Metal in Construction

Been to cover iron structures with a protective coating. The term coating maybe taken as a reference to paint, but it is really much broader than that. Whatis reinforced concrete, for example, but steel with a very thick and brittlecoating Because concrete is brittle, it tends to crack and expose the steelreinforcing bars to corrosion. One of the functions served by prestressing orposttensioning is to apply a compressive force to the concrete in order to keepthese cracks from opening.

While one approach has been to apply coatings to prevent metal fromrusting, another has been to develop metals that inherently don’t rust. Rustmay be roughly dened as that dull reddish-brown stuff that shiny steel becomesas it oxidizes. Thus, the designation of ‘‘stainless” to those iron-basedmetals that have sufcient chromium content to prohibit rusting of the basemetal in atmospheric service. The ‘‘stain” that is presented is the rust stain.Stainless steel must have been a term that originated in someone’s marketingdepartment. The term confers a quality of having all the positive attributes ofsteel but none of the drawbacks.

If we were to apply a similar marketing strategy to aluminum, we mightcall it ‘‘light stainless steel.” After all, it prevents the rust stain as surely asstainless steel does, and it weighs only about one-third as much. Engineerswho regard aluminum as an alien material may be more favorably disposedtoward ‘‘light stainless steel.”For the past century and a half, then, structural engineers have relied onmetals to impart tension-carrying capability to structural components. Technicaldevelopment during that time has included improvement in the propertiesof the metals available for construction. One of the tasks of designersis to determine which metal best suits a given application.

While one approach has been to apply coatings to prevent metal fromrusting, another has been to develop metals that inherently don’t rust. Rustmay be roughly dened as that dull reddish-brown stuff that shiny steel becomesas it oxidizes. Thus, the designation of ‘‘stainless” to those iron-basedmetals that have sufcient chromium content to prohibit rusting of the basemetal in atmospheric service. The ‘‘stain” that is presented is the rust stain.Stainless steel must have been a term that originated in someone’s marketingdepartment. The term confers a quality of having all the positive attributes ofsteel but none of the drawbacks.

If we were to apply a similar marketing strategy to aluminum, we mightcall it ‘‘light stainless steel.” After all, it prevents the rust stain as surely asstainless steel does, and it weighs only about one-third as much. Engineerswho regard aluminum as an alien material may be more favorably disposedtoward ‘‘light stainless steel.”For the past century and a half, then, structural engineers have relied onmetals to impart tension-carrying capability to structural components. Technicaldevelopment during that time has included improvement in the propertiesof the metals available for construction. One of the tasks of designersis to determine which metal best suits a given application.