JP6515282B2 - Corrosion resistant steel for acidic environment and method for preventing corrosion - Google Patents

Description

  The present invention relates to a corrosion resistant steel material for use in an acidic corrosive environment and a method for preventing corrosion.

  In the flue gas system of coal-fired power boilers and waste incineration facilities, high concentrations of sulfuric acid and hydrochloric acid are generated due to sulfur trioxide and hydrogen chloride contained in the combustion gas. In such an environment, corrosion by a strong acid, such as sulfuric acid dew point corrosion and hydrochloric acid dew point corrosion, becomes a problem. And in order to suppress corrosion by strong acid whose pH is less than 2, the steel materials excellent in acid-proof dew point corrosion resistance which added Cu, Sb, etc. are proposed (for example, refer to patent documents 1 and 2).

  Also, in general, steel materials used in severe corrosive environments are coated on the surface to shield them from various corrosion factors. However, when the coating reaches a damage due to deterioration of the coating, etc., the effect of the corrosion protection is lost and local corrosion progresses rapidly. To prevent corrosion caused by chloride, which is a problem in such a beach area or an area where an antifreeze agent is applied, a coating film containing a substance using Sn ions as a supply source is formed on the steel surface A method has been proposed (see, for example, Patent Documents 3 to 5).

JP 2001-164335 A Unexamined-Japanese-Patent No. 2003-233367 JP, 2006-315238, A JP, 2006-316139, A JP 2007-230088 A

  Steels (acid-resistant dew-point corroded steels) with excellent acid dew-point corrosion resistance to which conventional Cu, Sb, etc. have been added are used as bare materials without coating etc. in exhaust gas chimneys of boilers and incineration facilities. Demonstrates excellent corrosion resistance against dew point corrosion that occurs in less than a strong acid environment. However, when used as a bare material, conventional acid-resistant dewpoint-corrosed steels do not predominate dew point corrosion in an acidic environment with a pH of 2 or more, particularly in a weakly acidic environment with a pH of 2 to 4, compared with ordinary steels and stainless steels There is no big difference in corrosion resistance. Rather, stainless steel has sometimes been superior in corrosion resistance.

  In view of such circumstances, the present invention exhibits excellent corrosion resistance not only in a strong acid environment having a pH of less than 2 such as high concentration sulfuric acid or hydrochloric acid but also in a weak acid environment having a pH of 2 to 4, strongly acidic environment It is an object of the present invention to provide a corrosion resistant steel material for an acidic environment which can be used in a wide range of acidic environments from weak acid environments to a weakly acidic environment, and a corrosion protection method for coating the corrosion resistant steel material.

  The inventors of the present invention, when considering the problem to be solved, in an environment where corrosion due to chloride is a problem, steel coated with Sn ions is used as the base steel material in the coating ridge portion or the coating fragile portion. We focused on the fact that even if exposed, the progress of corrosion in the vicinity was suppressed. Therefore, the effects of the addition of alloy components such as Cu, Sb, and Sn, the coating containing Sn ions, and various other coatings on the corrosion resistance of steel materials in a weakly acidic environment of pH 2 to 4 were examined. As a result, in the corrosion resistant steel coated with the Sn-containing layer, the progress of corrosion is limited to the coating ridge portion or the coating fragile portion, but Cu and Sb which are eluted from the steel in the coating ridge portion or fragile portion It has been found that the synergetic effect with the Sn ions eluted from the Sn-containing layer significantly improves the corrosion resistance in an acidic environment. That is, the combination of a steel material simultaneously added with Cu and Sb and a coating containing Sn ions causes dew point corrosion by Cu and Sb to be exhibited in a strong acid environment with a pH of less than 2, and Sn in a weakly acidic environment with a pH of 2 to 4 We found that the synergetic effect of Cu, Cu, and Sb develops corrosion resistance, and it can be widely used in strongly acidic environments to weakly acidic environments.

