Answers

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  What should I do if rust is found on the goods upon arrival at port?

  Upon discovering rust, immediately notify the carrier/shipping company, insurance company, freight forwarder, and supplier in writing (email is best).
  Take comprehensive photos and videos of the rusted goods, including: the original condition of the container/ship hold when opened, close-ups of the rusted areas, cargo labels/marks, packaging condition, etc. Determine liability at which stage the rust occurred.
  Based on the liability determination, decide whether to file a claim with the supplier, shipping company, or the insurance company.
  
  The situation can be avoided later
  Before loading the goods, commission a third-party inspection agency to inspect and record the surface condition of the steel.
  If any defects are found in the goods before loading, require the carrier to make accurate annotations on the mate's receipt and bill of lading.
  Clearly stipulate in the purchase contract: rust acceptance standards (such as allowable rust level and area ratio), quality objection period, claim process, etc.

  
  
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  What are the special requirements for steel structure corrosion protection in coastal environments?

  Coastal areas have high humidity and salt content, making steel space frames prone to corrosion, which affects the structure's service life and safety.
  Selecting Corrosion-Resistant Materials: In coastal areas, it is recommended to use steel with excellent corrosion resistance. Weathering steel exhibits good corrosion resistance in atmospheric environments.
  Anti-Corrosion Coating: Use a high-performance anti-corrosion coating, such as a three-layer anti-corrosion system of epoxy zinc-rich primer + epoxy micaceous iron oxide intermediate paint + polyurethane topcoat. The coating thickness should be selected according to environmental conditions; generally, a total thickness ≥200 µm is recommended.
  Catholic Protection: Install a cathodic protection system in the space frame structure, such as a sacrificial anode or impressed current cathodic protection system, to further improve the structure's corrosion resistance.

  
  

  In coastal environments, steel structures corrode extremely rapidly, thus requiring very specific corrosion protection measures. This is mainly reflected in the need for more stringent corrosion protection design levels, thicker coating systems, and more stringent construction and acceptance standards.
  
  Environmental Classification: Accurately determine the C5 or CX level according to ISO 12944.
  System Selection: Select a heavy-duty anti-corrosion coating system with a total dry film thickness of at least 280μm.
  Reinforcement of Critical Components: For ultra-long service life or underwater structures, employ composite measures such as thermal spraying of metal or cathodic protection.
  Strict Construction and Acceptance Control: Strictly adhere to Sa 2.5 grade surface treatment and coating quality testing.
  
  The final solution must be determined comprehensively based on factors such as the specific structural type, design life, and construction conditions.

  
  
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  Differences between High-Frequency Welded H-Beams and Hot-Rolled H-Beams

  Hot-Rolled H-Beams: Formed in one pass by heating continuously cast billets or ingots in a four-roll universal mill. The process is complex, requiring high-end equipment, and is typically produced by large steel mills. Hot-rolled H-beams have a scientifically sound structure, good plasticity and flexibility, and high structural stability, making them suitable for building structures subjected to high vibration and impact loads. They also have strong resistance to natural disasters. They are easy to manufacture mechanically, allowing for intensive production, high precision, convenient installation, and easy quality assurance. They can be used to build actual house construction factories, bridge construction factories, and industrial plant construction factories. The development of steel structures has created and driven the development of hundreds of emerging industries.
  
  High-Frequency Welded H-Beams: Cut strip steel (or plate) of suitable thickness to a suitable width, and weld the edges (flanges) and web directly on a continuous welding unit using localized high-frequency current heating. The process is relatively simple, using assembly line operations, resulting in high production efficiency. H-beams can be processed, designed, and combined in any way according to engineering projects, and special specifications can be manufactured to meet the actual needs of specific projects. The specifications of H-beams are designed economically, and their section moment, section coefficient, pressure resistance, and load-bearing capacity are far superior to hot-rolled steel of the same unit weight.
  
  Product Performance Differences:
  Hot-rolled H-beams: Dense internal structure, excellent mechanical properties (strong bending, torsional, and compressive strength), high structural stability, good overall performance, low residual stress, and good surface quality.
  
  High-frequency welded H-beams: Due to the heat-affected zone created by welding, the mechanical properties are affected by the welding quality, and the overall mechanical properties are slightly inferior to hot-rolled steel. However, high-frequency welding results in a smaller heat-affected zone, thinner and more uniform cross-sectional walls, better cross-sectional characteristics, and higher local strength.