Guide Highlights Product Choice for Duplex Coatings


The Galvanizers Association of Australia recently released a product recommendation guide for coating galvanized steel to prevent paint delamination and corrosion.

The painting of hot dip galvanized steel, often referred to as duplex coating, provides increased durability and chemical resistance. The new Duplex Coatings-Paint Product Guide is a supplement to GAA’s previously published Guide to Paint Systems for Hot Dip Galvanized Steel in Atmospheric Service (Duplex Coatings).

“About once a month we come across issues in duplex coatings where either the surface preparation wasn’t correct, or the wrong paint system was used for that environment. It happens more often than you’d think,” said Ann Sheehan, Corrosion and Sustainability Officer for GAA

According to the GAA, since the zinc layer of galvanized steel is so reactive, it is important to select the best paint system and properly prepare the surface, or corrosion can actually be accelerated and reduce the overall service life of the steel.

In their Guide to Paint Systems, GAA recommends three main steps to select the right paint to apply to a hot dip galvanized structure:

  • Identify the environment;
  • Determine the service life required for the painted structure; and
  • Select the appropriate painting system from the Service Requirement Guide.

The new product guide outlines recommended paint companies, advised surface preparations, first coat options and second coat options for the different service requirements of galvanized steel. It also lists the atmospheric corrosivity category, with years to first maintenance of paint component of the duplex system, from the Standard AS/NZS 2312 Part 2.

“Engineers and specifiers often ask us for recommendations around which paint products to use for a particular system. We decided to save the industry some time by sourcing that information direct from paint suppliers and grouping them within service requirements and environments as laid out in AS/NZS 2312 Part 2,” Sheehan said.

“While more people might be aware of popular paint manufacturers, the guide also introduces a range of other manufacturers that specialize in industrial protective coatings. This helps our members to find the best fit for their next duplex coating project, no matter where it might be located.”

GAA notes there may be suitable alternatives that are not outlined in the recommended guide, and for service requirements that need to meet specific industrial chemical or solvent exposure requirements, paint manufacturers should be contacted directly. The companies’ contact details can be found in the back of the product guide.

Both GAA guides are available for free download with a registered email on the GAA’s technical publications page.

Corrosion Prevention in Australia

Earlier this year, the Australasian Corrosion Association released its "Impact of Corrosion in Australasia" report, estimating that the country could spend up to roughly $78 billion per year on the management and mitigation of corrosion on its national infrastructure assets.

The report, which was commissioned by Resona, investigated corrosion’s impact on the nation and cited research from NACE International (now part of AMPP: the Association for Materials Protection and Performance). The data was assessed using a Net Present Value approach based on three stages, including:

  • Determination of the cash flow for corrosion related activities;
  • Calculation of the present value of the cash flow; and
  • Calculation of annual equivalent rates.

According to the report, corrosion effects can contribute between 3.5% to 5.2% of global domestic product and is most commonly caused by water, carbon dioxide and hydrogen sulfide, but can also be aggravated by microbiological activity. In its report, Resona extrapolated these figures to reach its high estimate of $78 billion per annum on corrosion-affected asset remediation.

For New Zealand, the company found an estimated impact for corrosion costs to be NZ $16 billion, and globally, found that between $375 billion and $875 billion could potentially be spent on corrosion.

However, in the oil and gas industry, these effects can be even more costly, attributing to more than 7%, which equated to more than $20 billion (in Australia alone) in 2013. Other sectors prone to corrosion-related issues include water and wastewater, construction and infrastructure, as well as defense, automotive and agricultural sectors.

“The UK’s Energy Institute ranks corrosion as the second most frequent cause in initiating loss of hydrocarbon containment in offshore platforms,” the report stated. “Calculation of the costs of any of these components is complex … For example, the cost of corrosion inhibitors is inherently complex.

“The cost of installation and maintenance of injection equipment, inhibitor chemical(s), monitoring inhibitor concentration(s), system changes to accommodate the inhibitor, system cleaning, waste disposal and personnel safety equipment, must be factored into any economic evaluation of the use of corrosion inhibitors.”

Other cost factors include the potential loss of the product and indirect costs, such as operation shutdowns, maintenance and labor.

Looking to the future, the report also stated that new techniques for early detection of corrosion were in development, and that the Gorgon Project in Western Australia was an example of a holistic approach where whole-of-life construction and projected maintenance costs were taken into account.

A copy of the full report can be viewed here.


Tagged categories: Asia Pacific; Coating Application; Coating Materials; Coatings; Corrosion; Corrosion protection; Corrosion resistance; Duplex coatings; EMEA (Europe, Middle East and Africa); Galvanic corrosion; Galvanized steel; Galvanized/thermal spray coatings; Hot-dip galvanizing; Latin America; North America; Paint application; Surface preparation; Surface Preparation; Z-Continents

Join the Conversation:

Sign in to our community to add your comments.