JP2016199777A - Steel material for coating with excellent anticorrosion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel material for coating with excellent anticorrosion, capable of preventing corrosion by an effect of a corrosive action such as seawater or airborne sea salt particles.SOLUTION: In a steel material for coating, a base steel material includes: 0.04-0.30% C, 0.05-1.0% Si, 0.1-2.5% Mn, over 0% and 0.04% or less P, over 0% or 0.04% or less S, 0.005-0.20% Al, 0.05-1.0% Cu, 0.05-1.0% Cr, 0.001-0.015% N, and in addition, one or two kinds of 0.005-0.1% Ti and 0.005-0.1% Nb. A surface layer thereof includes 20-200 g/mZn, 0.3-20.0 g/mCu and in addition, one or two kinds of 0.3-20.0 g/mCr and 0.3-20.0 g/mNi.SELECTED DRAWING: None

Description

  The present invention relates to a steel material for coating used in steel structures such as ships, marine structures, and bridges, and more particularly to corrosion resistance used in a corrosive environment mainly caused by seawater or flying sea salt particles. It relates to an excellent steel material for painting.

  Steel is widely used as a structural member for various structures, but when used as a structural member for structures affected by seawater such as ships, marine structures, bridges, etc., steel is subject to corrosive effects such as seawater. As a result, there is a problem that the strength of the structure may decrease due to a reduction in plate thickness or perforation.

  Corrosion due to seawater of such steel materials can be prevented by electro-corrosion when steel materials are used only in parts that are completely immersed in seawater, but they are not always immersed in seawater near the sea surface or near the sea surface. Electrocorrosion protection does not act on the part, and it will be exposed to a severe corrosive environment caused by splash of seawater, which is difficult to prevent with electrocorrosion.

  Also, when steel is used as a structural member for ship ballast tanks, it is necessary to inject and discharge seawater into the ballast tank according to the load, so the inner surface is always immersed in seawater. In other words, a sufficient anticorrosive action cannot be obtained.

  Furthermore, since structures such as iron bridges close to the coast are exposed to atmospheric corrosive environments caused by flying sea salt particles, even when steel is used as a structural member for such structures, application of anticorrosion is not necessarily required. Often not valid.

  In this way, the application of cathodic protection is not always effective for ships, marine structures, bridges, and other structures that are affected by seawater. Often used. Various anti-corrosion paints such as epoxy resin, chlorinated rubber, acrylic resin film, urethane resin, and fluororesin can be listed as paints used for anti-corrosion coating. In some cases, these are used in multiple layers.

  However, the anticorrosive coating film may be damaged by deterioration with time due to ultraviolet rays or some external mechanical action. Since the steel material corrosion progresses in the heel part of such an anticorrosion coating film, regular maintenance is required. However, in structures such as ships, offshore structures, bridges, etc., there are high places where it is necessary to build scaffolds for inspection and maintenance of the anti-corrosion coating, underwater, or structurally intricate places. There are many places where coating inspection and maintenance are not easy. Thus, from the viewpoint of ensuring safety and reducing the maintenance load, the suppression of corrosion starting from the buttocks of the anticorrosion coating film is a very important technical issue.

  As a countermeasure to such a problem, the technology that improves the corrosion resistance of the steel material itself by adjusting the chemical composition of the steel material and improving the manufacturing method, and contributes to the corrosion inhibition of the buttock of the anticorrosion coating film is disclosed in Patent Document 1, Many have been proposed by 2 etc. Although the corrosion resistance of steel for coating is certainly improved by adopting these techniques, the current situation is that further improvement in corrosion resistance is required.

  In particular, in ship ballast tanks, the amount of corrosive wear per year can reach as much as 1 mm at the point where the paint film is peeled off. Is strongly desired. In recent years, there is an increasing demand for extending the service life of ships, and there is an increasing need for extending the service life of the ballast tank, which is most severely deteriorated in ships, exceeding the current 15 years.

  In particular, in recent years, clean energy that does not emit carbon dioxide, a greenhouse gas, has been attracting attention from the viewpoint of conservation of the global environment. Wind power generation, ocean wave power generation, tidal current / sea current power generation, temperature difference power generation, Development of power generation technology such as solar power generation is underway.

  These use environment conditions are assumed to be more severely corrosive than the conventional beach and seawater environment, and a corrosion resistance / corrosion prevention technique applicable to more severe environment conditions is required. In addition, in order to realize these, maintenance work such as inspection and repainting of steel materials is difficult, and from the viewpoint of life cycle cost, the need for further extension of corrosion protection life has been raised. It is desired to develop a technique for improving the corrosion resistance of steel for painting.