The present invention has been made based on such findings, and the summary thereof is as follows.
[1] in mass%,
C: 0.001 to 0.20%,
Si: 0.01 to 2.50%,
Mn: 0.10 to 2.00%,
Cu: 0.10 to 1.00%,
Sb: 0.01 to 0.20%
Contains
P: 0.05% or less,
S: A steel material limited to 0.05% or less and the balance being Fe and unavoidable impurities,
It has a Sn-containing layer containing a Sn ion supplying substance and a binder on the surface of the steel material or on the rust layer formed on the surface of the steel material,
The corrosion resistant steel material for an acidic environment, wherein the amount of the Sn ion supplying substance is 1 to 54 mass% in terms of metal Sn based on the total solid content mass of the Sn-containing layer.
[2] The above-mentioned steel material is further in mass%,
Mo: 1.00% or less,
W: 1.00% or less,
Ni: 1.00% or less,
Sn: The corrosion resistant steel material for acidic environment as described in the above [1], which contains one or two or more of 0.50% or less.
[3] The above-mentioned steel material is further in mass%,
Cr: 0.50% or less,
Ti: 0.150% or less,
Nb: 0.150% or less,
V: 0.50% or less,
Ta: 0.040% or less,
B: The corrosion resistant steel material for acidic environment as described in the above [1] or [2], which contains one or more of 0.010% or less.
[4] The above-mentioned steel material is further in mass%,
Al: 0.10% or less,
Ca: 0.010% or less,
Mg: 0.010% or less,
REM: The corrosion resistant steel material for an acidic environment according to any one of the above [1] to [3], which contains one or more of 0.010% or less.
[5] The Sn-containing layer further contains one or more metal ion supply substances supplying one or more of Cu ²⁺ ion, Ni ²⁺ ion, Cr ³⁺ ion, and the Sn ion supply substance The total amount of the metal ion supplying substance is 65% or less of the total amount of metal Sn, metal Cu, metal Ni, and metal Cr with respect to the total solid mass of the Sn-containing layer. The corrosion resistant steel material for an acidic environment according to any one of the above [1] to [4], which is characterized by the above.
[6] The corrosion resistant steel material for acidic environment according to any one of the above [1] to [5], further comprising an organic resin layer having a thickness of 10 to 100 μm on the Sn-containing layer. .
[7] The corrosion resistant steel material for an acidic environment according to any one of [1] to [6], wherein the Sn-containing layer has a thickness of 5 to 50 μm.
[8] mass%,
C: 0.001 to 0.20%,
Si: 0.01 to 2.50%,
Mn: 0.10 to 2.00%,
Cu: 0.10 to 1.00%,
Sb: 0.01 to 0.20%
Contains
P: 0.05% or less,
S: 0.05% or less limited, prepare the steel material whose remainder is Fe and unavoidable impurities,
The Sn ion supplying material is mixed with a binder to prepare a Sn-containing paint so that the Sn-containing paint is prepared on the surface of the steel material so that the amount of the metal Sn is 1 to 54% by mass in terms of metal Sn Alternatively, it is applied on a rust layer formed on the surface of the steel material to form a Sn-containing layer.
[9] The above-mentioned steel material is further in mass%,
Mo: 1.00% or less,
W: 1.00% or less,
Ni: 1.00% or less,
Sn: One or more 0.50% or less of the anticorrosion method described in the above [8] characterized by containing one or more.
[10] The above-mentioned steel material is further in mass%,
Cr: 0.50% or less,
Ti: 0.150% or less,
Nb: 0.150% or less,
V: 0.50% or less,
Ta: 0.040% or less,
B: The anticorrosion method according to the above [8] or [9], which contains one or more of 0.010% or less.
[11] The above-mentioned steel material is further in mass%,
Al: 0.10% or less,
Ca: 0.010% or less,
Mg: 0.010% or less,
REM: The anticorrosion method according to any one of the above [8] to [10], containing one or more of 0.010% or less.
[12] The metal ion supplying substance is mixed with the binder so that the total of the Sn converted amount, the Cu converted amount, the Ni converted amount, and the Cr converted amount is 65% or less with respect to the total solid mass. The anticorrosion method according to any one of the above [8] to [11], which comprises preparing a containing paint.
[13] The anticorrosion method according to any one of the above [8] to [12], further comprising forming an organic resin layer having a thickness of 10 to 100 μm on the Sn-containing layer.
[14] The anticorrosion method according to any one of the above [8] to [13], wherein the Sn-containing layer is formed to a thickness of 5 to 50 μm.

