Posted by Ruby Popple on 10th Jul 2024
Wet blasting is a highly effective method for cleaning and preparing metal surfaces. By combining abrasive particles with water, wet blasting minimises dust, reduces heat generation, and produces a smooth finish. However, this process introduces a new challenge: flash rusting, when treating ferrous substrates.
In this blog post, we will delve into the causes of flash rusting and provide you with practical strategies to prevent it. From understanding the science behind flash rusting to exploring various prevention methods, our comprehensive guide will equip you with the knowledge and tools needed to keep your metal surfaces pristine and rust-free after wet blasting. Whether you are a professional in the industry or a DIY enthusiast, these tips will help you achieve the best possible results in your projects.
What is flash rusting, and why does it happen?
Flash rusting is where corrosion appears on the surface of a metal, which occurs due to the electrochemical reaction between iron in the metal, oxygen in the air, and moisture from the water used in the wet blasting process.
This type of rusting can happen within minutes to hours after wet blasting and can remove or damage the metal’s protective passive oxide layer.
This leaves the metal substrate unprotected and vulnerable to corrosion attack as it becomes exposed to air and moisture.
As a result, metal that is cleaned using wet blasting methods has the potential to develop rust rapidly, which can undermine the effectiveness of the surface preparation and negatively impact the performance of applied coatings.
How can I prevent flash rust?
- Inhibitors in the blasting water: One of the most effective ways to prevent flash rust is to add corrosion inhibitors to the water used during the blasting process. These inhibitors are designed to purge moisture from the surface and work to slow the rusting process. Inhibitors commonly used include passivators, salt removers and surfactants.
- Check the water quality: The water quality is extremely important if you wish to prevent flash rust. If you do find that your surface has rusted, it is likely due to relatively high concentrations of harmful chlorides and other impurities found in the water. Water filtered by distillation or reverse osmosis can help prevent the probability of flash rust formation. At high levels of purification, the use of filtered or distilled water can also reduce or eliminate the need for other protection methods.
- Surface quality: Is the surface free of contaminants? Contaminants present on the surface of the metal substrate can also contribute to the formation of flash rust. These contaminants, which are often left on the surface after wet or dry blasting, can draw moisture from the humidity in the surrounding environment to create a corrosion cell. There are several origins for this, including preexisting rust. Contaminants may also be deposited on the surface by rain, airborne pollutants or the steel forging process.
- Immediate post-blast drying: Rapid drying of the blasted surface is crucial to prevent flash rusting. Use high-pressure air blowers to remove moisture from the surface immediately after blasting. Ensuring the surface is completely dry will minimise the risk of rust formation.
- Apply a protective coating: Applying a protective coating immediately after drying can prevent moisture from contacting the metal surface. There are several types of coatings available: primer coatings, which are designed for metal surfaces and can be applied directly after blasting to provide a barrier against moisture, and temporary protective coatings, these are specifically formulated to provide short-term rust protection until the final coating is applied.
- Control the environment: Working in a controlled environment where humidity and temperature can be regulated can significantly reduce the risk. In situations where environmental control is not possible, using dehumidification equipment can be an effective solution. Portable dehumidifiers can be placed in the vicinity of the blasted surface to reduce ambient moisture levels and prevent rust formation.
- Regular monitoring and inspection: Regularly inspect the blasted surfaces for signs of rust formation. Early detection allows for quick intervention before the rust can progress.
- Use rust converters if needed: If flash rust does occur, rust converters can be used to treat the affected areas. Rust converters chemically transform rust into a stable compound that can be painted over. However, it’s best to prevent rust formation from the start to avoid additional steps and potential surface imperfections.
Conclusion
Preventing flash rusting after wet blasting requires a combination of techniques and careful planning. By implementing these strategies, they will not only preserve the quality of the blasted surface but also extend the lifespan of your metal structures and components. Embrace these methods in your wet blasting process to achieve optimal results and maintain the integrity of your work.
Ready to transform your cleaning and surface preparation process? Discover the efficiency and effectiveness of our wet blasting solutions, including UHP equipment.
Contact us today at sales@airblast.co.uk or call +44 1778 560650 for a free consultation and find the perfect solution for your business needs.
