Stainless steel is widely used in critical components of drinking water, wastewater, water reuse, and desalination treatment and conveyance systems. Contrary to popular belief, stainless steel can be prone to failures due to corrosion, including microbiologically induced corrosion (MIC). In fact, utilities have had issues with chloride and chlorine corrosion on 316 stainless steels, including well casings, process water piping, and castings at their desalination and water reclamation plants. Better construction and water quality-based material selection guidelines are needed as water purveyors rehabilitate their existing system and design their future water treatment facilities.
With the shortage of appropriate resources in mind, a team of fellow engineers and researchers specializing in identifying cost-effective approaches for advancing desalination methods has joined forces on a multi-layer project to develop stainless steel guidelines for water and desalination engineers. The United States Bureau of Reclamation (USBR) and the Water Research Foundation are jointly funding Guidelines for the Use of Stainless Steel in the Water and Desalination Industries, a project headed by California-based Carollo Engineers with the help of Consultancy Resources Corporation. The guidelines are an effort to help water industry professionals properly specify stainless steel materials and construction standards based on water quality considerations so that stainless steel corrosion can be avoided to the greatest extent possible.
Examining the Cost of Stainless Steel Failures
The desalination industry has experienced rapid growth over the last 10 years with an installed capacity increase of 240% increase worldwide. This growth corresponds to an increase in construction expenditures from approximately $30 billion to $75 billion per year globally, and out of this annual cost, around 15% is associated with the cost of stainless steel materials. The expenditures represent significant capital investments and include detailed up-front engineering and planning efforts.
Although the 150 types of stainless steel on the market today are all formulated with corrosion resistance in mind, these materials are not immune to failures, which can produce costly reliability and safety problems. These corrosion-related failures often occur when a utility selects the wrong type of stainless steel for a given application, if proper care is not followed during construction, or if corrosion-inducing changes are made to the process flows once the system is operational.
Keeping It Simple
While stainless steel corrosion is a significant problem in water treatment with desalination systems, there are no up-to-date guidelines for these specific applications. Water engineers are forced to rely on a patchwork of recommendations and guidelines from other industries and trade groups. Water, wastewater, and water reuse utilities require more thorough, comprehensive guidelines for future planned desalination installations. They need a set of guidelines that establish material application and construction standards for stainless steel based upon the water quality conditions and the materials used for water applications.
Ensuring the Project’s Success
As a whole, the project is designed to help the water and desalination industries to properly specify the type of stainless steel used for different applications based upon water quality considerations, identify appropriate construction standards that should be followed to help promote materials’ useful life in excess of 20 years, and recognize appropriate operating conditions in an effort to avoid stainless steel corrosion. The proposed guidelines–which will focus on benefitting the water industry as a whole–will cover a range of typical installation issues and conditions, allowing them to be widely applicable to stainless steel use in desalination and water treatment. This report will offer water professionals a comprehensive database to locate vital research, guidelines, and research–all in one place.This project functions across three phases. The first phase–which has already been completed–focused on characterizing what is known versus what is unknown regarding the causes and mitigation of stainless steel corrosion in water treatment and desalination systems. The report is scheduled to include a review of specification, management, handling, storage, and operational maintenance of stainless steel materials. It will also include descriptions of these materials and a review of how they are used in water treatment applications. The team of engineers will then go on to summarize and analyze water utility experiences with corrosion. This helped the researchers identify what additional data is needed to develop accurate, well-rounded guidelines.Phase Two will focus primarily on testing. Project engineers will isolate questions related to stainless steel corrosion and, from them, develop a testing protocol to collect new data to supplement existing knowledge. Then, testing will begin on multiple metal types and finishes under various conditions and samples will be collected at a certified metallurgical laboratory.In Phase Three, water industry–specific guidelines will be developed. This part of the project is scheduled to be performed later this year. The guidelines will be written in the form of a decision methodology that walks industry professionals through the decision process of specifying and operating water treatment and desalination systems so as to minimize stainless steel corrosion.
Return on Investment
The economic impact of corrosion nationwide is estimated to be $267 billion annually, or approximately 3.1% of the nation’s gross domestic product. The safety and reliability of water supplies across the nation depends upon the successful operation (and manageable cost) of water, reuse, and desalination plant infrastructure. The successful application of these guidelines would result in designs, specifications, and operating plans in water, reuse, and desalination plants that have stainless steel components, which are well-suited to their applications and are installed and used in ways that protect and preserve their integrity and functionality.