  According to the present invention, not only a strong acid environment having a pH of less than 2 such as high concentration sulfuric acid or hydrochloric acid but also an acid environment including a weak acid environment having a pH of 2 to 4 exhibits excellent corrosion resistance, It is possible to provide a corrosion resistant steel for acid environment, which suppresses the progress of local corrosion in a coating part or a coating weak part, and a corrosion prevention method for applying a coating to the corrosion resistant steel, It is.

  The corrosion resistant steel material for acidic environment of the present invention is characterized in that a coating containing Sn ions is applied on a steel plate simultaneously containing Cu and Sb, and its corrosion resistance is improved by the conventional acid dew point corrosion steels and the conventional Sn ion containing It is not in paint.

  About the reason for which the corrosion resistant steel materials for acidic environments of this invention express the above-mentioned outstanding corrosion resistance, the present inventors estimate as follows.

  In the case of the bare material which is not coated, the corrosion resistance of the corrosion resistant steel material to which Cu and Sb are simultaneously added is significantly improved in a strong acid environment of pH less than 2 as compared to that of ordinary steel, but at pH 2 or more ordinary steel It can not be said that it improves significantly compared to. This is because the corrosion rate of the steel material is high in a strong acid environment and the elution amount of the alloy components contained in the steel is large, so the effect of improving the corrosion resistance by Cu and Sb is remarkably exhibited, but the pH is 2 or more It is considered that this is because the corrosion rate of the steel material decreases and the elution amount of alloy components decreases.

  On the other hand, in the case of a coated steel material, corrosion progresses locally at a limited site such as a coating ridge portion or a coating fragile portion (e.g., a portion where the coating film is thin). That is, the coating ridge portion becomes an anode and the coating portion becomes a cathode, and as the corrosion progresses, the coating film is peeled off to generate a new anode site. The local corrosion of the coated steel material proceeds faster than the general corrosion of the bare material, and the elution amount of the alloy component contained in the steel at the coating ridge portion or the coating fragile portion also increases. Therefore, if the steel material under the coating film contains a corrosion resistant component, it is considered that the effect of suppressing the progress of corrosion by the component will be exhibited.

  Therefore, in the case of a coated steel material, by including both Cu and Sb in the steel material, the amount of elution of the alloy component is increased in the coating corroded portion and the coating fragile portion corroded locally, and thus locally It is considered that the eluted alloy components effectively act on the progress of corrosion. And if corrosion advances to a certain extent, the elution amount of Sn ion contained in the paint will also increase, and it will contribute to suppression of dissolution of the steel material at the anode, and the corrosion resistance improvement in the above-mentioned coating ridge or coating fragile portion It is thought that it will contribute to

  However, when the coating film which does not contain Sn ion is formed in the steel material simultaneously containing Cu, Sb, and Sn, the inventor found that the same effect as the corrosion resistant steel material for acidic environment of the present invention can not be obtained. . Further, when a coating film containing Sb ions is formed on a steel material simultaneously containing Cu and Sn but not containing Sb, the same effect as the corrosion resistant steel material for acidic environment of the present invention can not be obtained. Therefore, in the present invention, it is necessary to apply a coating containing Sn ions on a steel plate simultaneously containing Cu and Sb.

  Hereinafter, the present invention will be described in detail.

  First, the reason for limiting the components of the steel material will be described. The notation of% means mass% unless otherwise noted.

(C: 0.001 to 0.20%)
C is an element to improve the strength, and it is necessary to contain 0.001% or more. Preferably, the amount of C is 0.01% or more. On the other hand, when the amount of C exceeds 0.20%, the corrosion resistance deteriorates, so the amount of C is made 0.20% or less. Preferably, the amount of C is 0.10% or less, more preferably 0.05% or less.

