Search Results for immersion coatings

Organic coatings are the principal means of corrosion control for the hulls and topsides of ships and for the splash zones on permanent offshore structures. This article describes surface preparation which is the most important consideration in determining the performance of organic coating systems. It contains a table that lists the uses and applicable standards for various surface preparation techniques. The article provides information on organic coatings in topside coating systems and reviews the importance of primers in the protection of steel substrates. It also explains the property requirements and the common types of immersion coatings.

Aluminum components are often plated with other metals to mitigate the effects of corrosion and wear, improve application performance, and extend service life. This article discusses some of the more common aluminum plating processes, including electroplating, immersion plating, and electroless plating, and describes various plating materials and the types of applications in which they are used. It provides critical processing details such as temperatures, ratios, ranges, times, and rates. The article explains how to prepare aluminum components for electroplating, discussing surface roughening, anodizing, and immersion procedures along with expected results.

This article focuses on the types, composition, and applications of phosphate coatings and describes the characteristics of phosphate-coated ferrous and nonferrous materials, including steel and aluminum. It addresses five successive process fundamentals: cleaning, rinsing, phosphating, rinsing after phosphating, and chromic acid rinsing. The article describes the techniques for controlling the chemical composition of various phosphating solutions. It discusses the equipment and factors that influence equipment requirements in immersion and spray systems. The article also describes the controlling procedures of coating weight and crystal size. It provides guidelines for choosing phosphate coatings based on application, coating weight requirements, and recommended process parameters. The article concludes with a discussion on safety precautions and the treatment of effluents from phosphating plants.

Surface treatments are applied to magnesium parts primarily to improve their appearance and corrosion resistance. Mechanical and chemical cleaning methods are used singly or in combination, depending on the specific application and product involved to ensure repetitive reliability. This article focuses on mechanical finishing methods, namely, barrel tumbling, polishing, buffing, vibratory finishing, fiber brushing, and shot blasting. It provides useful information on process control and difficulties with chemical and anodic treatments of magnesium alloys. The use and applications of plating and organic finishing of magnesium alloys are also reviewed. The article concludes with a description of health and safety precautions to be followed during the surface treatment process.

Soluble salts on a surface can affect a steel substrate or coating in two principal ways: corrosion acceleration and osmotic blistering. This article provides a detailed discussion on the mechanisms for each of these deleterious effects. It describes the most detrimental anions with regard to corrosion, namely, chlorides, sulfates, and nitrates, and provides information on recognition and testing of the presence of soluble salts. The salt-measurement techniques and commercially available equipment are also described. The article provides information on research regarding tolerable levels of salts beneath coatings. The information shows that there appears to be a threshold limit to the salt contamination that a given coating/coating system can tolerate in a given environment.

Aluminum or aluminum alloy products have various types of finishes applied to their surfaces to enhance appearance or improve functional properties. This article discusses the procedures, considerations, and applications of various methods employed in the cleaning, finishing, and coating of aluminum. These include abrasive blast cleaning, barrel finishing, polishing, buffing, satin finishing, chemical cleaning, chemical brightening, electrolytic brightening, chemical etching, alkaline etching, acid etching, chemical conversion coating, electroplating, immersion plating, electroless plating, porcelain enameling, and shot peening.

Surface coatings are essential in all facilities that process nuclear materials or use nuclear fission for power generation. This article describes the coatings used in two basic types of Generation 3 nuclear reactor designs in the United States and their containment size. These reactors are the boiling water reactor (BWR) and pressurized water reactor (PWR). The article provides information on the loss-of-coolant accident (LOCA) identified as the design basis accident (DBA), which can rapidly de-water the core of an operating nuclear reactor. To avoid LOCA, both the BWR and the PWR include emergency core cooling systems. The article describes a DBA test and other coating performance parameters necessary for safety-related coating systems. It provides a detailed account of the selection criteria of coating types in a nuclear plant. The article concludes by highlighting protective coating strategies in Generation 3 Plants.

The sealing of the anodized aluminum is a critical process in achieving the durability and extended functionality of anodizing. This article discusses the different methods for sealing the anodic coatings produced by using sulfuric acid, namely, hot deionized water, hot nickel acetate, midtemperature, cold, and dichromate sealing. It reviews the factors that affect seal quality: immersion time, chemistry concentration, temperature, pH, water quality, coating thickness, and contaminants/dye bleeding. The article describes the various tests that are used for determining the quality of the seal, namely, salt spray, modified dye stain, acid dissolution, impedance, copper accelerated acetic acid salt spray, high-alkaline resistance, SO 2 fog, and clorox tests.

This article provides a discussion on the two basic steps of the batch hot dip galvanizing process: surface preparation and galvanizing. It describes the factors affecting coating thickness and coating structure. The mechanical properties of the coating and steel substrate are also discussed. The article also provides information on the various factors that should be considered before galvanizing a material. It examines the performances of galvanized coatings in corrosion service. The joining of galvanized structural members by bolting and welding is also discussed. The article describes the synergistic effects of galvanized and painted systems. It explains the applications of hot dip galvanized steel. The article concludes with information on pertinent galvanizing specifications under the authority of the American Society for Testing and Materials.

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.

Independent verification of coating system performance can be based on laboratory testing and/or field exposure. Qualification testing is a critical component to coating system selection. This article focuses on performance evaluations that are used to prequalify coating systems, namely, facility-specific, industry-specific, coating-type-specific, or a combination of these. It describes the standard laboratory tests used to generate performance data, namely, physical, compositional, chemical exposure, and application characteristics tests. The pros and cons of using manufacturer-generated data versus independently generated data are discussed. The article provides information on accelerated corrosion/weathering testing and nuclear level 1/level 2 service coatings qualification. It also describes the procedures for establishing minimum performance requirements and for determining when requalification testing may be required.