JP 2010-229526 A JP 2012-92404 A

  The present invention has been made in view of the above-described conventional situation, and provides a steel material for coating excellent in corrosion resistance capable of suppressing corrosion due to the influence of corrosive action such as seawater and flying sea salt particles. Is an issue.

  In particular, in steel plates, steel plates, and shaped steels with a thickness of 3 mm or more, even if they are used as structural members for structures under seawater corrosive environments or corrosive environments mainly caused by flying sea salt particles, there are problems with corrosion resistance. An object of the present invention is to provide a steel material for coating which does not generate corrosion and has excellent corrosion resistance.

The steel material for coating having excellent corrosion resistance according to the present invention is a steel material for coating including a base steel material and a surface layer formed on the surface of the base steel material, and the base steel material is in mass%, and C: 0.04. -0.30%, Si: 0.05-1.0%, Mn: 0.1-2.5%, P: more than 0% and 0.04% or less, S: more than 0% and 0.04% or less, Al: 0.005-0.20%, Cu: 0.05-1.0%, Cr: 0.05-1.0%, N: 0.001-0.015%, and Ti: 0.005 to 0.1%, Nb: Any one or two of 0.005 to 0.1%, the balance being a steel material composed of Fe and inevitable impurities, and the surface layer is ^{, Zn: 20~200g / m 2,} Cu: with containing ^{0.3~20.0g / m 2, Cr: 0.3~20.0g} / m 2, N : Characterized in that it contains either one or two 0.3~20.0g / ^{m 2.}

  Moreover, the said base steel material is further mass%, Ni: 0.01-6.0%, Co: 0.01-5.0%, Mo: 0.01-2.0%, W: 0.0. It is preferable to contain any 1 type or 2 types or more of 01-2.0%.

  Further, the base steel material is further in any one of mass%, Mg: 0.0005-0.01%, Ca: 0.0005-0.01%, REM: 0.0005-0.01%. Or it is preferable to contain 2 or more types.

  In addition, the base steel material may be any one of Sn: 0.001 to 0.2%, Sb: 0.001 to 0.2%, and Se: 0.001 to 0.2% in mass%. Or it is preferable to contain 2 or more types.

  Further, the base steel material is further mass%, B: more than 0% and 0.01% or less, V: more than 0% and 0.1% or less, Zr: more than 0% and 0.1% or less, Zn: 0% It is preferable to contain any 1 type or 2 types or more of super 0.1% or less.

  According to the steel material for coating having excellent corrosion resistance according to the present invention, a steel structure in a severely corrosive environment such as a ship, an offshore structure, a bridge, etc., which is highly likely to corrode due to the influence of corrosive action such as seawater and flying sea salt particles. Even if it is used, it can exhibit good corrosion resistance.

  In steel materials with a coating on the surface, if the coating film formed on the surface is healthy, the corrosion inhibition effect of the steel material is large, and furthermore, a high anticorrosion effect can be obtained by selecting an appropriate coating system Are known. However, if any defects occur in the coating film or if wrinkles that expose the base steel material to the coating film occur, corrosion of the base steel material occurs starting from the coating film saddle, and further progresses. End up.

  The present inventor conducted research on a method of suppressing the occurrence of corrosion and further progress of the base steel material starting from such a coating ridge. As a result, in the paint film part, in addition to the corrosion reaction occurring at the exposed part of the base steel material, water and chloride ions and other corrosive factors enter the interface between the paint film and the base steel material. As a result, it was confirmed that corrosion under the coating film occurred inside the coating film, and it was found that these were greatly involved in the corrosion progress and expansion of the base steel material in the coating ridge.

  In addition, in steel materials with a coated surface, by forming a Zn-containing layer at the interface between the coating film and the base steel material, corrosion progression and coating film deterioration of the coating film heel may be caused by the sacrificial anticorrosive effect of Zn. It is well known that the corrosion resistance of coating is improved. From this point of view, in coating steel materials, a surface layer containing Zn may be formed on the base steel material by applying an inorganic zinc primer to improve corrosion resistance.

  The present inventor considered that the effect of the layer formed at the interface between the base steel material and the coating film is to suppress the corrosion progress and the coating film deterioration due to the sacrificial anticorrosive effect, but to further control the protection of the corrosion products. did. As a result, in the base steel material to which either one or two of Ti and Nb is added in addition to Cu and Cr, an appropriate amount of Cu is added to the surface in addition to Zn. In addition to the sacrificial anti-corrosion effect of Zn in the coating film ridge, the effect of improving the protection of the corrosion product can be obtained synergistically by forming the surface layer containing 1 type or 2 types. It has been found that the corrosion progress from the part can be remarkably suppressed and the corrosion resistance of the steel for coating can be greatly improved, and the present invention has been completed.

