Sandblasting Metal Abrasives Suppliers

How do metal abrasives impact the adhesion of paint or coatings applied after sandblasting?
Metal abrasives, such as steel grit or shot, are commonly used in the sandblasting process to remove old coatings, rust, or other contaminants from metal surfaces before the application of paint or coatings. The impact of metal abrasives on adhesion can be both positive and negative, depending on various factors.

Firstly, metal abrasives create a rough profile on the surface being sandblasted. This profile enhances the mechanical adhesion of paint or coatings by providing a textured surface for the paint to grip onto. The roughness increases the surface area available for the paint to adhere, thus improving the bond strength between the surface and the coating. This is especially beneficial for coatings that rely on mechanical interlocking, such as epoxy coatings.
Secondly, metal abrasives can achieve a high degree of surface cleanliness and remove contaminants effectively. This is crucial for ensuring proper adhesion of the paint or coatings to the surface. Abrasives like steel grit can remove rust, corrosion, old paint, and other foreign substances that may hinder adhesion. By eliminating these contaminants, the metal is prepared for optimal coating adhesion, which leads to better coating performance and longevity.

However, there are also potential negative impacts of metal abrasives on adhesion. One of the main concerns is the creation of sharp-edged profiles or micro-indentations on the surface, especially with harder abrasives like steel shot. These sharp edges can act as stress concentration points in the coating, potentially leading to premature coating failure. To mitigate this issue, it is often recommended to follow up the sandblasting process with a sweep blast using a less aggressive abrasive to smooth out the surface and reduce stress concentration.
Another consideration is the issue of cleanliness after sandblasting. Metal abrasives can introduce ferrous contaminants onto the surface, which can cause adhesion problems if not properly addressed. These contaminants can react with moisture in the environment, leading to rust or other forms of corrosion that can compromise coating adhesion. Thorough cleaning and proper surface preparation, including the removal of any residual abrasive particles or contaminants, are critical to ensure good coating adhesion.

How do the particle size and shape of metal abrasives influence their performance in sandblasting?
Particle Size:
The particle size of metal abrasives affects the surface profile created on the substrate. A surface profile refers to the roughness or texture of the surface after sandblasting. Different applications require different surface profiles, and the choice of particle size should align with the desired profile.
Coarse particles remove surface contaminants more rapidly but create deeper and rougher profiles. Conversely, fine particles remove contaminants more slowly but produce shallower and smoother profiles. It is crucial to match the particle size with the intended surface preparation requirements to achieve proper adhesion of coatings.
Additionally, the particle size affects the blasting pattern width and the coverage area. Coarser particles tend to cover a smaller area per unit of time, while finer particles provide wider coverage. Thus, the choice of particle size determines the efficiency and productivity of the sandblasting process.

Particle Shape:
The shape of metal abrasives influences the efficiency of sandblasting and the resulting surface profile. There are generally two types of shapes: angular and rounded.
1. Angular Abrasives: Abrasives with angular shapes, such as steel grit, create a more aggressive cutting and impact action on the surface. Due to their sharp edges, they can remove coatings and contaminants more effectively. Angular abrasives are particularly useful for surfaces with heavy rust or stubborn coatings. However, they also tend to create deeper surface profiles.
2. Rounded Abrasives: Abrasives with rounded shapes, such as steel shot, have a smoother and less aggressive impact on the substrate. Their rounded edges reduce the depth of the surface profile, making them suitable for applications that require a smoother finish. Rounded abrasives are commonly used for surface preparation on delicate or sensitive materials.