Blasting media compared
Mineral media, glass beads, corundum and more – properties and selection criteria.
Read the guideMetal rust removal – thorough, measurable, lasting
Rust comes back if it is not removed completely. Sandblasting creates the defined, clean substrate on which corrosion protection really lasts – here you can read how it works and what Sa preparation grades mean.
The process
Removing rust, mill scale and old paint completely
Painting over rust just seals it in – under the new paint, corrosion keeps working. Sandblasting, by contrast, removes rust, mill scale and old coatings completely, even in corners, on edges, in profiles and weld seams that wire brushes and grinders never reach cleanly.
There is a second, often underestimated effect: the blast media roughens the surface in a defined way. This roughness profile acts like an anchor for the subsequent primer or powder coating – the coating keys mechanically into the steel and lasts years longer as a result.
Mill scale also has to come off completely, even if it looks firm and harmless: the blue-grey layer from the rolling mill is electrochemically nobler than the steel beneath it – if it stays under the coating, the steel preferentially keeps rusting at its edges. De-scaling by blasting is therefore mandatory wherever lasting protection is required.
Standards made simple
Sa preparation grades simply explained
How clean a blasted steel surface is, is described by the ISO 8501-1 standard using so-called Sa preparation grades. They appear in almost every coating specification – here is how to read them:
- Sa 1: Loose rust, loose mill scale and loose coatings are removed – the basic cleaning for subordinate purposes.
- Sa 2: Thorough blast-cleaning – firmly adhering residues may remain to a limited extent.
- Sa 2½: Very thorough blast-cleaning – only light shadows remain visible. The standard for high-quality corrosion protection and the most common specification from coaters.
- Sa 3: Bare metal with a uniform metallic appearance – the highest grade for special requirements.
For most primers and powder coatings, Sa 2½ is specified. Tell us what your coater requires – we blast to the specified grade.
After blasting
Now speed matters: the corrosion protection
Freshly blasted steel is unprotected – depending on humidity, the first flash rust forms within just a few hours. That is why every rust-removal project needs a plan for what follows immediately: prime or coat promptly, before the surface tarnishes again.
We are therefore happy to coordinate our work directly with your painter or powder coater – on timing and on the specified preparation grade including the roughness profile. That way each step meshes cleanly with the next, and the new protective build-up delivers what it promises.
Applications
Typical rust-removal projects
From the garden gate to the hall structure – we remove rust directly on site or in your hall:
- Steel beams and hall structures
- Railings, fences, gates and balconies
- Agricultural machinery and implements
- Machine, plant and vehicle parts
Frequently asked questions
Frequently asked questions on this topic
Sa 2½ still permits light shadows on the surface, Sa 3 demands uniformly bare metal. For the vast majority of coatings Sa 2½ is sufficient – Sa 3 is only specified for special requirements and takes noticeably more effort.
As quickly as possible – depending on humidity, flash rust forms within hours to a few days. Ideally, priming happens the same or the next day. That is why we like to time our work directly with your coater.
Yes, we work mobile in your hall or on your site – with covers and protection for the surroundings. Large structures are blasted section by section, on request outside your production hours.
Keep reading
Related topics
Metal & steel
Our service for metal surfaces at a glance: rust removal, paint stripping, de-scaling.
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Rust has to go?
From railings to hall structures: send us photos – we will name the preparation grade, the workflow and a fixed price.