  Although it is known that the corrosion resistance is improved by adding Cu or Cr or the like to the base steel material, the corrosion resistance is improved in the present invention. In addition to the optimization of the coating layer, the layer provided at the interface between the coating film and the base steel material, that is, the surface layer formed on the surface of the base steel material is optimized to protect the corrosion products in the coating wall. The property is remarkably improved, and a corrosion resistance effect can be obtained.

  Hereinafter, the present invention will be described in detail based on embodiments. In addition to the base steel material and the surface layer constituting the steel material for painting of the present invention, the coating of the surface will be described in order.

<Component composition of base steel>
In addition to excellent corrosion resistance, the base steel material needs to satisfy mechanical properties and weldability required for a structural member. From these viewpoints, it is necessary to appropriately adjust the contents of Si, Mn, Al, P, and S in addition to the above-described Cu, Cr, Ti, and Nb. Hereinafter, the reasons for limiting the component ranges of these various additive elements will be described. All units are described as%, but indicate mass%.

・ C: 0.04 to 0.30%
C is a basic additive element necessary for securing the strength of the base steel material. In order to obtain the strength characteristics normally required as a base steel material, it is necessary to contain at least 0.04% or more. However, if C is excessively contained, the amount of cementite that acts as a cathode site in the acid solution increases, which accelerates the corrosion reaction and deteriorates the corrosion resistance. In addition, the toughness is also deteriorated. In order not to cause such an adverse effect due to excessive addition of C, the C content needs to be suppressed to 0.30% at most. Therefore, the content range of C is set to 0.04 to 0.30%. In addition, the minimum with preferable content of C is 0.045%, It is good to set it as 0.05% or more more preferably. Moreover, the upper limit with preferable content of C is 0.29%, It is good to set it as 0.28% or less more preferably.

・ Si: 0.05-1.0%
Si is also an element necessary for deoxidation and ensuring strength, and these effects cannot be obtained unless it is contained at least 0.05% or more. However, if the content exceeds 1.0%, weldability deteriorates. Therefore, the range of the Si content is set to 0.05 to 1.0%. In addition, the minimum with preferable content of Si is 0.08%, More preferably, it is good to set it as 0.10% or more. Moreover, the upper limit with preferable content of Si is 0.95%, More preferably, it is good to set it as 0.90% or less.

・ Mn: 0.1 to 2.5%
Like Si, Mn is an element necessary for deoxidation and securing strength, and if its content is less than 0.1%, the minimum strength as a steel material used as a structural member cannot be secured. However, if the content exceeds 2.5%, the toughness deteriorates. Therefore, the range of the Mn content is set to 0.1 to 2.5%. In addition, the minimum with preferable content of Mn is 0.15%, More preferably, it is good to set it as 0.2% or more. Moreover, the upper limit with preferable content of Mn is 2.4%, More preferably, it is good to set it as 2.3% or less.

-P: more than 0% and 0.04% or less P is an element that deteriorates toughness and weldability when excessively contained, and the upper limit of the allowable content of P is 0.04%. The content of P is preferably as small as possible, and the more preferable upper limit of the content of P is 0.038%, and more preferably 0.035% or less. However, it is difficult industrially to make P in the base steel material 0%.

S: more than 0% and 0.04% or less S is an element that deteriorates toughness and weldability when the content increases, and the upper limit of the allowable content is 0.04%. The upper limit with more preferable content of S is 0.038%, More preferably, it is good to set it as 0.035% or less. However, it is difficult to industrially make S in the base steel material 0%.

-Al: 0.005-0.20%
Al is also an element necessary for deoxidation and securing strength, like Si and Mn described above. In order to exhibit such an action effectively, it is necessary to contain 0.005% or more. However, if the content exceeds 0.20%, weldability is impaired, so the range of Al content is set to 0.005 to 0.20%. In addition, the minimum with preferable content of Al is 0.008%, More preferably, it is good to set it as 0.010% or more. Moreover, the upper limit with preferable content of Al is 0.19%, More preferably, it is good to set it as 0.18% or less.

