Structural steel is a common choice for many industries, including concrete, buildings, architecture, construction, and infrastructure. Corrosion can cause safety issues like instability and other hazards, making it a crucial concern. The annual global cost of corrosion is an astounding $2.5 Trillion, estimated at 3.4% of the world's gross domestic product. This is why implementing preventative steps is critical to avoiding corrosion failures.
The tragic collapse of the Champlain Tower Condominiums in Surfside, Miami, claiming the lives of 98 people, is a reminder of how important it is to address corrosion issues promptly and effectively. A significant factor in this catastrophic collapse was the prolonged deterioration of reinforced concrete structural support due to water infiltration and corrosion of the reinforced steel.
This article examines the eight key steps to avoiding corrosion failures and guaranteeing that structures are durable and safe.
What is Corrosion, and How Does it Affect Steel Structures?
Corrosion is a chemical process resulting from the infiltration of moisture and oxygen, which returns refined metals to their natural and stable ore state. Even though steel is a corrosion-resistant material, prolonged exposure to environmental conditions like seawater, hydrocarbons, or saltwater fog can result in corrosion.
This reaction weakens the steel structure, and the iron in the steel oxidizes, reducing steel material. A red rust is produced four to seven times the volume of steel. The increase in volume produces stress in the concrete, causing it to crack. This results in the delamination of parking garage slabs and concrete bridge decks and the loss of concrete cover on columns, beams, and girders. This shortens a steel structure’s lifespan.
Preventive maintenance routines like regular painting, rustproofing, and routine inspections for signs of corrosion will help reduce corrosion when implemented.
Types of Corrosion That can Occur on Steel Structures
Steel structures are popular in construction due to their durability, strength, and low cost. However, corrosion can adversely affect steel installations if appropriate measures are not taken.
Several types of corrosion damage affect steel structures, including general, uniform, galvanic, pitting, stress corrosion cracking, and crevice corrosion.
Each type of corrosion causes varying problems and requires different preventative measures for maximum effectiveness.
Understanding the various corrosion processes is vital in establishing good maintenance routines to protect your investment in structural steel.
Structural Effects of Corrosion
- Loss of Strength — The process of steel corroding causes the expansion of the corrosion products. The result is a compromised steel layer over the reinforcement's surface that has a reduced bond with the surrounding concrete. There is a reduction in the section's capacity.
- Fatigue — The fatigue strength can be reduced with the development of pitting corrosion. It creates additional points of stress concentration where cracking could develop.
- Reduced Steel-Concrete Bond — When steel corrodes, the corrosion products expand, leaving a compromised steel layer over the reinforcement's surface and a poor bond with the surrounding concrete.
- Limited Ductility — A lower ductility limits the plastic deformation of corroded sections. This affects the seismic reaction of the elements.
Key Steps to Prevent or Mitigate Corrosion Damage on Steel Structures
Although steel is considered a very durable metal, it is vulnerable to corrosive elements that can reduce its expected lifespan. Steel is commonly used to build structures, but preventative measures must be taken to mitigate its vulnerability to corrosion.
Several measures help prevent or mitigate corrosion damage to steel structures. Rust inhibitors, including coatings and sacrificial anodes, prevent oxygen and moisture from infiltrating the metal surface by creating a barrier.
Galvanizing is the application of a zinc coating to prevent oxidation and rusting of the metal. Surface treatments and proper maintenance can reduce the likelihood of corrosion occurring.
Regular inspections of steel structures can provide early warning signs of developing corrosion, allowing preventative steps to be taken quickly. Cleaning clogged gutters, repairing broken seals, and painting over peeled-off paint can prevent oxygen and water infiltration to the metal surface, potentially stopping corrosion damage.
Considering the following steps can help safeguard the durability of structural steel.
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Consider Steel Selection & Design
Begin by choosing the correct steel and quality materials. A higher grade of steel can help prevent corrosion. A low alloy steel or lower-quality steel can be vulnerable to weakness when rust occurs. Utilizing corrosion-resistant alloys like stainless steel, aluminum, or copper helps prevent corrosion.
