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Construction Machinery

Weathering, corrosion and mechanical protection for heavy-duty service

Construction machinery includes structural parts for excavators, loaders, cranes and other large equipment. These components remain outdoors and are exposed to soil abrasion, rain and ultraviolet radiation, so the coating must provide weatherability, corrosion protection, adhesion and mechanical performance.

Veri Coating offers heavy-duty anticorrosive systems with more than 1,000 hours of salt-spray resistance and C4-C5 protection levels, as well as super-durable systems with at least 90% gloss retention after 1,000 hours of xenon-arc exposure and Gt0-1 adhesion. At the same performance level, TGIC systems offer a greater cost advantage.

Application notes: Castings should be preheated to release moisture, while welds, edges and heavy workpieces require adequate powder coverage and confirmed curing temperature.

Typical Powder Coating Challenges for Construction Machinery

Corrosion at Corners and Sharp EdgesLow film build at sharp edges requires better edge deposition and a complete primer/topcoat system.

Corrosion at Corners and Sharp Edges

Cut edges, formed edges and welds on construction machinery are often the first areas to blister and rust. A small edge radius, uneven pretreatment coverage, electrostatic shielding and coating pull-away during melt flow can leave effective film thickness below that on the main surface, creating preferential corrosion sites.

Formulation Design

  1. Optimise powder reactivity, melt viscosity and particle-size distribution to improve edge build and continuous coverage.
  2. For highly corrosive service, use a pure epoxy powder primer with strong edge-wrap capability beneath a weatherable polyester topcoat.

Process Control

  1. Deburr and, where possible, round sharp edges, ensuring continuous degreasing, rust removal and phosphate conversion coating.
  2. Adjust local voltage, gun distance and spray angle, and pre-coat or touch up formed edges, welds and spray shadow areas.
  3. Confirm the cure window from actual part temperature to prevent undercure or excessive flow from thinning edges again.
Validation Focus
  • Film-thickness difference between edges and flats
  • Pretreatment-layer integrity
  • Corrosion creepage after scribed salt spray
  • Intercoat adhesion between primer and topcoat
Low Cure Efficiency on Heavy-Gauge ComponentsHeavy parts heat slowly; use a low-bake system and establish the cure profile from actual part temperature.

Low Cure Efficiency on Heavy-Gauge Components

Thick steel plate, castings and large welded assemblies have high thermal mass, causing a marked heat-up lag between the surface and core. Judging cure only by oven temperature and nominal time can leave local undercure, poor adhesion or hardness variation; simply extending the bake reduces throughput and increases energy use.

Formulation Design

  1. Select a 140–160°C low-bake polyester system for the required weathering class to shorten dwell after the part enters the effective cure window.
  2. Balance reactivity and the flow window to achieve complete crosslinking and stable appearance at the lower temperature.

Process Control

  1. Use infrared preheating to raise surface temperature quickly, followed by forced hot-air circulation to heat the interior and reduce temperature gradients.
  2. Adjust zone temperatures, air velocity and dwell time for section-thickness variation, load density and hanging orientation.
  3. Use an oven profiler to establish a dedicated heat-up and dwell profile based on actual metal temperature at the thickest location.
Validation Focus
  • Heat-up profiles at the thickest and thinnest locations
  • Effective dwell after reaching target metal temperature
  • Hardness, adhesion and impact performance by location
  • Throughput, specific energy use and batch repeatability