Valmont Coatings
One Valmont Plaza, Suite 400
Omaha, NE 68154-5215 USA
By Phone: (402) 963-4250

Duplex Coatings

Powder Coating or Painting over Hot Dip Galvanizing

Salvador Dali Museum

A duplex coating is formed by painting or powder coating over hot dip galvanized steel. When used together, the corrosion protection provided by the galvanizing and painting/powder coating is far superior to either protection system used alone. Many products, such as automobiles and radio towers, have utilized duplex systems successfully for decades.

How it works: In order to protect steel from corrosion, something must interfere with the corrosion cell, either by blocking the electrolyte (a medium for conducting ions: water) or by becoming an anode. Two common methods of corrosion protection are barrier protection (blocking the electrolyte from the steel surface) and cathodic protection (the formation of another anode). Hot dip galvanizing alone offers both types of protection; however, painting or powder coating over hot-dip galvanizing creates an additional barrier layer on top of the zinc coating.

Why use a Duplex System?

  • Easy Retouch: Paint and Powder Coatings may, in time, need to have small nicks or scratches touched up. This can be relatively inexpensive and easy to accomplish.
  • Color Coding & Safety: Duplexing increases safety in many environments by enabling color-coding of gas, steam, or chemical pipes, identifying hazardous work areas & walkways, and marketing high voltage electrical lines & equipment.
  • Extended Corrosion Resistance: In harsh environments where galvanizing, paint or powder coating alone has difficulty protecting steel, utilizing a duplex system can provide the necessary corrosion resistance.
  • Aesthetics: Hot dip galvanized steel provides an attractive, metallic-gray finish. When the industrial finish of galvanizing doesn't cut it, painting or powder coating can offer an aesthetic alternative.
  • Economic Benefit: Duplex systems provide tremendous economic advantages because of the extended time to first maintenance and delayed maintenance cycle. Initially, the cost of a duplex system is high because both corrosion protection systems must be paid for. However, because of the synergistic effect, the initial premium cost pays off over the life of the project and in the end is less expensive than coating bare steel.
  • Duplex Coatings are offered at the following Valmont Coatings locations