Objective:

The project will work with a stakeholder team to:

  • Establish a credible testing protocol to assess base metal, heat-affected zone (HAZ), and deposited filler metal susceptibility to reduced properties associated with Zn-rich coatings.
  • Generate data to understand the relative impacts of Zn-rich coatings on high strength steel.
  • Develop a list of alternative coating systems and appropriate areas of application will be generated to promote the advantages of adopting Zn-rich coatings.
  • Provide recommendations for shipyard and Navy consideration.

Summary:

The project will evaluate the effect that Zn-rich coatings have on high strength structural steels, such as HY-100 and HSLA-100.  In shipbuilding, Zn-rich coatings are often avoided on high strength steels during any phase of the build process due to concerns of hydrogen embrittlement, particularly in the heat affected zones of welds.  However, there are several research papers suggesting that zinc primers do not induce hydrogen embrittlement in alloys of this yield strength.  Zn-rich coatings provide added corrosion resistance during construction as the various components tend to stay in lay-down areas for extended periods of time. The use of Zn-rich coatings can aid in reducing rework associated with repairing pitted or rusted steel.  Additionally, in the case of inorganic Zn-rich coatings, their high tolerance to heat can allow a reduction in the amount of coating removal prior to hot work applications like cutting and welding.

Key Deliverables / Benefits:

Use of Zn-rich coatings as a pre-construction primer or primer for future coating systems has several benefits.

  • In shipbuilding, steel components can lie unused for months, if not years, prior to final coating application and assembly. The use of Zn-rich coatings provides additional corrosion protection during this downtime and prevents excessive remediation efforts for rust and pitting corrosion that can occur. In many cases, these same zinc coatings can be retained and further top-coated, providing a complete coating system that provides galvanic protection along with the traditional barrier marine coatings provide.
  • Given that many inorganic Zn-rich coatings have a significantly higher thermal stability compared to organic coatings, a reduction in the amount of coating removed to perform hot work could result. This could be a substantial benefit to new construction shipyards, as less labor would result from removing coating for cutting and welding. Additionally, the reduction in coating removal for hot work yields additional structural coverage downstream of the coating removal processes, resulting in less steel corrosion.  Finally, in situations where the Zn-rich coating can be retained as part of a final coating system, additional labor savings would result from not having to restore a steel surface to near white metal prior to applying the final coating system.

Point of Contact:

Eric Shoyer | Elzly Technologies | eshoyer@elzly.com

Overview

Surface Preparation & Coatings

Project Team:

  • Elzly Technologies, HII-Newport News Shipbuilding

March 2023 – February 2024

NSRP INVESTMENT $150K