Even the best paint or the most advanced powder-coated or galvanised finish is only as good as the surface onto which it is applied. Experience shows that the vast majority of early coating defects on structural steel are not due to the weakness of the coating material, but to inadequate surface preparation. Lasting corrosion protection therefore does not actually begin with painting, but one step earlier, with shot blasting.
It is the surface that determines how long the protection lasts
There are a number of methods to choose from for protection against corrosion and the elements: painting, varnishing, sintering or even galvanising. However, without exception, these are all subject to a single common condition: they are only durable on a perfectly clean surface. If the metal rust, whether it is rust, oil or an old layer of paint, the coating will sooner or later blister or peel off. According to international studies, early coating defects on structural steel occur in approximately 70–80 per cent of these cases can be attributed to inadequate preparation, rather than on the paint itself.
How does sandblasting work?
The shot blasting process is simple and effective: tiny, hard particles are propelled by high-pressure compressed air particles are projected onto the surface to be treated. The particles, striking the surface with high energy, remove the top layer, rust and other contaminants, so that the steel becomes pure metal. The process is still commonly known as ‘sandblasting’, as it was once actually carried out using sand. Today, however, steel grit, corundum, glass, ceramic or dry ice are used instead of sand, depending on the material to be treated and the desired result.
It’s not just about cleanliness: the secret behind the rough surface
However, sandblasting does more than just clean. The impact of the sand particles also gently roughens the surface, creating a pattern of tiny peaks and valleys, known as anchor profile is created. The primer or paint applied later grips onto this microscopic roughness, meaning it adheres much more strongly than it would to a smooth surface.
The right degree of roughness is therefore just as important as cleanliness: this ensures that the coating remains firmly in place.
Measurable quality: SA Grade 2.5
The quality of surface preparation is not a matter of intuition, but rather measurable against a standard. The SA 2.5–3 grade achievable through shot blasting corresponds, according to the international ISO 8501 standard, to a surface that is virtually bare metal, on which only a few faint marks may remain – this is the standard required for long-lasting industrial corrosion protection. It is important that the coating is applied to the cleaned surface as soon as possible – typically within a few hours – before moisture causes rusting to start again.
Sandblasting in crane manufacturing
A crane, a hoist or a steel structure remains in service for decades, often in harsh conditions – and their durability is determined as early as the manufacturing stage, during surface preparation. Shot blasting is also a flexible process: As well as metals, it can also be used to clean surfaces made of wood, stone, glass and plexiglass.
The At Eco-Cranes Sandblasting is an integral part of our comprehensive metalworking services: we carry it out with the same expertise that has made us a recognised leader in the region in the field of crane design and manufacture. Primer, topcoat or powder coating can all be applied perfectly to the metal-clean surface prepared in this way. If you are looking for precise, reliable and durable surface treatment, Please feel free to contact us – The long service life of your crane or hoist starts with a clean surface.