(Si: 0.01 to 2.50%)
Si is an element which contributes to deoxidation and improvement of strength, and it is necessary to contain 0.01% or more. Preferably, the amount of Si is 0.05% or more. On the other hand, since the inclusion of Si exceeding 2.50% causes adhesion of the hot rolling scale and a decrease in toughness, the amount of Si is limited to 2.50% or less. Preferably, the amount of Si is 1.00% or less, more preferably 0.50% or less.

(Mn: 0.10 to 2.00%)
Mn is an element that improves strength and toughness, and 0.10% or more is added. Preferably, the Mn content is 0.20% or more, more preferably 0.50% or more. On the other hand, when 2.0% or more of Mn is added, coarse MnS is generated and the corrosion resistance and mechanical properties deteriorate, so the amount of Mn is made 2.0% or less. Preferably, the Mn content is 1.50% or less, more preferably 1.20% or less.

(Cu: 0.10 to 1.00%)
Cu is a very important element which exhibits remarkable corrosion resistance to sulfuric acid and hydrochloric acid when added simultaneously with Sb. In order to secure corrosion resistance in an acidic environment, it is necessary to make the amount of Cu 0.10% or more. Preferably, the amount of Cu is 0.20% or more. On the other hand, when Cu is added in excess of 1.00%, the productivity is reduced, so the amount of Cu is made 1.00% or less. Preferably, the Cu content is 0.70% or less, more preferably 0.40% or less.

(Sb: 0.01 to 0.20%)
As mentioned above, Sb is an important element in the present invention, and in order to ensure corrosion resistance in an acidic environment, it is necessary to add 0.01% or more. Preferably, the amount of Sb is 0.05% or more, more preferably 0.10% or more. On the other hand, when Sb exceeding 0.20% is added, the hot workability and the toughness decrease, so the Sb amount is made 0.20% or less. Preferably, the amount of Sb is made 0.15% or less.

(P: 0.05% or less)
P is an impurity and limits the amount of P to 0.05% or less in order to reduce the mechanical properties and the manufacturability of the steel material. Preferably, the P amount is 0.020% or less. The lower limit of the amount of P is not limited and may be 0%, but it is preferable to be 0.001% or more from the viewpoint of cost.

(S: 0.05% or less)
S is an impurity, and the amount of S is limited to 0.05 or less in order to reduce the hot workability and the mechanical properties of the steel material. On the other hand, since S improves the corrosion resistance in an acidic environment when it is simultaneously contained with Cu and Sb, 0.001% or more may be contained. More preferably, the amount of S is 0.005% or more, more preferably 0.01% or more.

  Furthermore, in order to improve corrosion resistance in an acidic environment, one or more of Mo, W, Ni, and Sn can be contained.

(Mo: 1.00% or less)
Mo is an element that improves the corrosion resistance in an acidic environment by adding simultaneously with Cu and Sb. The amount of Mo is preferably 0.01% or more, more preferably 0.10% or more. On the other hand, since Mo is an expensive element, the amount of Mo is preferably 1.00% or less, more preferably 0.50% or less from the viewpoint of cost.

(W: 1.00% or less)
W is an element that improves the corrosion resistance in an acidic environment, and may contain 0.01% or more. More preferably, the W amount is 0.10% or more. On the other hand, since W is also an expensive element, the amount of W is preferably 1.00% or less, more preferably 0.50% or less from the viewpoint of cost.

(Ni: 1.00% or less)
Ni is an element that improves the corrosion resistance in an acidic environment, and when Cu is contained as in the corrosion resistant steel material for an acidic environment of the present invention, it exhibits an effect of enhancing the productivity. Preferably, the amount of Ni is 0.01% or more, more preferably 0.05% or more, and further preferably 0.10% or more. On the other hand, since Ni is also an expensive element, the amount of Ni is preferably 1.00% or less, more preferably 0.50% or less from the viewpoint of cost.

