Corrosión y Degradación de Materiales

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Questions and Answers

¿Qué tipo de corrosión se relaciona con la formación de burbujas de vapor en un líquido?

Corrosión por contacto

Corrosión por cavitación (correct)

Corrosión microbiológica

Corrosión atmosférica

¿Cuál de las siguientes afirmaciones sobre la corrosión de los materiales es incorrecta?

Todos los materiales pueden corroerse.

La corrosión solo es visible en el exterior de los materiales. (correct)

La corrosión se acelera en contacto con fluidos.

Los metales muestran diferentes colores de corrosión según el líquido.

¿Qué factores tienen un impacto directo en la velocidad de corrosión de un material?

Tipo de material y color

Temperatura y humedad (correct)

Tamaño y forma

Rigidez y brillo

¿Qué tipo de corrosión se produce por la descomposición fotocanítica de los plásticos?

Corrosión fotográfica Signup and view all the answers

¿Cuál de las siguientes es una característica de la corrosión metálica?

Dependencia del tipo de líquido en contacto. Signup and view all the answers

¿Cuál de las siguientes afirmaciones sobre la reacción del CO2 con el concreto es correcta?

Corroe el concreto y altera sus propiedades. Signup and view all the answers

¿Cuál de los siguientes métodos es un ejemplo de protección catódica en materiales?

Utilizar un ánodo de sacrificio como Mg o Zn. Signup and view all the answers

¿Qué caracteriza a la etringita en el concreto?

Son cristales con forma de aguja que aumentan el volumen del concreto. Signup and view all the answers

En el contexto de la degradación de polímeros, ¿cuál de las siguientes condiciones no contribuye a su degradación?

El almacenamiento en un ambiente controlado y seco. Signup and view all the answers

¿Qué describe mejor el proceso de polimerización?

La unión de monómeros para formar polímeros. Signup and view all the answers

¿Cuál es el comportamiento de un polímero a temperaturas por debajo de la temperatura de transición vítrea (Tg)?

Se vuelve más quebradizo. Signup and view all the answers

¿Qué característica no es típica de los cerámicos tradicionales?

Alta conductividad eléctrica. Signup and view all the answers

¿Cuál de las siguientes afirmaciones sobre la estructura cerámica es incorrecta?

Pueden ser totalmente amorfas en su estructura. Signup and view all the answers

¿Cuál de las siguientes afirmaciones se aplica correctamente a las cerámicas nuevas?

Tienen propiedades mecánicas excelentes y altos puntos de fusión. Signup and view all the answers

¿Qué subunidad básica es característica de las cerámicas amorfas (vidrio)?

SiO4. Signup and view all the answers

¿Cuál de las siguientes afirmaciones es verdadera sobre las propiedades térmicas de los polímeros?

Los polímeros amorfos presentan una orientación de cadena desordenada. Signup and view all the answers

¿Cómo influye el grado de cristalinidad en las propiedades de un polímero?

Un polímero transparente en estado amorfo es opaco en estado semicristalino. Signup and view all the answers

¿Cuál es la característica principal de los copolímeros en comparación con los homopolímeros?

Los copolímeros se componen de dos o más diferentes monómeros. Signup and view all the answers

¿Qué tipo de polímero se caracteriza por tener cadenas de alta flexibilidad con un cierto grado de entrecruzamiento?

Elastómeros. Signup and view all the answers

¿Cuál de las siguientes propiedades de un polímero aumenta con una alta densidad de polietileno (PE)?

El punto de fusión aumenta. Signup and view all the answers

Study Notes

Corrosion - Treatments

Materials degrade due to use, application, and corrosion (or a combination of both).
Corrosion is the interaction of metals with their surroundings, leading to chemical changes and property deterioration.
Iron + Oxygen = Iron Oxide (FeO₂). Atmospheric and technological advancements make corrosion more severe and result in significant losses.
Corrosion speeds up with fluids, leading to pipe failures.
Corrosion-Cavitation: Vapor bubbles in a liquid, due to pressure changes, form and collapse near metal surfaces, causing physical and chemical damage to the material.
Corrosion can occur internally, making it invisible on the surface (e.g., pipes, cables).
Different metals corrode in various ways. Corrosion susceptibility depends on the material.

Corrosion Examples

Metals: Discoloration varies depending on the liquid (e.g., yellow (silver), green (copper/bronze)). Air: discoloration (yellow - silver, green - copper/bronze), water: discoloration (gray/green - copper, gray/various hues - lead), and black (lead).
Ceramics: discoloration, erosion, and the presence of organisms (bacteria, molds).
Atmosphere: (humidity): discoloration and weakening (cement), discoloration (sandstone).
Water: Erosion (limestone), moss, lichen, and bacteria (granite).
Plastics: Decolorization/swelling may take time, but is affected by temperature cycles, sunlight exposure, and liquid exposure.

Why Materials Corrode

Naturally occurring materials are often already mixed with other substances. Obtaining pure materials requires energy. Corrosion returns the material to its natural state, releasing energy.
Processes involved in treating and shaping materials can be disrupted by corrosion, which makes the materials more susceptible to further degradation.

