Galvanizing vs. Paint Systems

While some people may have the misconception that zinc-rich paint provides the same level of protection as hot-dip galvanizing, there is little comparison in terms of corrosion performance, sustainability and lifespan.

The below charts outline the measurable and significant benefits of hot-dip galvanizing versus inorganic zinc-rich paint.

Requirements / Characteristics Hot-Dip Galvanized Steel Inorganic Zinc-Rich Paint
Special Handling No Paper interleave, cloth slings, wood separators
Field Touch-Up No Required
Application Factory Field or factory
Weather Dependent No Yes
Temperature Range -75F to 392F <200F
Corrosion Protection Cathodic & barrier Barrier
Hardness/Abrasion Resistance 179 to 250 DPN Varies by type
  • Service Life/Durability (a)
    Requirements / Characteristics Hot-Dip Galvanized Steel Inorganic Zinc-Rich Paint
    Rural >100 years (b) 27 years (c)
    Urban 90 years 17 years
    Industrial 70 years 12 years
    Marine 50 years 12 years

    (a) To 5% rust on substrate steel
    (b) Zinc Coating Life Predictor, Zhang, 2001
    (c) NACE Paper 06318, Helsel, Melampy, Wissmar, 2006

  • Coating
    Requirements / Characteristics Hot-Dip Galvanized Steel Inorganic Zinc-Rich Paint
    Thickness Exceeds ASTM A 123 minimum (> 3.9 mils for 1/4” thick steel) Variable - may not meet required minimum due to lack of skill
    Coverage Exterior & Interior Exterior surfaces only
    Consistency Edge & Corner thickness ≥ flat surfaces Edge & Corner thickness < flat surfaces
    Cathodic Protection Zinc metal is anodic to steel Maybe - Zinc % may be too low for conductivity/Binding materials may not be conductive, minimizing cathodic protection
    2000 Hour Immersion Test No base steel corrosion Paint absorbed water & underfilm corrosion of the substrate steel occurred
    Ultraviolet Ray Exposure No effect on performance No severe degradation
    Abrasion Resistance Alloy layers are harder than base steel
    (DPN hardness ranging from 179 - 250)
    Moderate; DPN hardness approximately 33% less than HDG
    Performance Range Testing -100 C to 350 C Deterioration at 250 C
  • Application
    Requirements / Characteristics Hot-Dip Galvanized Steel Inorganic Zinc-Rich Paint
    Surface Preparation Documented, timed, scientific sequence Function of human expertise, intolerant of improper cleaning/profiling
    Procedure Observable completion of metallurgical reaction Constant agitation of mixture, regulation thickness & drying time per pass
    Application 24/7/365 - all weather Requires specific temperature conditions
    Bond Strength to Steel ~ 3600 psi ~ 600 psi
    Size Range of Products 90’ - 120’ long by 6’ - 8’ wide/deep Unlimited

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The American Galvanizing Association, “Hot-Dip Galvanized Steel vs. Zinc-Rich Paint”, www.galvanizeit.org