JPH04308751A - Method for repairing coated steel material - Google Patents

Abstract

PURPOSE:To improve the appearance inferiority due to the brush mark, iron mark and film running at the time of the application of repairing paint in repairing the fault part of a coated steel material. CONSTITUTION:A coating fault part is cut out into a circular or rectangular shape by a cut-out jig and a cured film of the same system as a non-repaired part preliminarily processed into a circular or rectangular shape is laminated to the cut-out part using repairing paint with solvent content of 5% or less of the same system as the non-repaired part as an adhesive layer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing coated steel materials, and its purpose is to prevent corrosion of coating flaws that occur during transportation and construction of coated steel materials.

0002

[Prior art and problems to be solved by the invention] Conventionally,
Generally, coating defects on coated steel are repaired by brushing or troweling with a high-viscosity repair paint at a relatively low speed. In addition, repair paints are designed to have a high viscosity in consideration of the sagging properties of the paint film, and at the same time add stickiness to the paint, so when brushed or troweled, brush marks and trowel marks may remain. Particularly when repairing vertical parts, poor appearance of the paint film due to sagging occurs. In addition, from the viewpoint of repair painting workability, the paint has a relatively low curing speed, so it takes time to handle it when repairing before construction, and it is difficult to handle the coating material after construction, for example when repairing seawater splash areas. If the parts come into contact with seawater before they harden, the coating may fall off and corrosion protection cannot be ensured. In addition, non-repaired areas are covered at the factory.
Since spray painting is generally applied, the coating has a glossy appearance, whereas repaired areas coated with a brush or trowel have a matte surface, which is undesirable because the appearance of the unrepaired area and the repaired area is different. Other anti-corrosion methods include a method using petrolatum tape and cement mortar lining using FRP formwork, but these methods are difficult to apply to complex structures and have the drawbacks of high cost.

0003

[Means for Solving the Problems] The present inventors have completed the present invention as a result of intensive studies regarding a method for repairing painted steel materials. In other words, depending on the size of the flaw, the covered flaw part of the painted steel material is cut out in a circular and/or square shape using a cutting jig, and after the cut out part is prepared as a base, a repair paint of the same type as the non-repaired part is used as an adhesive. , is a method of repairing painted steel materials that is characterized by pasting together a cured coating film with a similar solvent content of 5% or less to non-repaired areas that have been previously processed into circular or square shapes.This method eliminates the drawbacks of conventional repair methods. The poor appearance and corrosion resistance of the repaired surface were improved.

[0004] The invention will be explained in detail below. The cutting jig of the present invention has a circular or square shape and is made of steel, has a size slightly larger than the circular or square cured coating film to be applied to the flaw, and punches out with a hammer or the like. The cut cross section of the coating film may be vertical or tapered, but in order to improve the adhesion between the cured coating film and the non-repaired coating film,
It is best to taper the cross section of the non-repaired coating film. The purpose of surface treatment is to remove rust from the steel base such as keren, glider, wire brush, and blast, and to roughen the unrepaired areas that are in contact with the repaired areas. The degree of rust should be SIS Sa2.5 or higher, and the roughness of the non-repaired areas should be as rough as possible. Also, if a primer is required after removing rust from the iron base due to the characteristics of the repair paint, apply it before applying the repair paint. The repair paint used as an adhesive is a paint of the same type as the non-repair area.
Use a low-solvent paint that has excellent compatibility with unrepaired areas and repaired cured coatings and has a solvent content of 5% or less. If a paint with a solvent content of more than 5% is used, the solvent will remain between the unrepaired area and the repaired cured paint film, impairing the adhesion between the unrepaired area and the repaired cured paint film. Preferably, the solvent content should be as low as possible. As a paint system,
Any paint system such as epoxy or polyurethane can be used, but polyurethane paint is preferred because it can be cured even in winter and is completely solvent-free. The repair cured coating is
Spray paint in advance with the same paint used for factory painting on non-repaired areas, and after curing, cut out circular and/or square shapes. The cross section of the cured coating film may be vertical or tapered. For example, if a non-repaired area is tapered, the cross section will be tapered to match the non-repaired area. The thickness of the repaired cured coating varies depending on the thickness of the non-repaired area, but since the adhesive repair paint is applied between the non-repaired area and the repaired cured coating, the thickness of the non-repaired area will vary. 20% to 80% is good. If the film thickness is less than 20%, the film thickness of the repair cured coating is too thin and wrinkles will occur on the coated surface, damaging the appearance, and if the film thickness is 80% or more, the repair cured coating film will not work as an adhesive. Since the thickness is thin, adhesion with the repair cured coating is not sufficient. Preferably, a film thickness of about 50% is good because the film thickness can be adjusted according to the film thickness of the non-repaired area, and the repair paint as an adhesive will sufficiently penetrate into the repair cured coating film. be.

