Commercial Vehicle Structural Parts

Weathering and structural protection for long-term road service

Commercial vehicle structural parts include exposed body brackets, steps, cargo bodies, side panels and other structures. Transport vibration and outdoor exposure place strict requirements on super-durable weatherability and mechanical strength.

Veri Coating offers super-durable polyester-HAA smooth powder with at least 90% gloss retention after 1,000 hours of xenon-arc exposure, meeting Qualicoat Class 2 requirements and passing 1,000 hours of acidic salt-spray testing.

Application notes: Welded and heavy structures require careful control of edge coverage and temperature, and an epoxy primer may be used where the corrosion environment is more severe.

Typical Powder Coating Challenges for Commercial Vehicle Structural Parts

Corrosion Failure at Welds and Edge Weak Points

Low film build at welds, cut edges, sharp edges and lap joints combines with slag, mill scale and oil that weaken pretreatment, causing these areas to blister and rust first before corrosion spreads onto flat surfaces. High humidity, salt spray and road de-icing salts accelerate failure.

Formulation Design

Use an epoxy powder primer with stronger edge coverage and corrosion resistance, with a weatherable polyester topcoat where necessary.
Optimise powder reactivity, melt viscosity and particle-size distribution to improve continuous coverage on sharp edges.

Process Control

Remove slag, spatter and mill scale after welding and round sharp edges.
Pre-coat welds, inside corners and edges before completing the overall application.
Check grounding, voltage and gun distance to prevent the Faraday cage effect and back ionization.

Validation Focus

Film-thickness difference between sharp edges and flats
Scribed salt spray
Weld-area adhesion
Corrosion-creep width

Uneven Cure and Stress Cracking in Heavy ComponentsCure-related cracking requires correction of the cure profile from actual part temperature.

Uneven Cure and Stress Cracking in Heavy Components

Thick plate, castings and large welded assemblies heat slowly and have large differences in thermal mass. Judging cure only by oven temperature and time can leave local undercure, while a longer bake can overbake thin sections. Temperature gradients, residual welding stress and coating brittleness can then combine to cause cracking and adhesion loss.

Formulation Design

Select a 140–160°C low-bake system suited to the line capability to widen the effective cure window.
Balance reaction rate, flexibility and adhesion to reduce sensitivity to stress caused by temperature differences in heavy components.

Process Control

Use an oven profiler to measure part-temperature curves at the thickest and thinnest locations.
Use infrared preheating or zoned temperature control to reduce temperature differences across sections.
Determine cure from effective dwell after the part reaches the specified metal temperature.

Validation Focus

Heat-up profile at the thickest location
Effective dwell time
Crosslinking/solvent rub
Thermal cycling and cracking