Specifying Products for Highly Corrosive Environments


The stakes are high when specifying products for highly corrosive environments. Beyond costly product failures, catastrophes can ensue, some even resulting in human harm.

The total cost of corrosion in the United States has been estimated at approximately $276 billion/yr,1 a staggering figure that underscores the inherent economic dangers caused by improper product specification and resulting product failure. The corrosion costs for drinking water and sewer systems alone amounts to approximately $36 billion/yr (see Figure 1).

Those who study corrosion and the dramatic implications of the damage it causes concur that:

  • There is a misconception that nothing can be done about corrosion; to the contrary, the specification of optimum anticorrosive products provides opportunities for tremendous cost savings.

  • Sound corrosion management, built upon proper product specification, depends on a comprehensive understanding of regulations and standards.

  • Product life predictions and performance assessment methods are essential for determining what products will perform well over time.


For years, all available brands of PVC-coated galvanized conduit met exactly the same UL 6 standards and carried an identical UL Mark relating to safety conformance. Yet, it was apparent in the marketplace that not all brands performed the same.

In 2005, the ETL SEMKO division of Intertek, an independent testing, inspection, and certification organization, evaluated PVC-coated galvanized conduit brands not for safety issues, but for product performance and longevity as tested under conditions consistent with highly corrosive environments. The results established that some of these products, previously viewed as equal by way of UL certification, were in fact far from equal in terms of meeting ETL-Verified performance standards.

The testing began in December 2004 and ended in July 2005; specimens from four sources were tested. Performance was assessed based on how the products performed when:

  • Immersed in boiling water (according to the intent of ASTM D 870, Standard Practice for Testing Water Resistance of Coatings Using Water Immersion)

  • Exposed to heat and humidity (according to the intent of ASTM D 1151, Standard Practice for Effect of Moisture and Temperature on Adhesive Bonds; and ASTM D 4585, Standard Practice for Testing Water Resistance of Coatings Using Controlled Condensation).

Heat and humidity testing was selected for several reasons:

  • Heat and humidity are universally accepted in the coating industry as standard parameters for evaluating how well a coating protects against corrosion. Standard test procedures are documented and recognized

  • Heat and humidity are widely acknowledged as corrosion-accelerating agents

  • Heat and humidity are typical conditions in coated conduit application environments

  • Heat and humidity chambers are available as standard equipment for testing

  • Heat and humidity testing in the laboratory provides a method that, when combined with real-time exposure, can be used to predict the product's lifecycle in corrosive environments.

Adhesion was evaluated in accordance with the procedures outlined in Section 3.8, Adhesion, of NEMA Standards Publication RN 1, PVC Externally Coated Galvanized Rigid Steel Conduit and Intermediate Metal Conduit. Section 3.8 describes how to conduct the adhesion test; however, it has no associated performance requirement other than that the PVC tear before separation from the metal substrate.

The results of both tests confirmed significant differences in adhesion performance of the four brands examined, and help explain why only certain brands carry the ETL Verified Mark.


There are no performance requirements for coated conduit in existing standards; however, committees that develop conduit standards are currently considering performance testing. In the meantime, the best course of action while specifying products for highly corrosive environments is to select those that carry an independent product testing label such as the ETL Verified Mark. The reason is built upon solid empirical facts: First, all available brands of PVC-coated galvanized conduit meet exactly the same UL 6 standard and carry the same UL Mark relating to safety conformance. However, only the brands that also have passed the ETL testing requirements are authorized to carry the ETL Verified Mark as well.

To obtain the ETL Verified Mark, a manufacturer provides an initial qualification sample to Intertek. The sample is then independently tested to the specifications of the appropriate standard. If the sample meets the requirements, an Intertek field representative will visit the manufacturer's facility to independently select a final qualification sample for further testing. If the second sample meets performance requirements, the manufacturer may use the ETL Verified Mark for the product. The manufacturing facility is then subject to quarterly audits to ensure ongoing compliance.

ETL testing, and consequently ETL verification, is based on actual product performance as a predictor of reliable service life. Brands that carry the ETL Verified Mark have a documented, proven ability to perform in a corrosive environment over an extended period of time—a fact that has been evaluated and confirmed by a world-recognized, independent, third-party source. Specifying tested and verified products will go a long way toward ensuring successful performance in the field and avoiding the high cost—and sometimes disastrous effects—of product failure.


The ability to successfully combat the high costs of corrosion demands an awareness of how varying products resist corrosion damage, which are most effective, and why. Proper specification requires that all applicable standards for evaluating anti-corrosion performance are thoroughly understood. Knowledge-based decision-makers require comprehensive, quantitative methods to compare the relative performance of products. Objective evaluations, such as those required to achieve ETL-Verification, provide an important foundation for effective specifications, i.e., reliable product-life projections and performance assessment.

  1. “Corrosion Costs and Preventive Strategies in the United States.” Report by CC Technologies Laboratories Inc. to Federal Highway Administration, Office of Infrastructure Research and Development, Report FHWA-RD-01-156, September 2001.

Author Information
Martin is principal of Henry Martin Consulting LLC, Metairie, La. He has more than 40 years of engineering experience in both the private and public sectors, including the design and inspection of electrical systems for commercial spaces, institutions, industrial and municipal plants, and utilities.

Choosing the right material

Selecting the best anticorrosion products and applying them in the most effective ways begins with an in-depth conversation with the client, who can help you determine how important reliability is to the production and profitability of his or her operation. After the mechanisms of corrosion in the environment are defined, consider the material as much as the design itself. Choosing the wrong material can result in frustrating, or even dangerous, situations.

Defining the corroding agents and determining the concentration can be a complex process. Several corrosive elements usually are present, and interactions are not always well documented. Water is the most common corrosive element and usually is present to some extent in every enclosure application. Adjacent processing operations or other intermittent activities, such as industrial cleaning and the general plant environment, may expose the enclosure to a variety of corrosive agents and temperatures. Each environment is unique, so identify all possible corrosive agents for the intended application.

Metal corrosion is influenced by surface finish, surface treatment (such as painting or galvanizing), and use of materials such as stainless steel or composite fiberglass materials, which are naturally corrosion-resistant. Aluminum, for example, should not be used in high-mineral acid environments. Stainless steel should not be used in applications exposed to high levels of salts. Some of the preferred methods of controlling corrosion are by material selection, alteration of the environment, design changes, and coatings. The most common and cost-effective corrosion protection method for metal used throughout the world is coatings.

The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
Pipe fabrication and IIoT; 2017 Product of the Year finalists
The future of electrical safety; Four keys to RPM success; Picking the right weld fume option
A new approach to the Skills Gap; Community colleges may hold the key for manufacturing; 2017 Engineering Leaders Under 40
Control room technology innovation; Practical approaches to corrosion protection; Pipeline regulator revises quality programs
The cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Power system design for high-performance buildings; mitigating arc flash hazards
VFDs improving motion control applications; Powering automation and IIoT wirelessly; Connecting the dots
Natural gas engines; New applications for fuel cells; Large engines become more efficient; Extending boiler life

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
The maintenance journey has been a long, slow trek for most manufacturers and has gone from preventive maintenance to predictive maintenance.
This digital report explains how plant engineers and subject matter experts (SME) need support for time series data and its many challenges.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.
Maintenance Manager; California Oils Corp.
Associate, Electrical Engineering; Wood Harbinger
Control Systems Engineer; Robert Bosch Corp.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me