Cu: 0.05 to 1.0%
Cu has a function of forming a dense rust film on the surface of the base steel material in addition to lowering the activity of the anode of the base steel material exposed portion in the coating film heel portion by dissolving in the ferrite solids. It is an element necessary for improving the corrosion resistance of the coat buttock. In order to exert such effects, it is necessary to contain at least 0.05% or more. However, if contained excessively, weldability and hot workability deteriorate, so the Cu content needs to be 1.0% or less. Therefore, the range of the Cu content is set to 0.05 to 1.0%. In addition, the minimum with preferable content of Cu is 0.06%, and a more preferable minimum is 0.07%. Moreover, the upper limit with preferable Cu content is 0.95%, and a more preferable upper limit is 0.90%.

・ Cr: 0.05-1.0%
Cr, as well as Cu, dissolves in ferrite and lowers the activity of the anode in the exposed portion of the base steel material in the coating ridge, and also has the effect of forming a dense rust film on the surface of the base steel material. It is an element necessary for improving the corrosion resistance of the buttock of the coating film. In order to exert such effects, it is necessary to contain at least 0.05% or more. However, since it will degrade weldability and hot workability if contained excessively, the Cr content needs to be 1.0% or less. Therefore, the Cr content range is set to 0.05 to 1.0%. In addition, the minimum with preferable Cr content is 0.06%, and a more preferable minimum is 0.07%. Moreover, the upper limit with preferable Cr content is 0.95%, and a more preferable upper limit is 0.90%.

・ N: 0.001 to 0.015%
N is an element that is effective in improving the corrosion resistance and securing the strength of the base steel material by forming finely dispersed particles of nitride in the steel. In order to obtain such an effect, the N content needs to be 0.001% or more. However, if the content is excessive, in addition to adversely affecting the toughness of the base steel material, the weldability is also impaired, so the upper limit of the N content is set to 0.015%. Therefore, the content range of N is set to 0.001 to 0.015%. In addition, the minimum with preferable content of N is 0.0015%, and 0.002% or more is more preferable. Moreover, the upper limit with preferable content of N is 0.014%, and 0.013% or less is more preferable.

-Ti: 0.005-0.1%, Nb: Any one or two of 0.005-0.1% Ti and Nb are dense on the surface of the base steel material in the presence of Cu and Cr. It has an action of forming a rust film and is an element necessary for improving corrosion resistance. In order to exhibit such an effect, it is necessary to contain at least 0.005% or more. However, since excessive weldability deteriorates weldability and hot workability, the contents of Ti and Nb must be 0.1% or less, respectively. The minimum with preferable content of Ti and Nb is 0.006%, respectively, and a more preferable minimum is 0.007%. Moreover, the upper limit with preferable content of Ti and Nb is 0.095%, respectively, and a more preferable upper limit is 0.09%.

  The above is the reason for limiting the component range of the essential additive elements of the base steel material constituting the steel material for painting of the present invention, and the balance is Fe and inevitable impurities. Inevitable impurities include O, H, and the like, and these elements may be contained to the extent that they do not impair the properties of the base steel material. However, by suppressing the total content of these inevitable impurities to 0.1% or less, preferably 0.09% or less, the corrosion resistance effect according to the present invention can be maximized.

  Further, it is more effective if the base steel constituting the steel for painting of the present invention contains the following elements. The reason for limiting the component range when these elements are contained will be described below.

Ni: 0.01-6.0%, Co: 0.01-5.0%, Mo: 0.01-2.0%, W: 0.01-2.0% 2 or more types Ni, Co, Mo, and W are effective elements for improving the corrosion resistance because they have a function of reducing the activity of the dissolution reaction by dissolving in ferrite. Appropriate amounts of Ni, Co, Mo, and W are effective for improving the strength characteristics of the base steel material, and are elements that are added as necessary. In order to exhibit such an effect, it is preferable to contain each 0.01% or more. However, if the content of these elements is excessive, weldability and hot workability are deteriorated. Therefore, when contained, Ni is 6.0% or less, Co is 5.0% or less, and Mo and W are 2. 0% or less. The more preferable lower limit when Ni, Co, Mo, and W are contained is 0.02%, more preferably 0.03% or more. Moreover, the upper limit with more preferable when Ni is contained is 5.9%, and it is still more preferable to set it as 5.8% or less. A more preferable upper limit when Co is contained is 4.9%, and more preferably 4.8% or less. The more preferable upper limit when Mo and W are contained is 1.9%, more preferably 1.8% or less.