(Sn: 0.50% or less)
Although the effect is not remarkable as compared with Sb, Sn is an element that improves the corrosion resistance in an acidic environment, and may contain 0.01% or more. The amount of Sn is more preferably 0.02% or more, and still more preferably 0.05% or more. On the other hand, since hot workability and toughness will fall when Sn is contained excessively, 0.50% or less of the amount of Sn is preferred. More preferably, the amount of Sn is 0.30% or less.

  Furthermore, in order to improve mechanical properties and the like, one or more of Cr, Ti, V, Nb, Ta, and B can be contained.

(Cr: 0.50% or less)
Cr is an element that enhances the hardenability and improves the strength, and may contain 0.01% or more. More preferably, the amount of Cr is 0.05% or more. Further, Cr is an element that enhances the weather resistance, but it may lower the corrosion resistance in an acidic environment, and the Cr amount is preferably 0.50% or less. More preferably, the Cr content is 0.30% or less, more preferably 0.10% or less.

(Ti: 0.150% or less)
Ti is an element that forms a nitride and contributes to the refinement of crystal grains and the improvement of the strength, and the amount of Ti is preferably 0.005% or more. More preferably, the amount of Ti is made 0.010% or more. On the other hand, the addition of Ti over 0.150% may deteriorate mechanical properties, so the upper limit of the Ti amount is preferably 0.150% or less. The more preferable upper limit of the amount of Ti is 0.10% or less, and more preferably 0.050% or less.

(Nb: 0.150% or less)
Nb is an element which forms a nitride like Ti, and may contain 0.001% or more for the purpose of refinement of crystal grains and improvement of strength. More preferably, the amount of Nb is made 0.005% or more. On the other hand, since the mechanical properties may deteriorate if Nb exceeding 0.150% is added, the upper limit of the Nb amount is preferably 0.150% or less. A more preferable upper limit of the Nb amount is 0.10% or less, and more preferably 0.050% or less.

(V: 0.50% or less)
V, like Ti and Nb, is an element that forms a nitride, but can be added mainly to improve the strength by precipitation strengthening. In order to acquire an effect, it is preferable to make V amount into 0.005% or more. More preferably, the V amount is 0.010% or more. On the other hand, when V of more than 0.50% is added, the mechanical properties may deteriorate, so the upper limit of the amount of V is preferably 0.50% or less. A more preferable upper limit of the amount of V is 0.20% or less, and more preferably 0.30% or less.

(Ta: 0.040% or less)
Ta is an element that contributes to the improvement of the strength, and may contain 0.001% or more. Although the mechanism is not necessarily clear, Ta also contributes to the improvement of the corrosion resistance, and more preferably, the amount of Ta is made 0.005% or more. On the other hand, if the content of Ta is excessive, the cost increases, so the amount of Ta is preferably 0.040% or less. More preferably, the amount of Ta is made 0.020% or less.

(B: 0.010% or less)
B is an element that enhances hardenability and improves strength, and may contain 0.0001% or more. More preferably, the B content is made 0.0003% or more, more preferably 0.0005% or more. On the other hand, when B of more than 0.010% is added, the mechanical properties may deteriorate, so the upper limit of the amount of B is preferably 0.010% or less. A more preferable upper limit of the amount of B is 0.005% or less, and more preferably 0.003% or less.

  Furthermore, for the purpose of deoxidation and control of inclusions, one or more of Al, Ca, Mg and REM can be contained.

(Al: 0.10% or less)
Al is a deoxidizing agent, and preferably contains 0.005% or more, more preferably 0.01% or more, and still more preferably 0.02% or more. On the other hand, if Al is excessively contained, ductility and hot workability may be impaired due to an increase in inclusions, so the Al content is preferably made 0.10% or less. More preferably, the amount of Al is 0.05% or less, more preferably 0.03% or less.

(Ca: 0.010% or less, Mg: 0.010% or less, REM: 0.010% or less)
Ca, Mg, and rare earth elements (REM) are elements used to control oxides and sulfides, and each may contain 0.0005% or more. If any of Ca, Mg and rare earth elements (REM) is added in excess of 0.010%, the mechanical properties may be impaired, so the upper limit is preferably 0.010% or less. More preferably, the upper limit is made 0.005% or less.