In addition, choosing the right design and engineering to reduce risk factors is vital for structural steel installations. The design should minimize atmospheric exposure, prevent water from accumulating, and avoid irregular surfaces and the use of varying metals.
Options include choosing thicker sections of metal that provide more corrosion resistance, utilizing a coating system resistant to oxidation that can also reduce air infiltration to the metal surface, or preventing aggressive chemicals from contacting the steel. Implementing these steps helps protect the investment made in structural steel by ensuring a durable and safe structure for years.
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Consider the Impact of Location
The location chosen for a steel structure significantly impacts the risk of corrosion. Environmental factors like proximity to water, air pollution, industrial activities, and salt spray influence the rate of rust forms on steel.
Structures in coastal areas are more vulnerable to corrosion, such as rust, due to the high salt concentration in the air. This can apply to areas with high levels of environmental pollutants because toxins increase the corrosion rate.
Inspections should be completed regularly to discover possible sources of corrosion damage and rectify as required.
Protecting steel structures in high-risk areas like coastal regions is critical. For maximum protection, galvanizing and other coatings are recommended. It is also important to ensure that ventilation around the structure can adequately reduce humidity levels and impede corrosion processes.
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Test and Prepare Your Surface
A significant reason for corrosion is the failure to correctly test and prepare the surface. The steel surface should be tested for contamination prior to preparation. Steel structures require thorough cleaning and preparation before applying paint or any other coating.
To prevent issues with coating quality and adhesion, test for surface salts, surface roughness, and surface profile to establish the level of surface preparation required. The surface should be tested with a galvanometer to confirm an appropriate level of adhesion between the metal and paint.
Gardco can provide a wide range of surface profile testers, thickness gauges, conductivity meters, and refractometers.
Surface preparation methods can be simple chemical pre-cleaning to abrasion methods like grinding and abrasive blasting. Steel surface preparations are designed to remove physical defects and loose or soluble contamination before applying coatings.
Chemical stripping can be a cost-effective choice for cleaning a few square feet. Pickling or abrasive blasting is better when the prepared surface is several thousand square feet.
Apply the protective coating that will prolong the life and well-being of a steel structure after thoroughly cleaning and removing the rust.
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Apply Protective Coatings
Protective barrier coatings are the most effective way to prevent corrosion on structural steel. Applying protective coatings significantly extends the life of a steel structure. There are many distinct types of coatings, including zinc-rich primer, epoxy coating, and acrylic-based paints.
The coatings form a protective barrier between the metal surface, oxygen, and moisture, helping to prevent corrosion. It is essential to ensure that coatings are correctly applied and checked regularly to maintain good condition. The industry considers applying multiple layers of rust-inhibiting primer a critical step in protecting structural steel.
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Install Quality Insulation and Ventilation
Excess moisture escaping from the insulation and mixing with oxygen speeds up corrosion. Installing quality insulation and ventilation prevents excess moisture, and less moisture means fewer issues.
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Choose a Highly Qualified, Professional Building Company
When choosing a building partner for your construction project, selecting a company with experience and knowledge in steel fabrication and corrosion prevention is essential.
A quality building company will understand the science behind corrosion and advise on the choice of materials, the best location, and the right design to prevent corrosion. This helps reduce the risk of corrosion and assures that the steel structure has been built to last many years.
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Ongoing Protective Coatings Testing
Regularly testing protective coatings helps identify the areas that require repair. To ensure that a steel structure remains free of corrosion, routine testing of the coating thickness, adhesion to the metal surface, and visual inspection of any defects is vital.
In addition, monitoring environmental conditions, such as humidity, temperature, and air pollution, can prevent structural steel from developing long-term corrosion damage.
Case Studies of Corrosion Concerns with Steel Structures
Steel is essential in many building projects; however, when exposed to environmental conditions like sea air and wet climates, it can experience accelerated corrosion. The structural integrity is threatened, and it is vital for engineers and architects to diligently implement preventative steps to protect steel structures.
Many successful case studies document how diligent anti-corrosive strategies can prevent the effects of corrosion on steel structures. For example, a study demonstrated that prefabricated stainless steel coating systems utilized in a highly polluted industrial environment substantially reduced maintenance costs and increased the service life of a structure by at least five times.
