Steel Structure Repair Does Not Want Sandblasting And Rust Removal

Steel structure repair does not want sandblasting and rust removal

In the repair project of riveted parts of the hull, sandblasting and rust removal alone consumes nearly half of the budget and will also delay the completion of the entire project.

Why is sandblasting rust removal scolded?

In the high bulkhead position, in the narrow pipe gallery, in the built and put into production dock, the sandblasting machine cannot be accommodated at all, so it cannot be inserted at all. Sand and dust fell to the workstation area next door. Because the environmental protection department inspected and directly issued a fine, the construction team was living in fear every day.

The price quotation of sandblasting per square meter is about 30 yuan to 50 yuan. If the total area is 100 square meters, the total cost is between 3,000 yuan and 5,000 yuan. However, the rental fee of the equipment, the labor cost and the loss caused by the shutdown need to be calculated separately. In many projects related to rivet weldment repair, the amount of funds consumed by rust removal alone accounts for more than 60% of the entire budget.

What exactly does rust coating rely on?

In Tianjin's epoxy anti-rust primer, two active ingredients are added. The penetrant will penetrate into the micropores of the rust layer and displace the water vapor and oxygen; while the other rust converting agent will complex with iron oxide, eventually forming a black inert protective film.

The base material does not need to be polished until the metallic luster is exposed. Use a wire brush or angle grinder to remove floating rust, bulging old paint and oil stains. It is enough to meet the St2 level standard. The paint film is firmly attached to the transformed rust layer, the adhesion is first level, and the salt spray resistance time is more than 500 hours.

Three steps for construction

The first step is to use an angle grinder to clean off the loose rust, oil stains and peeled paint. The second step is to brush or roll the primer directly after the treatment, and the dry film thickness must be controlled within the range of 80 to 100 microns. The third step is to wait until the coating is completely dry, and then cover it with an epoxy mica topcoat or polyurethane topcoat.

The whole process is completed by one person alone with a brush. There is no need to wait for the substrate to dry completely before starting. Even if the relative humidity reaches 85%, it can still be used.

According to the sandblasting method in the past, it would have taken a full eight hours to complete a process, but now, it only takes two hours to complete the work, so that the entire workshop does not have to stop production to wait for construction time.

Calculate how much money you can save

Regarding the comparison of 100 square meters, the sandblasting plan includes materials and labor costs of about 4,500 yuan, and the schedule takes two days, while the rust coating plan has a complete set of materials and processing costs of only about 1,500 yuan, and can be completed in half a day. This alone saves 3,000 yuan in cost.

It is also necessary to calculate the hidden costs. Once the shipyard stops production even for just one day, the loss in production rhythm can easily exceed 10,000 yuan. The technology of rust coating does not require cutting off the power supply or stopping the production line. If these factors are also taken into account for accounting, the final gap between the two will become even greater.

Which scenarios are most suitable for

Hull rivet weldments, deck pipeline brackets, bulkhead reinforcements, port booms, wharf trestles, all are applicable as long as they are at high places, or in narrow gaps, or in places where production cannot be stopped, or where dust cannot be raised.

This entire set of processes can also be used in the primer construction process in the workshop of newly built ships before they officially leave the factory. Since this method can omit the sand throwing assembly line, the overall construction cycle is naturally shortened by about two to three days. Currently, many shipyards in China have begun to use it in batches.

Frequently asked questions explained once

Some people have raised questions about whether painting can be done directly if the rust layer is too thick. To be honest, when the thickness of the rust layer exceeds 200 microns, it is recommended that you remove it first, otherwise cracking will easily occur because the coating is too thick. After cleaning the rust, it is best to control the thickness of the rust layer within 50 microns. This is the most ideal situation.

In addition, there are also some concerns about water resistance. After actual measurement in a salt spray chamber, the results showed that it can last for 500 hours, and the film layer did not blister or fall off. In a normal marine atmospheric environment, within a ten-year maintenance cycle, there is basically no need for rework.

Are you still spending a lot of money unnecessarily on arranging sandblasting operations for the repair work of riveted and welded components of the hull? Please talk about the alternatives you know in the comment area. If you think this method is useful, like it and forward it to your colleagues.