Blast Profiles – Surface Preparation Specifications for Carbon Steel

Blast Profiles – Surface Preparation Specifications for Carbon Steel

When it comes to surface preparation specifications for carbon steel, one commonly used method is abrasive blasting. Abrasive blasting involves forcibly propelling abrasive materials against the steel surface to remove contaminants and create a profile that promotes effective coating adhesion. The blast profile refers to the roughness or texture created on the steel surface after abrasive blasting.

The selection of blast profiles depends on various factors, such as the type of coating to be applied, the environmental conditions the steel will be exposed to, and the desired level of coating adhesion. Different surface preparation standards provide guidelines for specifying blast profiles. One widely recognized standard is issued by the Society for Protective Coatings (SSPC). The specific standard related to blast profiles is SSPC-SP 10/NACE No. 2, which is commonly referred to as “Near-White Blast Cleaning.”

SSPC-SP 10/NACE No. 2 defines the requirements for surface preparation of carbon steel using abrasive blasting. It specifies a blast profile range of 1.5 to 4.5 mils (38 to 114 micrometers). The term “mils” refers to one-thousandth of an inch, and “micrometers” refers to one-millionth of a meter. This blast profile range is considered suitable for various coating systems, including high-performance coatings.

The surface preparation process to achieve the blast profile specified in SSPC-SP 10/NACE No. 2 typically involves using a clean, dry, and oil-free compressed air system along with appropriate abrasive materials. The selection of abrasive materials depends on factors such as the desired profile, the condition of the steel surface, and the coating system requirements. Common abrasive materials include steel grit, steel shot, aluminum oxide, and garnet.

It’s important to note that blast profiles and surface preparation specifications can vary depending on the specific project requirements, coating systems, and industry standards. Therefore, it’s advisable to consult the relevant coating manufacturer’s recommendations, project specifications, and applicable industry standards to determine the appropriate blast profile and surface preparation specifications for your specific carbon steel application.

We would love to help work through the process to achieve a desired shot blasting profile with you: Here are some steps to get you started:

  1. Identify the desired surface characteristics: Determine the specific surface profile requirements based on factors such as the coating or treatment to be applied, surface roughness specifications, and the intended purpose of the blasted surface.
  2. Select appropriate shot media: Choose the type, size, and hardness of the shot media based on the material being blasted and the desired profile. Shot media options include steel shot, grit, aluminum oxide, garnet, etc. Consider factors such as the material’s impact energy, angularity, and recyclability.
  3. Adjust the shot blasting parameters: Adjust the shot blasting parameters to achieve the desired profile. Key parameters to consider include:
    • Shot velocity: Adjust the shot velocity to control the impact energy and surface roughness. Higher velocities generally result in more aggressive blasting.
    • Shot flow rate: Control the flow rate of shot media to ensure proper coverage and contact with the surface. The flow rate should be sufficient to achieve the desired profile without excessive bounce or ricochet.
    • Blast distance: Determine the appropriate distance between the blast nozzle and the surface being blasted. The distance affects the impact force and pattern distribution. Refer to manufacturer guidelines or conduct tests to find the optimal distance.
    • Angle of attack: Adjust the angle at which the blast nozzle is directed towards the surface. The angle of attack influences the distribution of shot impact and can affect the resulting profile.
  4. Test and adjust: Conduct sample tests to evaluate the achieved profile. If necessary, adjust the shot blasting parameters iteratively until the desired profile is obtained. It may involve modifying shot velocity, flow rate, nozzle angle, or a combination of these parameters.
  5. Ensure proper containment and safety: Set up appropriate containment measures to control the spread of shot media and ensure the safety of personnel and nearby equipment. This can include enclosures, barriers, or ventilation systems. Follow safety guidelines and regulations related to shot blasting operations. LS can custom design a machine to help meet your needs.
  6. Monitor and inspect: Continuously monitor and inspect the blasted surface to ensure consistency and adherence to the desired profile. Use appropriate inspection tools such as profilometers, roughness testers, or visual inspection methods to measure and evaluate the surface characteristics.

By carefully adjusting the shot blasting parameters and evaluating the results, you can gradually achieve the desired shot blasting profile. It’s important to consider the specific requirements of your project, consult with experts at LS Industries, and follow relevant industry standards and best practices throughout the process.

Reach out to the team to see how we can help and learn more.

Steve Slack, West Region Sales Manager

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