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What occurs during bimetallic/galvanic corrosion?
Which is an example of a problematic occurrence of bimetallic corrosion?
Which method is NOT recommended to prevent bimetallic/galvanic corrosion?
What is a significant disadvantage of stainless steel?
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Which of the following stainless steel grades is the most resistant to corrosion?
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What is an advantage of Brownbuilt sheeting over corrugated sheeting?
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Which of the following roof types allows for the smallest pitch?
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What is a disadvantage of weathering steel in buildings?
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What is a major disadvantage of the galvanizing process?
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Which surfaces should be avoided when using weathering steel?
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Which material is known to block UV rays effectively compared to glass?
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What is one of the properties of polycarbonate sheeting as compared to glass?
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What is a critical consideration for the long life of weathering steel?
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Which metal roofing types use concealed fixing?
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What thickness is specified for the hot-dipped galvanizing of corrugated mild steel roofing?
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What is a common aesthetic critique of galvanized materials?
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What is the minimum recommended roof slope for the Klip-Lok roofing profile type?
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For corrugated sheeting, what is the minimum recommended roof slope when overlapped?
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What is the approximate maximum purlin spacing for roof type (i)?
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What advantage does concealed fixing provide for roofing systems?
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Which of the following is a disadvantage of using weathering steel in aggressive environments?
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What is a Space frame in roofing structures?
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Which of the following is NOT an advantage of a Space frame roofing structure?
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What is a key characteristic of ferrous metals?
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Which of the following metals is classified as non-ferrous?
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What is Cor-Ten steel primarily known for?
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What happens to the rust layer formed on weathering steel over time?
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Which of the following is NOT a characteristic of non-ferrous metals?
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How do alloying elements in weathering steel contribute to its corrosion resistance?
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Which type of stainless steel is recommended for outside balustrades at a beachfront restaurant?
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What is the most corrosion-resistant stainless steel grade used in the building industry?
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What is a benefit of frequent cleaning of stainless steel?
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When installing a curtain wall system, what is the first step in the process?
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Which type of finish is recommended to prevent early discoloration of stainless steel cladding?
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Why are marks and scratches on stainless steel not typically removed with steel wool?
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What is a defining characteristic of a curtain wall system?
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Which application would be best served by using Type - 304 stainless steel?
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Study Notes
Weathering Steel
- Weathering steel can stain and looks dirty.
- Corrosion products should be diverted from vulnerable surfaces.
- South facades are not suitable for using weathering steel.
- Avoid using weathering steel in contact with absorbent surfaces like concrete.
- Avoid using weathering steel in prolonged wet conditions.
- Avoid burying weathering steel in soil.
- Avoid using weathering steel in contact with dissimilar metals like galvanized or electroplated nuts and bolts.
- Avoid using weathering steel in aggressive or marine environments.
- Avoid using weathering steel on south facades.
Using Weathering Steel
- Consider corrosion allowance for long life.
- Avoid crevices and water/dirt traps.
- Rust staining may occur on adjacent surfaces.
- Surface blasting may be necessary for even weathering results.
- Use fasteners made of weathering steel.
- Drainage should be carefully planned to avoid staining.
Metal Roofing Types
- Klip-Lok, IBR Sheeting, Corrugated Sheeting, and Brownbuilt roofing are popular metal roofing types.
- Brownbuilt and Klip-Lok use a concealed fixing method, which secures the sheeting to a specialized bracket that is not exposed to the outside environment.
- Concealed fixing provides superior watertightness compared to traditional screw-fix roofs.
- The minimum recommended roof slope for Klip-Lok is 3º, but notes recommend 1º.
- When over lapped, the minimum recommended roof slope for corrugated sheeting is 15º. When not overlapped, the minimum recommended roof slope is 7º.
- Brownbuilt sheeting has a smaller pitch than corrugated sheeting.
- Brownbuilt sheeting is not penetrated in the fixing process, creating less chance of leaks, unlike corrugated sheeting.
- Brownbuilt sheeting can be shaped and curved, unlike corrugated sheeting.
Polycarbonate vs. Glass
- Polycarbonate is lighter and more robust than glass.
- Polycarbonate also blocks UV rays, offering a significant advantage over glass.
Galvanizing Advantages
- Galvanizing is durable and long-lasting.
- Galvanizing is tough.
- Galvanizing provides a rust-free finish.
- Galvanizing requires less maintenance.
- Galvanizing offers a clean finish, ideal for clinical environments.
Galvanizing Disadvantages
- Galvanizing is more expensive than steel prices, especially for large-scale projects.
- Galvanizing is not very aesthetically pleasing.