[0005] After bonding the repair cured paint film, if uncured paint as an adhesive is visible on the paint film surface, it is scraped off with a trowel or the like to adjust the appearance of the paint film. Hereinafter, the present invention will be explained in more detail according to Examples.

[0006]

[Example] Example 1 A hot rolled steel plate measuring 6 mm x 100 mm x 100 mm was subjected to grit blast treatment, coated with a primer, then coated with polyurethane paint to a film thickness of 2.5 mm, and completely cured. Cut out the coated surface with a punched metal fitting with a diameter of 50 mm to create a scratch, and then grind the steel surface with a hand grinder.
After finishing the cross section with a Sa of 2.5 or more and a 45 degree taper, a 50 μm thick primer was applied and after curing, a solvent-free polyurethane repair paint was applied using an iron spatula to a thickness of about 2.5 mm. Immediately, apply a cured polyurethane film with a diameter of 45 mm and a film thickness of 0.5 mm so that it is at the same height as the non-repaired surface, and use a trowel to remove the repair paint that has been pushed out from between the non-repaired surface and the surface of the repaired cured film. The scraped surface was adjusted.

Example 2 A hot-rolled steel plate measuring 6 mm x 100 mm x 100 mm was grit blasted, coated with a primer, then coated with polyurethane paint to a thickness of 2.5 mm, and completely cured. Cut out the coated surface with a punched metal fitting with a diameter of 50 mm to create a scratch, and then grind the steel surface with a hand grinder.
After finishing the cross section with a Sa of 2.5 or higher and tapering the cross section by 45 degrees, a 50 μm thick primer was applied and after curing, a solvent-free polyurethane repair paint was applied using an iron spatula to a thickness of about 1 mm. Immediately, apply a cured polyurethane coating with a diameter of 45mm and a thickness of 2mm to the same height as the non-repaired surface, and use a trowel to remove the repair paint that has been pushed out from between the non-repaired surface and the repaired cured coating surface. Adjusted the scraped surface.

Example 3 A hot-rolled steel plate measuring 6 mm x 100 mm x 100 mm was grit blasted, coated with a primer, then coated with polyurethane paint to a thickness of 2.5 mm, and completely cured. Cut out the coated surface with a 50mm x 50mm punching metal fitting to create a flaw, then grind the steel surface with a hand grinder.
After finishing the cross section with an IS Sa of 2.5 or higher and a 45 degree taper, a 50 μm thick primer was applied and after curing, a solvent-free polyurethane repair paint was applied using an iron spatula to a thickness of about 1.5 mm. Immediately, apply a cured polyurethane coating of 45mm x 45mm with a thickness of 1.25mm to the same height as the non-repaired surface, and remove the repair paint that has been pushed out from between the non-repaired surface and the repaired cured coating. The surface was adjusted by scraping with a trowel.