-Mg: 0.0005-0.01%, Ca: 0.0005-0.01%, REM: Any one or more of 0.0005-0.01% Mg, Ca, REM is used In the environment, it has an effect of suppressing the pH drop near the surface of the steel material, and is an effective element for further improving the corrosion resistance. This effect is exhibited when these elements are dissolved by corrosion and react with hydrogen ions. In order to exhibit such an action effectively, it is preferable to contain 0.0005% or more of each. However, when the content of these elements is excessive, weldability and hot workability are deteriorated. Therefore, when these elements are contained, the content is set to 0.0005 to 0.01%. More preferable lower limits when Mg, Ca, and REM are contained are each 0.0006%, and further preferable lower limits are 0.0007%. On the other hand, a more preferable upper limit when containing Mg, Ca, and REM is 0.0095%, respectively, and a more preferable upper limit is 0.009%.

-Sn: 0.001-0.2%, Sb: 0.001-0.2%, Se: Any one or more of 0.001-0.2% Sn, Sb, Se is corrosion resistance Is an additive element effective in improving the resistance. The effect of improving the corrosion resistance is effectively exhibited by containing each of these elements in an amount of 0.001% or more. However, when the content of these elements is excessive, weldability and hot workability are deteriorated. Therefore, when these elements are contained, the content is 0.001 to 0.2%. The more preferable lower limit when Sn, Sb, and Se are contained is 0.002%, respectively, and the more preferable lower limit is 0.003%. On the other hand, a more preferable upper limit when Sn, Sb, and Se are contained is 0.19%, respectively, and a more preferable upper limit is 0.18%.

B: more than 0% and 0.01% or less, V: more than 0% and 0.1% or less, Zr: more than 0% and 0.1% or less, Zn: more than 0% and 0.1% or less, or Two or more elements, such as B, V, Zr and Zn, which are effective for improving the strength can be contained as required. Even if these additive elements are contained even in a very small amount, the effect of improving the strength is exhibited. Expressed in However, if these elements are contained excessively, the base material toughness and weldability deteriorate, so the content when these elements are contained is limited. When B is contained, the content is 0.01% or less, and when V, Zr, or Zn is contained, the content is 0.1% or less. A more preferable upper limit when B is contained is 0.0095%, and a further preferable upper limit is 0.009%. Moreover, a more preferable upper limit when V, Zr, and Zn are contained is 0.095%, and a more preferable upper limit is 0.09%.

<Structure of base steel>
The structure of the base steel material constituting the steel material for painting of the present invention is not particularly limited, but in order to obtain sufficient mechanical properties, it should be a structure composed of ferrite and pearlite, or a structure composed of ferrite and bainite. Is recommended.

<Manufacturing method of base steel>
In order to reliably manufacture the base steel material constituting the steel material for painting of the present invention, for example, it is preferable to manufacture the steel material by the method described below. First, for the molten steel that is discharged from the converter or electric furnace to the ladle, the RH vacuum degassing device is used to adjust the component composition specified in the present invention, and the temperature is adjusted for secondary refining. Do. Thereafter, the steel ingot may be formed by a normal casting method such as a continuous casting method or an ingot-making method. In order to ensure the basic properties such as mechanical properties and weldability required for steel materials as structural members, it is preferable to use killed steel as the deoxidation type, more preferably Al killed steel. Is done.

<Surface layer>
The steel material for coating of the present invention contains Zn: 20 to 200 g / m ² and Cu: 0.3 to 20.0 g / m ² on the surface of the base steel material, and further Cr: 0.3 to 20.0 g. / M ² , Ni: A surface layer containing any one or ^two of 0.3 to 20.0 g / m ² is applied.

Zn in the surface layer has an action of suppressing the progress of corrosion of the base steel material due to the sacrificial anticorrosive effect, and such an effect is exhibited when the Zn adhesion amount of the surface layer is 20 g / m ² or more. The minimum with more preferable Zn adhesion amount is 25 g / m < ² >, and 30 g / m < ² > or more is still more preferable. Further, when the Zn adhesion amount is increased to some extent, the sacrificial anticorrosive effect is not only saturated but also easily peeled off from the base steel material, so that the period during which the sacrificial anticorrosive action is effective may be shortened. From such a viewpoint, it is recommended that the Zn adhesion amount be 200 g / m ² or less. A more preferred upper limit of the Zn deposition amount is 190 g / ^{m 2,} more preferably 180 g / ^{m 2} or less.

  Moreover, when Cu and Cr, Cu and Ni, and Cu and Ni and Cr coexist in the surface layer containing the chemical component in the above-described content range, Since the rust is further refined and refined and the effect of inhibiting the entry of corrosion factors such as water and chloride ions into the rust layer is exerted, the corrosion reaction of the base steel material is suppressed, greatly improving the corrosion resistance. Contribute.