- Zinc hydroxide (white rust) can form if exposed to moisture, requiring immediate treatment to prevent compromising durability.
- Galvanizing cannot be applied on-site.
- The dimensions of parts are limited by the size of the zinc bath.
Space Frame
- A space frame is a fully three-dimensional two-way spanning space framework (square on square).
- It is a rigid, lightweight, truss-like structure constructed from interlocking struts in a geometric pattern.
Space Frame Advantages & Disadvantages
-
Advantages:
- Even load distribution.
- Reduced deflections.
- Easy installation of services.
- Simplified fixing details.
- Factory made.
- Modular.
- Assembled at ground level.
-
Disadvantages:
- Expensive
- Fixed geometry
- Can appear complicated and complex.
Ferrous Metals
- Ferrous metals contain iron.
- Ferrous metals include mild steel, carbon steel, stainless steel, cast iron, and wrought iron.
- They are primarily used for tensile strength and durability, especially mild steel in building construction.
Non-Ferrous Metals
- Non-ferrous metals do not contain iron.
- Non-ferrous metals include aluminum, brass, copper, nickel, titanium, lead, and zinc, as well as precious metals like gold and silver.
- While they can provide strength, their differences from ferrous metals are advantageous.
- High corrosion resistance.
- Good thermal and electrical conductivity.
- Non-magnetic
Weathering Steel
- Cor-Ten steel is a popular weathering steel.
- Weathering steel's corrosion resistance comes from alloying elements that react with the environment to form an adherent and less porous rust layer.
- This protective layer reduces the corrosion rate over time.
Bimetallic/Galvanic Corrosion Explained
- Bimetallic/galvanic corrosion is an electrochemical process where one metal (anodic metal or sacrificial metal) corrodes preferentially when in electrical contact with a dissimilar metal in the presence of an electrolyte.
Bimetallic/Galvanic Corrosion Example
- Corrosion between steel and brass can occur.
- When the protective paint layer peels or cracks, steel is exposed to oxygen and water, initiating corrosion.
Preventing Bimetallic Corrosion
- Avoid cavities.
- Use bolted joints instead of welded joints.
- Avoid or seal lap joints.
- Provide drainage holes for water.
- Provide free air circulation around the structure.
Stainless Steel
- Stainless steel provides long-term value, low maintenance costs, versatile uses, and aesthetic value.
- However, stainless steel can be very expensive, difficult to clean, and susceptible to scratches and dents.
Stainless Steel Grades
- The most corrosion-resistant stainless steel grade used in the building industry is Type 2205 (Duplex).
- Stainless steel grades from most to least corrosion resistance:
- Type 316
- Type 2205
- Type 304
- Type 430
Stainless Steel Applications
- Outside balustrade at office building in Newton Park: Type 316
- Internal stair balustrade: Type 304.
- Outside balustrade for restaurant at the beachfront: Type 316.
- Outside balustrade at office building in Summerstrand: Type 316.
- Outside balustrade for a double-storey house in Bloemfontein: Type 304.
Stainless Steel Corrosion Resistance
- Lower alloy grades of stainless steel resist corrosion in normal atmospheric and potable water environments.
- Higher alloyed grades can resist corrosion in many acids and alkaline solutions, and some chloride-bearing environments, making them suitable for process plants.
Stainless Steel Maintenance
- Frequent cleaning of stainless steel by heavy rain or manual washing does prevent corrosion. (True)
Stainless Steel Grain Orientation
- Using a vertical surface finish grain orientation on stainless steel cladding does prevent early discoloration/corrosion. (True)
Stainless Steel Scratches
- Marks and scratches on stainless steel can be removed using steel wool. (True)
Galvanized Fasteners
- Galvanized fasteners should not be used to fasten stainless steel panels. (False)
Stainless Steel Dirt Accumulation
- Accumulation of dirt can lead to premature corrosion of stainless steel panels. (True)
Curtain Wall Systems
- A curtain wall system is an outer covering of a building where the outer walls are non-structural, merely keeping the weather out and occupants in.
- Stick system and Unitized system are two popular curtain wall systems.
Stick System Installation
- The stick system installation involves fixing anchors to the building floors, then securing design panels onto them.
Cellular Beam
- The beam in the illustration is a cellular beam.
- The holes in the beam are characteristic of a cellular beam.
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Description
This quiz covers essential knowledge about weathering steel, including its properties, usage recommendations, and potential issues such as corrosion and staining. Additionally, it provides insights into different types of metal roofing, focusing on their suitability and maintenance. Test your understanding of these topics to enhance your building material expertise.
