Super Detailed Instructions For Rust Removal Of Steel Structures To Sa2.5 Level [Equipment Construction]

Super detailed instructions for rust removal of steel structures to Sa2.5 level [Equipment Construction]

People who are engaged in steel structure anti-corrosion should be very clear that the Sa2.5 standard belongs to the higher level of rust removal requirements. However, the steel structure rust removal to Sa2.5 level standard is very detailed [Equipment Construction]. Indeed, many people are confused about the specific difference between the two levels of Sa2.5 and Sa2. At the same time, a considerable number of people do not know what kind of machinery and equipment should be equipped in this case.

Core definition of Sa2.5 standard

Sa2.5 refers to a standard state stipulated in GB/T8923.1-2011, which is called very thorough spray or projection rust removal. In this state, visible grease, dirt, scale, rust and old paint films are not allowed to appear on the surface of the steel.

The remaining traces, this thing, are only allowed to be dot-like. Or the striped kind. This stain must be mild. If you pick it with your hands, it won't come off. This is something important, but it is more strict than Sa2. This is the key dividing line.

The level difference between Sa2.5 and Sa1 and Sa2

For Sa1, it only requires that the grease and dirt cannot be clearly seen, and the oxide scale that is not strong enough can still be allowed to remain. But the requirements of Sa2 are different. The attachments must be basically removed. If there are any residues, they must be firmly attached to it.

Sa2.5 reduces the residue to the "slight stain" level. In the 2024 Ministry of Housing and Urban-Rural Development project quality inspection, large steel structure projects have included Sa2.5 in the hard acceptance terms.

How to configure sandblasting and rust removal equipment

The sandblasting machine relies on the power of compressed air to spray quartz sand or river sand onto the surface of the workpiece at high speed. It is not limited by the size of the workpiece. For example, H-shaped steel with a length of more than ten meters, or embedded parts that have been poured, can be processed.

During the actual measurement at a steel structure factory in Nantong, Jiangsu, the equipment configuration used was a medium-sized sandblasting machine, equipped with a gas storage tank with a capacity of 220 liters, and an air compressor with a power of 130 kilowatts. Under such conditions, the entire operation process takes about 4 hours to process a steel plate with an area of ​​about 500 square meters, after which the steel plate can meet the standards required for acceptance.

Applicable scenarios for shot blasting and rust removal equipment

The automatic pass-through shot blasting machine uses steel shot to hit the workpiece. It is very fast and the processing effect is very uniform. However, one thing to note is that the length of the workpiece cannot exceed the 6 meters limit of the material box and the width cannot exceed the 2.5 meters limit of the material box.

A manufacturer from Jining, Shandong Province, has launched a treatment equipment model Q3210 that will be sold externally in 2025. The processing capacity of this machine can reach up to 12 tons per minute, so it is very suitable for components that require batch riveting and welding. When using this equipment for operations, the processing cost of a single product can be reduced by about 30% compared to the traditional sandblasting process.

Practical points for selection

When checking the size of the workpiece, if the size exceeds the range, then you can only go through the sandblasting process; for items in small batches, it will be more cost-effective to choose shot blasting; after entering 2025, new environmental protection regulations require that sandblasting operations must be accompanied by the use of closed-loop dust removal equipment.

The shot blasting machine depends on the number of blasting heads. Only if it reaches four or more can the processing result be guaranteed to be Sa2.5 level uniformity. If not, rust will easily be left in the corners.

Common Misunderstandings and Remedies

On the construction site, someone took an angle grinder to grind it, and then claimed that it reached the Sa2.5 standard. In fact, through manual rust removal, the highest level can only reach St2 level. When it comes to acceptance , use a ruler to visually measure the density of stains, and you will come to the conclusion that it is unqualified.

If you want to rework, you will need to use a sandblasting machine or a shot blasting machine. For those cases where primer has been sprayed, the old paint layer must be sanded off and cleaned first, and then the rust must be removed. In this case, the construction period will be extended by two or three days, and the material cost will be at least doubled.

How old is the batch of riveted weldments in your hand, and how much is the quantity? Think about it for yourself, whether sand blasting is more cost-effective than shot blasting, or whether shot blasting is more cost-effective than sand blasting. Please share your opinion in the comment area. If you think this makes sense, give it a like and forward it to your fellow workers.