating that was removed during repair.
• Corrosion protection coating: Applied to bare metal surfaces in areas that are not painted (inside door skins, inside trunk lids, etc.).

Writing the Corrosion Protection Supplement

Your corrosion protection supplement should cite the specific OEM procedure that requires the operation. For example:

"Toyota Body Repair Manual, Section 5-2-4 requires application of weld-through primer to all weld flanges prior to welding and seam sealer to all welded seams after welding on structural repairs. The repair to the left rear quarter panel and inner rocker panel involves 14 weld flanges and 3 seamed joints requiring corrosion protection per the above procedure."

Also cite the relevant P-page from your estimating platform. CCC, Mitchell, and Audatex all have P-pages that explicitly list corrosion protection as a non-included, separately billable operation.