  In the present invention, the balance other than the above elements consists of Fe and unavoidable impurities, but other elements can be added in a small amount within the range not to impair the effects of the present invention.

  The shape of the corrosion resistant steel material of the present invention is not particularly limited, and may be a steel plate, a steel strip, a shaped steel, a steel pipe, a steel bar, a steel wire, or the like. Although the thickness of steel materials, such as a steel plate, a steel strip, a shape steel, and a steel pipe, is not specifically limited, Usually, it is 3-50 mm. The preferred lower limit is 6 mm, more preferably 10 mm, and the preferred upper limit is 40 mm, more preferably 30 mm.

Next, the Sn-containing layer will be described. An Sn-containing layer including an Sn ion supplying substance and a binder is formed directly on the surface of the corrosion resistant steel material having the above-described component composition or on a rust layer formed on the surface of the corrosion resistant steel material. "Sn ion supply material" means a material which can be dissolved in an acidic solution to supply one or both of Sn ²⁺ ions and Sn ⁴⁺ ions. Such Sn ion supply materials specifically include divalent Sn compounds, tetravalent Sn compounds, and further metal Sn.

  In the corrosion resistant steel coated with the Sn-containing layer, the progress of corrosion is limited to the coating ridge portion, the coating fragile portion, and the like. And it is thought that the corrosion resistance in an acidic environment is remarkably improved by the synergetic effect of Cu and Sb eluted from the steel and Sn ions eluted from the Sn-containing layer.

  In order to express such an effect, the amount of the Sn ion supplying material needs to be 1% by mass or more in terms of metal Sn with respect to the total solid content mass of the Sn-containing layer. Preferably, it is 2% by mass or more. On the other hand, when the amount of the Sn ion supplying substance exceeds 54% by mass in terms of metal Sn based on the total solid content mass of the Sn-containing layer, a binder having adhesiveness to fix the Sn ion supplying substance is used. The amount of the binder is relatively short, and the adhesion of the Sn-containing layer is reduced. Therefore, the upper limit of the amount of the Sn ion supply material is set to 54% by mass or less. Preferably, it is 40% by mass or less. The term “total solid mass” means the mass excluding the solvent used to disperse the Sn ion supplying substance and / or the metal ion supplying substance described later in the binder, or drying at a temperature at which the binder does not thermally decompose. The mass of the Sn-containing layer after being allowed to

When the Sn ion supply substance is a Sn compound, the amount of metal Sn can be calculated according to the following equation.
(Mass of Sn compound) × [(Sn atomic weight) / (molecular weight of Sn compound)] (formula 1)

The feed material of Sn ^ions may be at least one of acid-soluble divalent Sn compounds or tetravalent Sn compounds that generate Sn ²⁺ or Sn ⁴⁺ ions, and metal Sn. Preferably it is a bivalent compound. As specific examples of the divalent compound, tin (II) sulfate, tin (II) oxide and tin (II) pyrophosphate can be mentioned. Tin (II) sulfate is a particularly preferred source of Sn ions for use in the present invention, as it is difficult to dissolve in the neutral region and dissolves in the low PH region.

In the binder, in addition to the Sn ion source, it is also possible to coexist a metal ion supplying substance as a source of metal cations for improving the corrosion resistance, such as Cu ²⁺ , Ni ²⁺ and Cr ³⁺ ions. An acid-soluble metal compound or metal may also be used for this metal ion supply material. For example, Cu (NO ₃ ) ₂ , CuSO ₄ , Ni (NO ₃ ) ₂ , NiSO ₄ , Cr (NO ₃ ) ₃ , Cr ₂ (SO ₄ ) ₃ or the like.

  These additional metal ion supplying materials can be used one or more kinds in order to improve the corrosion resistance. The metal ion supplying materials can be added in total amount in terms of metal relative to the total solid content of the Sn-containing layer It is preferable to add to a binder so that it will be 1 mass% or more. The upper limit is preferably 20% by mass or less. Moreover, it is preferable to add to a binder so that a total amount with a Sn ion supply substance may be 65 mass% or less in metal conversion amount with respect to the total solid of a Sn content layer.