Such effects the deposition amount of Cu in the surface layer and 0.3 g / ^{m 2} or more, expressed by the inclusion further one or two of Cr and Ni 0.3 g / ^{m 2} or more. More preferable adhesion amounts of Cu, Cr and Ni on the surface layer are each 0.4 g / m ² or more, and more preferably 0.5 g / m ² or more. However, if the adhesion amount of Cu, Cr, and Ni is too large, the adhesion between the surface layer and the base steel material is reduced, and the surface layer is easily peeled off from the base steel material. In order to avoid such adverse effects, it is recommended that the adhesion amount of Cu, Cr and Ni be 20.0 g / m ² or less. More preferable upper limits of the adhesion amount of Cu, Cr and Ni are each 19.5 g / m ² or less, and more preferably 19.0 g / m ² or less.

  Examples of the method for forming this surface layer include mixing Zn powder, Cu powder, Cr powder and Ni powder with an appropriate solvent such as alkyl silicate, and spraying or brushing. Alternatively, a powder such as a Zn—Cu—Cr alloy, Zn—Cu—Ni alloy or Zn—Cu—Cr—Ni alloy having an appropriate composition may be prepared, and this alloy powder may be used in a normal primer coating process. . At this time, an appropriate pigment may be added as necessary. Alternatively, it is also possible to form the surface layer with Zn, Cu, Cr, and Ni as a desired deposition amount by using a thermal spraying method such as hot wire flame spraying or arc spraying. In addition, as a pretreatment for forming the surface layer, it is preferable to remove the scale and the like on the surface of the base steel material by shot blasting or the like.

  Moreover, in order to ensure the adhesion strength between the surface layer and the base steel material, it is preferable that the base steel surface has a surface roughness of a certain level or more. There is a concern that a portion where the layer and the base steel material do not adhere to each other is generated, and conversely the adhesion strength is lowered. From such a viewpoint, it is recommended that the surface of the base steel material has an appropriate surface roughness.

  As a specific surface roughness of the base steel material, for example, it is recommended that the 10-point average roughness Rzjis specified in JIS B 0601: 2001 be 10 μm to 80 μm. In addition, the adjustment of the surface roughness of the base steel material can be performed by adopting, for example, a normal shot blasting process or a grid blasting process.

<Paint>
The steel material for coating of the present invention is practically used by further coating the surface layer. As the paint used for painting, epoxy resin, chlorinated rubber, acrylic resin, fluororesin and urethane resin can be applied. It is also possible to do.

  For example, the paint for forming the epoxy resin coating film is not particularly limited as long as it is a paint used as an anticorrosion paint and contains an epoxy resin as a vehicle. Specific examples of the paint include an epoxy resin paint, a modified epoxy resin paint, and a tar epoxy resin paint.

  Moreover, as a coating material for forming the chlorinated rubber-based coating film, any coating material may be used as long as it is a coating material mainly composed of chlorinated resin, and is not particularly limited. Specific examples of the coating material include a coating material mainly composed of a chlorinated resin such as chlorinated rubber or chlorinated poroolefin.

  Examples of the paint for forming the acrylic resin coating film include ordinary acrylic resin paints, acrylic emulsion resin paints, acrylic urethane emulsion paints, acrylic silicon emulsion paints, and acrylic lacquers.

  Examples of the paint for forming the fluororesin coating film include paints such as tetrafluoroethylene resin paint, pearl fluoroalkoxy resin paint, and fluorinated ethylene propylene resin paint.

  Examples of the paint for forming the urethane resin coating film include paints such as polyurethane resin paint, polyester urethane resin paint, moisture-curing polyurethane resin paint, epoxy urethane paint, and modified epoxy urethane resin paint.

  If the film thickness is too thin, the anticorrosion effect will be insufficient, but conversely, if it is too thick, it tends to cause film peeling. . From such a viewpoint, it is recommended that the coating film thickness be a dry film thickness, for example, a thickness of 100 to 1000 μm.

Moreover, the coating process for forming the coating film is not particularly limited, and a normal coating method such as spray coating or brush coating can be applied. However, it is necessary to appropriately wash the surface of the base steel material to be coated before painting. For example, the adhesion salt concentration on the steel material surface by washing is 50 mg / m ² or less, preferably 10 mg / m ^{2 in} terms of NaCl. it is recommended to m ² or less.

  Examples of the form of the steel material for painting of the present invention include steel plates, steel pipes, steel bars, wire rods, and shaped steels. In addition, as an application, for example, it can be used as a structural member of a ballast tank in a ship such as a cargo ship such as a tanker, a container ship, a bulker, a cargo passenger ship, a passenger ship, a warship, etc. In addition, an upper deck, a bridge, a hatch cover, It can be used for various steel structures for ships such as cranes, various pipes, stairs and handrails.

