Search Results for freshwater environment

This article describes the various environments affecting corrosion performance, corrosion protection, and corrosion control. These include freshwater environments, marine environments, and underground environments. The article provides information on corrosion in military environments and specialized environments, representing less-well-known environments with more limited applications.

This article discusses the environmental factors and kinetics of atmospheric corrosion, aqueous corrosion, and soil corrosion of carbon steels. It also provides information on corrosion in concrete and steel boilers.

Simulated service testing includes exposures of either structural components or test specimens in environments that are representative of many general service situations. This article discusses the selection criteria of test specimens and methods of assessing the corrosion effects. The ASTM International and NACE International standards that are directly or indirectly applicable to simulated service corrosion testing in water are tabulated. The article also describes the effects of variable concentrations of dissolved carbonates, such as calcium, magnesium, and/or sodium, in water on corrosion.

Corrosion of marine- and land-based infrastructure is of major concern and its control forms an important objective. Thermal spray coatings (TSCs) are widely used for corrosion protection. This article focuses on two types of TSCs: cathodic or noble coatings and anodic or sacrificial coatings. It describes the factors affecting the performance of sacrificial TSCs in atmospheric and immersion environments. The article provides information on the applications of sacrificial TSCs, non-sacrificial coatings, and sealants/top coats, and exemplifies the use of sacrificial TSCs on structures for corrosion protection.

This article focuses on the corrosion and deterioration of components on recreational and small workboats. It discusses the materials selection and corrosion control for the components. These components include hulls, fittings, fasteners, metal deck gear, winches, backing plates, lifeline supports, inboard engines, cooling systems, propulsion systems, electrical and electronic systems, plumbing systems, masts, spars, and rigging.

The corrosion processes of metals during burial are affected by environmental pollutants, other archaeological material, geography, microorganisms in the soil, vegetation, land use, soil chemistry, soil physical properties, and the presence or absence of water and air. This article discusses the key environmental variables that affect the corrosion of buried metal artifacts. These include water (including dissolved salts and gases), sulfate-reducing bacteria, pH (acidity), and potential (oxidizing or reducing capacity). The article contains tables that list some corrosion products identified on archaeological tin and pewter, lead, iron alloys, silver alloys, and copper alloys. It also discusses the corrosion problems after excavation and the techniques followed by archaeological department for conserving metal artifacts.

This article addresses the general effects of the composition, mechanical treatment, surface treatment, and processing on the corrosion resistance of aluminum and aluminum alloys. There are five major alloying elements: copper, manganese, silicon, magnesium, and zinc, which significantly influence the properties of aluminum alloys. There are organic coatings or paints that provide a barrier between a corrosive environment and aluminum surface. Inorganic coatings, including claddings, and enhanced oxides, such as anodized films, Boehmite films, and conversion coatings also help in corrosion prevention. The article assists in the information on selection of fabrication operations, as they play an important role in corrosion resistance.

The use of zinc in corrosion-protective coatings is due to its higher galvanic activity relative to that of steel. Pure zinc dust provides the best sacrificial protection to steel in a galvanic couple. Zinc-rich coatings can be subcategorized according to the type of binder material used, namely, inorganic and organic zinc-rich coatings. Common inorganic binders such as post-cured water-based alkali metal silicates, self-cured water-based alkali metal silicates, and self-cured solvent-based alkyl silicates, are reviewed. The article also compares inorganic and organic zinc-rich coatings, and discusses the concerns regarding zinc-rich coatings.

Cathodic protection (CP) is an electrochemical means of corrosion control widely used in the marine environment. This article discusses two types of CP systems: impressed current systems and sacrificial anode (passive) systems. It describes the anode materials used in these systems and the CP criteria. The article examines the design considerations and procedures involved in the CP of marine pipelines, offshore structures, and ship hulls. An illustration of sacrificial anode calculation is also provided.

Nickel and nickel-base alloys are vitally important to modern industry because of their ability to withstand a wide variety of severe operating conditions involving corrosive environments, high temperatures, high stresses, and combinations of these factors. This article discusses the mining and extraction of nickel and describes the uses of nickel. It discusses the categories of nickel-base alloys, including wrought corrosion-resistant alloys, cast corrosion-resistant alloys, heat-resistant alloys (superalloys), and special-purpose alloys. The article covers the corrosion resistance of nickel with the inclusion of varying alloying elements. It provides useful information on the behavior of nickel and nickel alloys in specific environments describes its corrosion resistance in certain acids, alkalis, and salts.

