Common Paint Defects and Their Causes



Paint Defect-Pops

Pops

Description:

  • Small swelled area like a blister
  • Broken edge craters if the blisters burst
  • Pinpoint holes in finish


    • Causes:

  • Excessive film build traps the solvent which is released during flash or bake
  • Insufficient flash off time before baking


    • Linetec Preventative Measures:

  • Controlled application through SOPs and automated equipment prevents excessive film build
  • Adequate flash-off time
  • Multi-zone oven controls promote gentle temperature ramping


    • Paint Dfect - Metallic Inconsistency

    Metallic Inconsistency / Mottling

    Description:

  • Inconsistent flake orientation causing color variation, particularly when viewed at different angles


    • Causes:

  • Oil canning of substrate surface (slight convex or concave distortion)
  • Batch to batch paint variation
  • Insufficient agitation of paint
  • Inconsistent application techniques
  • Variations in paint film thickness
  • Part design may necessitate hand spray (returns, framing, recessed areas)



    • Linetec Preventative Measures:

  • Communicate oil canning potential with customer
  • Communicate with customer the effect of part design on painting requirements
  • All incoming and in-house blended paints are inspected for color match in Linetec's in-house color lab
  • In-process paint agitated for consistency
  • Controlled application through SOPs and automated equipment assures consistent finish and paint film thickness


    • Paint Defect - Adhesion Failure

    Adhesion Failure

    Description:

  • Flaking or peeling paint between the top coat and primer, or top coat and substrate


    • Causes:

  • Improper surface preparation
  • Painting over oil, grease or other contaminants
  • Improper paint cure



    • Linetec Preventative Measures:

  • Linetec's chemical pretreatment system includes a dedicated chemical technician, a 5-stage pretreatment system, electronic interlocking to prevent failures and strong participation from chemical supplier
  • Test samples submitted monthly for analysis and coating weight verification
  • Oven operation and controls to prevent under-curing


    • Paint Defect - Light Coverage

    Light Coverage

    Description:

  • Paint fails to fully hide the substrate surface to which it is applied


    • Causes:

  • Inadequate film build
  • Faraday cage effect




    • Linetec Preventative Measures:

  • Understand customer requirements including exposed areas, unexposed areas and general expectations
  • Apply basecoat with automated equipment on complex parts
  • Hand spray recessed areas to ensure coverage
    • Linetec's Method of Prevention
    Paint Defect - Color Inconsistency

    Color Inconsistency

    Description:

  • Inconsistent color from part-to-part or job-to-job


    • Causes:

  • Batch-to-batch paint variation
  • Poor agitation
  • Over backing / burnt material



    • Linetec Preventative Measures:

  • All incoming and in-house blended paints are inspected for color match in Linetec's in-house lab
  • In-process paint agitated for consistency
  • Oven operation and controls to prevent over backing or burning


    • Paint Defect - Rack Marks

    Rack Marks

    Description:

  • Unpainted or light coverage areas on a part due to rack location or contact with part


    • Causes:

  • Rack in direct contact with part prevents paint coverage
  • Rack close, but not touching parts, blocks paint and creates light coverage in areas behind the rack
  • Excessive paint build-up on rack can soften in the oven causing the part resting on it to "sink in" creating a blotchy build-up when removed



    • Linetec Preventative Maintenance:

  • Understand customer requirements and expectations
  • Innovative rack designs minimize rack contact and interference
  • Utilize "racking recipes" to ensure consistent racking of each part
  • Rack maintenance schedule ensures that clean racks with minimal build-ups are used


    • Paint Defect - Wet Mil Marks

    Wet Mil Marks

    Description:

  • Small indentations on exposed surface, approximately 1 1/2" total width


    • Causes:

  • Marks are necessary result of taking "wet mil" measurements
  • Wet mil measurements are used to determine the wet mil film thickness of an applied coating. In turn, this is used to estimate the resulting dry mils. This testing is done in an effort to ensure adequate wet mill coverage to yield the required dry film thickness


    • Linetec Preventative Maintenance:

  • Controlled application through SOPs and automated equipment ensures consistent paint film thickness, thus reducing the required frequency of wet mil testing
  • After taking a wet mil reading, a hand-spray sweep is performed to cover and minimize the testing marks
  • Utilizing a newer style wet mil gauge with smaller profile designed to minimize the surface disruption







    • PDF copy of Common paint defects, their causes and Linetec's method of prevention