In the case of offshore structures, wind power generation in the ocean, including structures that drill oil and gas on the ocean, floating facilities that produce, store, and ship oil and gas in the ocean, etc. , Power generation facilities such as wave power generation, tidal current / ocean current power generation, temperature difference power generation, and solar power generation. Moreover, in the bridge field, steel materials for bridges in a high flying salinity environment in which the flying salt amount exceeds approximately 0.1 mdd: mg / dm ² / day can be exemplified.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

[Production of test materials]
Steel materials having various component compositions shown in Table 1 were melted in a vacuum melting furnace to obtain a 50 kg steel ingot. The obtained steel ingot was heated to 1150 ° C. and then hot-rolled to obtain a steel material having a plate thickness of 10 mm. A test piece having a size of 150 mm × 70 mm × 5 mm was cut out from the steel material. Shot blasting is performed on one side of 150 mm x 70 mm, which is the test surface of all cut out test pieces, so that the 10-point average roughness Rzjis specified in JIS B 0601: 2001 is 30 ± 10 μm. The coating was performed after washing with water and acetone.

  A surface layer containing Zn, Cu, Cr, and Ni as appropriate was formed on one side having a size of 150 mm × 70 mm of the test piece subjected to the shot blast treatment. The surface layer was formed by spray-coating the test solution using a mixture of metal Zn, metal Cu, metal Cr and metal Ni appropriately mixed with alkyl silicate as a solvent. The adhesion amount of Zn, Cu, Cr and Ni on the surface layer was changed by appropriately adjusting the addition amount and application amount of Zn, Cu, Cr and Ni to the coating solution.

  The surface of 150 mm × 70 mm having the surface layer containing Zn, Cu or the like described above was applied by spraying a modified epoxy resin paint. The coating thickness is 200 ± 20 μm in terms of dry thickness. Furthermore, after the application surface of the modified epoxy resin coating was dried, a coating film was formed on the coated surface to reach a steel material base having a length of 80 mm and a width of 3 mm.

  All of the test pieces were subjected to the following corrosion test with the painted surface on which the wrinkles were formed as a test surface and the surfaces other than the test surface covered with a silicone sealant.

[Corrosion test method]
As a corrosion test simulating a corrosive environment by seawater, a combined cycle test using artificial seawater: CCT was performed. Cycle conditions are: 1) artificial seawater spray at 35 ° C., 1.5 hours, 2) temperature 60 ° C., relative humidity 20% RH, 2.5 hours, 3) temperature 50 ° C., relative humidity 95% RH, 2.5 Time was repeated.

  The transition time until the temperature and humidity during each process are changed and stabilized is 0.5 hours. The test period was 3 months. The sample is No. 1 shown in Table 2. 1 to No. Forty-nine 49 pieces were tested.

  As an evaluation of the degree of coating film deterioration and corrosion from the coating film buttock, the corrosion area and the corrosion depth from the coating film buttock of the test piece were determined after the CCT was completed. About the corrosion area, it was set as the total area of the area of the part which the coating film swells from the coating-film part by corrosion under a coating film, and the area of a coating-film part, and was taken as the average value of each three test pieces.

  About the corrosion depth, the corrosion depth of the coating film buttocks and its periphery was measured, and the maximum value of each three test pieces was calculated | required. The corrosion depth was measured after removing the coating film of the test piece after the end of CCT, performing derusting treatment by cathodic electrolysis in a 10% diammonium hydrogen citrate aqueous solution, and then measuring with a depth gauge. .

[Composite cycle test results]
Combined cycle test: Corrosion area and depth determined after CCT are as shown in Table 2. In addition, the corrosion area and the corrosion depth of each sample are No. 1 in which an ordinary Zn primer is formed on an ordinary steel material. The relative values when the corrosion area and the corrosion depth of one sample are 100 are shown.

  The evaluation criteria for the corrosion area and the corrosion depth are as follows. Corrosion area and corrosion depth are indicated by A when the relative value is 80 or more and less than 90, AA when the relative value is 70 or more and less than 80, and AAA when the relative value is less than 70. The corrosion depths of A to AAA were accepted in the overall evaluation, and the steel material for coating having excellent corrosion resistance was evaluated.

  No. 1-No. In No. 12, the relative value of the corrosion area and the corrosion depth is 90 to 100, and the corrosion resistance of the coating ridge is not sufficient. No. 2, no. 6 and no. No. 7 contains Zn, Cu, and Cr as defined in the present invention in the surface layer, but since the Cu content of the steel material is too small, the corrosion resistance of the coating film cannot be sufficiently improved.