Selection of appropriate grades of steel will enable the steel to perform for very long times with minimal corrosion, but an inadequate grade can corrode and perforate more rapidly than a plain carbon steel will fail by uniform corrosion. This article describes the effect of chemical composition, heat treatment, welding, and surface condition on corrosion resistance of stainless steels. It discusses the various forms of corrosion and the important factors to be considered when selecting suitable stainless steel for application in specific corrosive environments.

Thermal spray coatings (TSCs) are surface coatings engineered to provide wear-, erosion-, abrasion-, and corrosion-resistant coatings for original equipment manufacture and for the repair and upgrading of in-service equipment. This article presents an overview of five thermal spray processes and the specific flame and arc spray processes used to preserve large steel components and structures. It describes the TSC selection guide and an industrial process procedure guide for applying aluminum and zinc TSCs onto steel.

This article discusses the environmental influences on protective coating films that can result in deterioration. These environmental factors can be classified into four groups: (1) energy: solar, heat; (2) permeation: moisture, solvent, chemical, and gas; (3) stress: drying and curing-internal stress, and vibration-external stress; and (4) biological influences such as microbiological, mildew, and marine fouling.

Paints and protective coatings are the most common means of protecting materials from deterioration. This article focuses on coating degradation that results from the environmental interaction with the coatings. The major environmental influences of the degradation include energy (solar radiation, heat and temperature variation, and nuclear radiation), permeation (moisture, solvent retention, chemical, and oxygen), stress (drying and curing, vibration, and impact and abrasion), and biological influences (microbiological and macrobiological).

This article discusses the general properties of ocean water and their effects on corrosion. It describes the major and minor features of the ocean water on corrosion, including the effects of variability, pollutants, and fouling organisms. Effects of water flow velocity on marine corrosion are also reviewed.

Cathodic protection is an electrochemical means of corrosion control in which the oxidation reaction in a galvanic cell is concentrated at the anode, which suppresses corrosion of the cathode in the same cell. This article provides a detailed discussion on the fundamentals and types of cathodic protection as well as their power sources and design considerations. The criteria for the cathodic protection and types of materials used in sacrificial anodes and impressed-current anodes are also discussed. The article provides examples selected for familiarizing the design engineer with the steps for selecting a specific corrosion control method.

This article focuses on the effects of microscopic organisms and the by-products they produce on the electrochemical corrosion of metals. The general characteristics of the microorganisms that facilitate their influence on the electrochemistry of corrosion are discussed. The industries most often reported as being affected by microbiological corrosion are listed, along with the organisms usually implicated in the attack. The article explains that the influence of organisms can be addressed successfully for a corrosion control program by using four types of evidence: metallurgical, microbiological, chemical, and electrochemical. It provides information on the microbiologically influenced corrosion (MIC) of irons and steels, passive alloys (austenitic stainless steels), aluminum alloys, copper alloys, and composites. The article reviews the formation of microbial biofilms and macrofouling films. It also describes the general approaches taken to prevent MIC.

This article describes the various factors that affect the extent of corrosion resulting from galvanic coupling. The factors include galvanic series, polarization behavior, and geometric relationship of metals and alloys. The article briefly discusses the various modes of attack that lead to galvanic corrosion of anodic members. It also explains the three electrochemical techniques of screening tests for predicting galvanic corrosion. The electrochemical techniques comprise of potential measurements, current measurements, and polarization measurements. The article provides a detailed discussion on the performance of alloy groupings. It concludes with information on various control methods that reduce or eliminate galvanic-corrosion effects.

This article addresses the forms of corrosion that contribute directly to the failure of metal parts or that render them susceptible to failure by some other mechanism. It describes the mechanisms of corrosive attack for specific forms of corrosion such as galvanic corrosion, uniform corrosion, pitting and crevice corrosion, intergranular corrosion, and velocity-affected corrosion. The article contains a table that lists combinations of alloys and environments subjected to selective leaching and the elements removed by leaching.

This article provides an overview of the identification systems for various grades of wrought stainless steels, namely, the American Iron and Steel Institute numbering system, the Unified Numbering System, and proprietary designations. It elaborates on five major families of stainless steels, as defined by the crystallographic structure. These include ferritic stainless steels, austenitic stainless steels, martensitic stainless steels, and precipitation-hardening stainless steels. The mechanism of corrosion protection for stainless steels is reviewed. The article examines the effects of composition, processing, design, fabrication, and external treatments on the corrosion of stainless steels. Various forms of corrosion, namely, general, galvanic, pitting, crevice, intergranular, stress-corrosion cracking, erosion-corrosion, and oxidation, are reviewed. Corrosion testing for; corrosion in atmosphere, water, and chemical environments; and the applications of stainless steels in various industries are also discussed.