Material Construction Examples

Chlorides: CO₂ + Oxygen in reinforced concrete. Chlorides dissolve in water and permeate concrete pores. CO₂ reacts with concrete compounds (Ca(OH)₂) forming CaCO₃, which lowers pH and damages the properties of the cement.
Sulfates: (SO₄²⁻) in concrete. Substitution of Mg²⁺/Ca²⁺ leads to MgSO₄ and Ca(OH)₂ formation, generating Mg(OH)₂ crystals, causing concrete cracking due to volume increase.
Metal Corrosion: Caused by atmosphere, rain, and other conditions, varying in severity among different metals.
Polymer Degradation: Caused by heat, radiation, and water.

Corrosion Protection

Material Selection: Choosing the right material for the intended application (e.g., titanium instead of iron for a structure).
Design: Preventing galvanic cells (contact of dissimilar metals), and proper material joining techniques are vital (e.g., welding, adhesives are more corrosion-resistant than riveting).

Methods of Protection

Coatings: (Permanent) act as barriers against corrosion (e.g., paints, plating with nickel).
Cathodic Protection: Using a more reactive metal to protect the material. The reactive metal gets consumed to protect the material of interest (e.g., zinc coating protects steel).
Inhibitors: Substances added to the environment in small quantities to slow down the corrosion process by creating protective layers on the material’s surface.

Polymers

Organic substances of natural or synthetic origin with high molecular weights. Polymers are formed through the linking of smaller molecules called monomers.
Polymerization: The process of creating a polymer from monomers.
Degree of Polymerization: The number of repeating units in a polymer chain.

Polymer Properties

Physical Properties: Often have low melting temperatures, are thermal and electrical insulators, and have high coefficients of expansion.
Mechanical Properties: Typically display lower strength and ductility compared to metals.
Chemical Properties: Generally stable in aggressive environments.

Polymer Structures

Linear: Consist of a single chain with repeating monomers. (Thermoplastics)
Branched: Possess side chains attached to the main chain. (Thermoplastics)
Cross-linked: Monomers are linked together to form a network. (Thermosets)
Network: A network of cross-linked polymer chains. (Thermosets)

Ceramic Properties

Physical Properties: High melting points, excellent thermal and electrical insulation, but brittle and hard.
Chemical Properties: Resistant to chemical attack, but can be sensitive to thermal shock (rapid temperature changes).

Ceramic Structures

Ceramics are compounds composed of metallic and nonmetallic elements. They are typically ionic or covalent.
They form stable lattices when cations and anions are appropriately positioned

Traditional Ceramics

Silicates, silica, and alumina are often used in ceramics.
Silicon dioxide (silica) is the primary constituent in many types of rock in the earth's crust.
Alumina (aluminum oxide): commonly used in refractories (heat-resistant materials) and other high-temperature applications.
New Ceramics (e.g. aluminum oxide, silicon carbide): designed for specific applications due to their high mechanical strength and high melting point.

Glass/Glass Products

Often made up of silica (SiO2), soda (Na₂O) and lime (CaO), and other additives.
Properties depend on the chemical composition.

Concrete

Mixture of aggregates, cement, and water.
Cement reacts with water to form a solid material binding the aggregates (stone, sand, gravel) together.

Polymer Concrete

Concrete reinforced with polymers.
Polymer concrete enhances the material's properties such as flexibility, resistance to aggressive environments, and other similar traits

Metals and Alloys

Metallic Bonding:
Electrical Conductivity:
Heat Conductivity:
Plasticity: The ability to be deformed permanently without fracture.
Alloying: The process of combining different metals or a metal with a nonmetal substance to produce an alloy.

Ferrous Alloys (e.g., Steel)

Primarily iron, but containing carbon.
Steel - Iron with carbon, used for various structural applications.
Other alloys (e.g., cast iron).

Non-ferrous Alloys (e.g., Aluminum)

Aluminum - Good strength, lightweight and conductive.
Other alloys (e.g., copper alloys, like bronze and brass).

Steel Treatment Techniques

Annealing: Heat treatment to soften steel.
Normalizing: Heat treatment to improve uniformity of microstructure.
Hardening: Heat treatment to increase hardness.
Tempering: Heat treatment to reduce brittleness after hardening.
Case Hardening (Surface Hardening): Enhancing only the surface area of a component, making it stronger and resistant to wear. For example, nitriding, carburizing (increasing the carbon content).

High-Alloy Steels (e.g., Stainless Steel)

High Cr content for superior corrosion resistance.
Alloying elements (e.g., nickel and molybdenum).

Non-ferrous Alloy Examples

Alloys of copper (e.g., brass, bronze, nickel, etc.)
Alloys of aluminum.
Titanium alloys.

Heat Treatment Testing

Jominy Test: Used to assess the hardenability of steel specimens. A specimen is heated and quenched at one end, and the hardness is measured at different locations along the length of the component.

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Description

Este cuestionario aborda diversos tipos de corrosión y su relación con diferentes materiales, así como la degradación de polímeros y cerámicos. A través de preguntas específicas, se evaluará tu conocimiento sobre los procesos de corrosión, polimerización y las condiciones que afectan la durabilidad de estos materiales. ¡Pon a prueba tus conocimientos y aprende más sobre la ciencia de los materiales!