  No. 3 and no. No. 8 contains Zn, Cu, and Cr as defined in the present invention in the surface layer. However, since the Cr content of the base steel material is too small, the corrosion resistance of the coating film ridge cannot be sufficiently improved.

  No. 4 and no. No. 5 contains Zn, Cu, Cr as defined in the present invention in the surface layer, but since the Ti content or Nb content of the base steel material is too small, sufficient improvement in the corrosion resistance of the coating ridge is obtained. Absent.

  No. 9 and no. In all cases, the component composition of the base steel material satisfies the provisions of the present invention, but since the surface layer contains too little Zn or Cu, the corrosion resistance of the coating film ridge cannot be sufficiently improved.

  No. 11 and no. No. 12 is a component composition of the base steel material and Zn and Cu of the surface layer satisfy the provisions of the present invention, but since both of them have too little Cr or Ni in the surface layer, the corrosion resistance of the coating film ridge cannot be sufficiently improved. .

  For these comparative examples, No. 1 satisfying all the rules of the present invention. 13-No. In each of the 49 samples, both of the relative values of the corrosion area and the corrosion depth are suppressed to less than 90, and the excellent corrosion resistance of the paint film buttock is exhibited.

  In particular, No. 1 in which a surface layer defined in the present invention was formed on a base steel material of S12 to S18 containing an appropriate amount of any one or more of Ni, Co, Mo and W. 18-No. The sample No. 27 has a remarkable effect of suppressing the corrosion area.

  No. 1 in which the surface layer defined by the present invention was added to the base steel materials of S28 and S29, in which any one or more of Sn, Sb and Se were further contained. 40-No. In the sample of 42, the effect of suppressing the corrosion area is further remarkable.

  Moreover, No. 1 which provided the surface layer prescribed | regulated to this invention to the base steel material of S19-S21 which contained any 1 type or 2 types or more of Mg, Ca, and REM appropriately. 28-No. The sample 31 has a remarkable effect of suppressing the corrosion depth.

  No. 1 in which a surface layer defined by the present invention was added to a base steel material of S30 to S32 in which an appropriate amount of any one or more of Sn, Sb and Se was further added. 43-No. In the 46 samples, the effect of suppressing the corrosion depth is more remarkable.

  As described above, all of the coating steel materials of the present invention exhibit excellent corrosion resistance of the coating ridge in a seawater environment, and are suitable as a structural member that is exposed to seawater and flying sea salt particles. .

Claims (5)

A steel material for coating including a base steel material and a surface layer formed on the surface of the base steel material,
The base steel material is mass%, C: 0.04 to 0.30%, Si: 0.05 to 1.0%, Mn: 0.1 to 2.5%, P: more than 0% 0.04 %: S: more than 0% and 0.04% or less, Al: 0.005 to 0.20%, Cu: 0.05 to 1.0%, Cr: 0.05 to 1.0%, N: 0 0.001 to 0.015%, Ti: 0.005 to 0.1%, Nb: 0.005 to 0.1%, one or two of them, the balance being Fe and inevitable Steel made of mechanical impurities,
Moreover, while the said surface layer contains Zn: 20-200g / m < ² >, Cu: 0.3-20.0g / m < ² >, Cr: 0.3-20.0g / m < ² >, Ni: 0. A steel material for coating excellent in corrosion resistance, comprising any one or ^two of 3 to 20.0 g / m ² .   The base steel material is further, in mass%, Ni: 0.01 to 6.0%, Co: 0.01 to 5.0%, Mo: 0.01 to 2.0%, W: 0.01 to The steel material for coating excellent in corrosion resistance according to claim 1, which contains any one or more of 2.0%.   Further, the base steel material may be any one of Mg: 0.0005 to 0.01%, Ca: 0.0005 to 0.01%, REM: 0.0005 to 0.01%, or 2% by mass. The steel material for coating excellent in corrosion resistance according to claim 1 or 2 containing a seed or more.   Further, the base steel material may be any one of Sn: 0.001 to 0.2%, Sb: 0.001 to 0.2%, Se: 0.001 to 0.2%, or 2% by mass. The steel material for coating excellent in corrosion resistance according to any one of claims 1 to 3, comprising at least a seed.   The base steel material is further in mass%, B: more than 0% to 0.01% or less, V: more than 0% to 0.1% or less, Zr: more than 0% to 0.1% or less, Zn: more than 0% to 0% The steel material for coating excellent in corrosion resistance according to any one of claims 1 to 4, which contains any one or more of 1% or less.