Example 4 A hot-rolled steel plate measuring 6 mm x 100 mm x 100 mm was grit blasted, coated with a primer, and then coated with epoxy paint to a thickness of 2.5 mm and completely cured. The coated surface was cut out using a punching metal fitting with a diameter of 50 mm to create a flaw, and then the flaw was ground using a hand grinder to grind the steel surface into SIS S.
After finishing the cross section with a 45 degree taper of a2.5 or more, an epoxy repair paint with a solvent content of 4% was applied using an approximately 1.5 mm iron spatula. Immediately, a film thickness of 1.25 mm with a diameter of 45 mm
A cured epoxy coating film of mm was pasted to the same height as the non-repaired surface, and the repair paint extruded to the surface from between the non-repaired surface and the repaired cured coating surface was scraped off with a trowel to adjust the surface.

Example 5 A hot rolled steel plate measuring 6 mm x 100 mm x 100 mm was grit blasted, coated with a primer, and then coated with epoxy paint to a thickness of 2.5 mm and completely cured. Cut out the coated surface with a 100mm x 50mm metal punch to create a flaw, then use a hand grinder to grind the steel surface into SI.
S Sa2.5 or more, after finishing the cross section with a 45 degree taper, apply approximately 1.5 mm of epoxy repair paint with a solvent content of 4%.
It was applied using an iron spatula. Immediately, 95mm x 45mm
Apply a cured epoxy coating film with a thickness of 1.25 mm to the same height as the non-repaired surface, and use a trowel to scrape off the repair paint that has been extruded to the surface from between the non-repaired surface and the repaired cured coating surface. adjusted.

Comparative Example 1 A hot-rolled steel plate measuring 6 mm x 100 mm x 100 mm was subjected to grit blasting, coated with a primer, then coated with polyurethane paint to a thickness of 2.5 mm, and completely cured. Cut out the coated surface with a punched metal fitting with a diameter of 50 mm to create a scratch, and then grind the steel surface with a hand grinder.
After finishing the cross section with a Sa of 2.5 or more and a 45 degree taper, a 50 μm thick primer was applied and after curing, a polyurethane repair paint with a solvent content of 10% was applied using an approximately 1.5 mm iron spatula. Immediately, apply a cured polyurethane film with a diameter of 45 mm and a film thickness of 1.25 mm so that it is at the same height as the non-repaired surface, and use a trowel to remove the repair paint that has been pushed out from between the non-repaired surface and the surface of the repaired cured film. The scraped surface was adjusted.

Comparative Example 2 A hot-rolled steel plate measuring 6 mm x 100 mm x 100 mm was subjected to grit blasting, coated with a primer, then coated with polyurethane paint to a thickness of 2.5 mm, and completely cured. Cut out the coated surface with a punched metal fitting with a diameter of 50 mm to create a scratch, and then grind the steel surface with a hand grinder.
After finishing the cross section with a Sa of 2.5 or higher and a 45 degree taper, a 50 μm thick primer was applied and after curing, a solvent-free polyurethane repair paint was applied using a 2.5 mm iron spatula. The sample prepared above was immersed in 3% saline at 60°C,
After 500 days of immersion, adhesion was measured using the pull-off method.
External appearance was observed. The results are shown in Table 1.

[0013]

[Table 1]

[0014]

[Effects of the Invention] According to the present invention, the appearance of the repaired area is as shiny as that of the non-repaired area, and the paint film sagging on the vertical and ceiling areas, which has been a problem up until now, can be avoided. Without,
Repairs were possible. Furthermore, since the repaired part according to the present invention does not lose its adhesion even in a long-term salt water immersion test, it can be expected to have the same long-term durability in marine areas as the unrepaired part.

Claims (1)

[Claims] Claim 1: Cut out the coated flaw part of the painted steel material into a circular and/or square shape using a cutting jig depending on the size of the flaw, and after the cut out part is subjected to surface treatment, the same solvent content as the non-repaired part is used. A method for repairing coated steel materials, which is characterized by pasting together a cured coating film of the same type as a non-repaired area that has been previously processed into a circular and/or square shape, using a repair paint containing 5% or less as an adhesive.