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82 Corrosion Control Through Organic Coatings 4.6.2 WHAT FORMS OF SILICA CAUSE SILICOSIS? Not all forms of silica cause silicosis. Silicates are not implicated in the disease, and neither is the element silicon (Si), commonly distributed in the earth’s crust and made famous by the semiconductor industry. Silicates (-SiO 4) are a combination of silicon, oxygen, and a metal such as aluminum, magnesium, or lead. Examples are mica, talc, Portland cement, asbestos, and fiberglass. Silica is silicon and oxygen (SiO 2). It is a chemically inert solid that can be either amorphous or crystalline. Crystalline silica, also called “free silica,” is the form that causes silicosis. Free silica has several crystalline structures, the most common of which (for industrial purposes) are quartz, tridymite, and cristobalite. Crystalline silica is found in many minerals, such as granite and feldspar, and is a principal component of quartz sand. Although it is chemically inert, it can be a hazardous material and should always be treated with respect. 4.6.3 WHAT IS A LOW-FREE-SILICA ABRASIVE? A low-free-silica abrasive is one that contains less than 1% free (crystalline) silica. The following are examples of low-free-silica abrasives used in heavy industry: • Steel or chilled iron, in grit or shot form • Copper slag • Boiler slag (aluminium silicate) • Nickel slag • Garnet • Silicon carbide (carborundum) • Aluminium oxide 4.6.4 WHAT HYGIENIC MEASURES CAN BE TAKEN TO PREVENT SILICOSIS? The best way to prevent silicosis among abrasive blasters is to use a low-free-silica abrasive. Good alternatives to quartz sand are available (see Section 4.2). In many countries where dry blasting with quartz sand is forbidden, these alternatives have proven themselves reliable and economical for many decades. It is possible to reduce the risks associated with dry abrasive blasting with silica. Efforts needed to do so can be divided into four groups: • Less-toxic abrasive blasting materials • Engineering controls (such as ventilation) and work practices • Proper and adequate respiratory protection for workers • Medical surveillance programs The National Institute for Occupational Safety and Health (NIOSH) recommends the following measures to reduce crystalline silica exposures in the workplace and prevent silicosis [28]: • Prohibit silica sand (and other substances containing more than 1% crystalline silica) as an abrasive blasting material and substitute less hazardous materials. • Conduct air monitoring to measure worker exposures. © 2006 by Taylor & Francis Group, LLC
Blast Cleaning and Other Heavy Surface Pretreatments 83 • Use containment methods, such as blast-cleaning machines and cabinets, to control the hazard and protect adjacent workers from exposure. • Practice good personal hygiene to avoid unnecessary exposure to silica dust. • Wear washable or disposable protective clothes at the worksite; shower and change into clean clothes before leaving the worksite to prevent contamination of cars, homes, and other work areas. • Use respiratory protection when source controls cannot keep silica exposures below the NIOSH Recommended Exposure Limit. • Provide periodic medical examinations for all workers who may be exposed to crystalline silica. • Post signs to warn workers about the hazard and inform them about required protective equipment. • Provide workers with training that includes information about health effects, work practices, and protective equipment for crystalline silica. • Report all cases of silicosis to state health departments and to the Occupational Safety and Health Administration (OSHA) or the Mine Safety and Health Administration. For more information, the interested reader is encouraged to obtain the free document, Request for Assistance in Preventing Silicosis and Deaths from Sandblasting, DHHS (NIOSH) Publication No 92-102, which is available at www.osha.gov or by contacting NIOSH at the following address: REFERENCES Information Dissemination Section Division of Standards Development and Technology Transfer NIOSH 4676 Columbia Parkway Cincinnati, Ohio 45226 USA 1. Good Painting Practice, Vol. 1, Keane, J.D., Ed., Steel Structures Painting Council, Pittsburgh, PA, 1982. 2. Handbok i rostskyddsmålning av allmänna stålkonstruktioner. Bulletin Nr. 85, 2nd ed., Swedish Corrosion Institute, Stockholm, 1985. (In Swedish.) 3. Evaluation of copper slag blast media for railcar maintenance, NASA-CR-183744, N90-13681, National Aeronautics and Space Administration, George C. Marshall Space Flight Center, AL, 1989. 4. Bjorgum, A., Behandling av avfall fra bläserensing, del 3. Oppsummering av utredninger vedrorende behandling av avfall fra blåserensing. Report No. STF24 A95326, Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology, Trondheim, 1995. (In Norwegian.) 5. Eggen, T. and Steinsmo, U., Karakterisering av flater blast med ulike blåsemidler, Report No. STF24 A94628, Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology, Trondheim, 1994. (In Norwegian.) © 2006 by Taylor & Francis Group, LLC
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Corrosion of Ceramic and Composite
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Published in 2006 by CRC Press Tayl
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Preface This book has been written
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Author Amy Forsgren received her ch
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Contents Chapter 1 Introduction ...
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2.4.2 Reactive Reagents ...........
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6.2.4.1 Alkaline Blistering........
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1 Introduction This book is not abo
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Introduction 5 1.2.2 ELECTROLYTIC R
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