Painting Steel

The effective life of a paint applied to a steel surface is dependent on steel surface preperation methods and quality.

1. Introduction

Steel surfaces need to be treated to prevent corrosion over the lifespan of the product. Surface preparation is the first step. Adhesion and the performance of the coating improves when impurities on the material surface are removed and the surface is properly cleaned.

Different steel structure paint types require different pre cleaning. For steel structures and components this pre cleaning usually involves operations like grinding and blasting.

2. Surface Preparation Methods
  • Shot blasting

Shot blasting is a mechanical cleaning process that uses spheres of material to remove oxides and other impurities from the surface of metal. Shot blasting belongs in the same family of abrasive blasting processes such as sandblasting and grinding.

Figure 1 Shotblasting and Primering

This abrasive treatment method uses a device similar to a spinning wheel to centrifugally accelerate media and blast it against a surface.

One of the main benefits of shot blasting is that the operation does form very little dust making it a safer operation than sandblasting.

  • Sandblasting

Sandblasting is a surface cleaning process that involves the use of an air compressor and a sandblasting machine to spray sand particles under high pressure towards a metal surface. As the sand particles strike the surface, they create a smoother and more even surface. Sand is rough and gritty. Due to its characteristics, it’s able to remove excess or unwanted material on a surface.

Figure 2 Sandblasting

Sands containing crystalline silica can cause serious or fatal respiratory disease therefore sandblasting requires appropriate dust protection equipment.

Sandblasting is still the most common and preferred abrasive treatment method. It is an economical equipment system to purchase, easier to operate and offers excellent surface finishing.

Sandblasting can be used for a range of purposes such as remove pain, stripping pavements, polishing surfaces, removal of dirt.

  • Power Tool Cleaning

Power tool cleaning is also an option when blasting methods are not sufficient. Impact and rotary tools can achieve excellent surface preparations.

Figure 3 Power Tool Cleaning

Impact cleaning tools scrape and chip away rust and paint. However, they also run the risk of physically damaging metal surface and causing additional work.

Rotary cleaning tools consist of an abrasive material that spins on a disk at high velocity. These tools can clean surface quickly, but they might leave grease and oil on the metal surface, requiring solvent pre-cleaning.

Hand tool cleaning becomes necessary when the work piece have inaccessible places such as small corners.

3. Conclusion

Surface preparation is just as important as the selecting the right paint for the corrosion protection of the metal. Determining the right surface preparation method is essential for a long-lasting, effective coating system. For steel structures, usually, a combination of using multiple surface preparation methods is required to achieve this goal.

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