Other examples have highlighted the effectiveness of linseed oil applied on visually corroded items or kinetic protection methods like thermal spray aluminum coatings. Case studies of successful corrosion treatment on steel structures inform professionals of the best practices for protecting against corrosion with longer-lasting results.
In a study published on IOPScience, researchers examined two major types of corrosion damage in steel. Fatigue and stress corrosion cracking create significant issues in steel structures.
Test specimens were prepared by researchers who utilized special devices and loading frames to complete their experiments. They discovered that three different chemical solutions substantially impacted the fatigue life of specimens from an L485MB steel crude oil pipeline IKL.
In the second part of the study, the focus was on the negative effects of stress corrosion cracking on structural steel CSN411353. It was discovered that stress corrosion cracking significantly reduced the steel's fracture toughness.
Another study recently published by ScienceDirect reviewed this issue in depth. The focus was on steel frame structures and how they perform with a continuous attack of corrosion. Researchers considered an anomaly referred to as lateral torsional buckling, which occurs when something is twisted and bent until it buckles under pressure.
The study discovered that when corrosion and lateral torsional buckling were both considered, there was a substantial decrease in the load-carrying capacity of the structures.
The study emphasizes the need to consider corrosion in structural analysis and design. It is a wake-up call for engineers and architects to design steel structures capable of withstanding a corrosive onslaught and perform at required levels throughout their service life.
An article from AMPP titled ‘Protecting Steel-Reinforced Concrete Marine Structures from Corrosion’ discusses how corrosion of reinforced steel is the primary reason for the deterioration of steel-reinforced concrete structures.
A recent study on MDPI tackled this issue by investigating existing corrosion models. They evaluated their effectiveness under various corrosivity classes using the ISO standard. These models help predict the amount of damage corrosion can cause over time.
The researchers also took an intensive look into a real-world case study with the finite element method (FEM), examining how corrosion affects the structure's dynamic characteristics over its lifetime.
The findings revealed that corrosion affected the dynamic characteristics of the structure substantially. For example, the vibration period expanded by up to 15% for high-corrosivity class structures with a lifespan of 100 years. The corroded structure had a higher acceleration and drift demand, with the base reaction forces reduced by up to 60% for the same class and period.
Proactive measures, including stainless steel coatings, linseed oil applications, kinetic protection techniques, and the innovative use of corrosion models, can turn the tide against corrosion. Each case study gives engineers and architects a best practice guide for long-lasting, corrosion-resistant structures.
The Future of Preventing Corrosion on Steel Structures
Avoiding moisture condensation on surfaces using advanced coatings is the most efficient method to prevent corrosion on steel structures. Polyurethane-based products, epoxy additive polysiloxane polymer, or water-based acrylic formulations are developed to vigorously protect against corrosive environments.
These coatings offer superior performance for use in coastal, industrial, and environments with exposure to saltwater, chemical pollutants, and humidity. In addition, the coatings should be tested and checked regularly for reoccurring wear and tear. An approach that combines galvanizing, painting, and routine monitoring for signs of corrosion should allow steel structures to achieve expected lifecycles even in the harshest environments.
Corrosion is one of the most significant issues in the industrial sector. It affects steel and concrete surfaces by exploiting acids, alkalis, chemicals, and solvents. Implementing the above measures can significantly decrease the risks of structural steel corrosion, guaranteeing a lasting and safe installation.
Protecting metal structures from the beginning is critical. However, inspecting and maintaining steel installations on a regular basis reduces the risk of corrosion damage. Understanding the reasons and degree of deterioration assists in developing strategies for repairing and protecting structures. Strategies that extend the life and preserve steel structures subjected to harsh environmental conditions for years are vital.
A comprehensive corrosion prevention system’s entire design should provide many years of protection to the substrate. A balanced system considers the environment, design, and coating systems to achieve the required performance and service life cycle for the lowest cost. Implementing these steps will result in a lasting structure with minimal disruption. Protecting structural steel is essential in maintaining any asset's integrity.
This information has been sourced, reviewed and adapted from materials provided by Paul N. Gardner Company, Inc.
For more information on this source, please visit Paul N. Gardner Company, Inc.