When the metal ion supplying substance is an M compound (M is one of Cu, Ni, and Cr), the mass in terms of metal is the same as the following formula, similarly to the metal Sn converting amount when the Sn ion supplying substance is a Sn compound: It can be calculated according to
(M mass of M compound) × [(M atomic weight) / (molecular weight of M compound)] (formula 2)

  Although the said binder in particular is not restrict | limited, It is preferable that it is resin and can use various organic resin used for paints. Resin used as a binder is called binder resin. Specifically, epoxy resin, urethane resin, vinyl resin, polyester resin, acrylic resin, alkyd resin, phthalic acid resin, butyral resin, melamine resin, phenol resin and the like can be mentioned. These may be in the form of either a solution or an emulsion. From the viewpoint of securing the strength of the Sn-containing layer, the amount of the binder as the solid content is preferably 25% by mass or more, and more preferably 30% by mass or more, based on the total solid content of the Sn-containing layer.

  The thickness of the Sn-containing layer is required to be 5 μm or more in order to improve the corrosion resistance in an acidic environment by supplying Sn ions to the coating ridge portion or the coating fragile portion. Preferably, it is 10 μm or more, more preferably 20 μm or more. The upper limit of the thickness of the Sn-containing layer is preferably as large as possible from the viewpoint of corrosion resistance, but is set to 50 μm or less from the viewpoint of coating workability and the like.

  In order to improve the durability, an organic resin layer having a thickness of 10 μm or more may be further formed on the Sn-containing layer. The upper limit of the thickness is preferably as thick as possible from the viewpoint of durability, but is preferably 100 μm or less from the viewpoint of coating workability and the like. The upper limit is more preferably 50 μm or less.

  The organic resin layer is not particularly limited, but for example, paints such as epoxy resin, urethane resin, vinyl resin, polyester resin, acrylic resin, alkyd resin, phthalic acid resin, butyral resin, melamine resin, phenol resin, etc. form an organic resin layer It can be used for In addition, color pigments such as bengara, titanium dioxide, carbon black and the like, and extender pigments such as talc, silica, mica and the like can be added alone or in combination.

  Next, the manufacturing method of the corrosion resistant steel material for acidic environments of this invention is demonstrated. An Sn-containing layer containing an Sn ion supplying substance and a binder on the surface of the corrosion resistant steel material having the above-mentioned components produced by the conventional method or on the rust formed on the surface of the corrosion resistant steel material Is formed such that it is 1 to 54% by mass in terms of metal Sn based on the total solid content mass of the Sn-containing layer. As such a formation method, the Sn-containing coating may be applied and dried by a conventional method to form a Sn-containing layer, using a Sn ion supplying substance and a binder.

  The corrosion-resistant steel before forming the Sn-containing layer is, for example, a molten steel made by a known method such as a converter or an electric furnace, and a steel such as slab or billet by a known method such as a continuous casting method or an ingot method. The material may be manufactured by hot rolling. The molten steel may be subjected to processing such as ladle refining or vacuum degassing. The steel material after casting or forging may be hot-rolled as it is. Furthermore, after hot rolling, heat treatment and cold working can be performed.

  The method for forming the Sn-containing layer is not particularly limited. For example, the above-described Sn ion supplying substance and metal ion supplying substance are put in a paint, dispersed by a dissolver or a ball mill, etc. to prepare a Sn-containing paint, and the Sn-containing paint is on the surface of the steel or You may form the said Sn containing layer by apply | coating on the rust layer formed in the surface of steel materials, and drying.

  Alternatively, the binder described above, the Sn ion supplying material and the metal ion supplying material described above are uniformly mixed to prepare a Sn-containing paint, and the Sn-containing paint is on the surface of the steel or the surface of the steel Alternatively, the Sn-containing layer may be formed by coating on a rust layer formed on the surface. The Sn-containing paint uniformly mixes the binder and the solvent, or dissolves the binder in the solvent to prepare a solution, and then uniformly disperses the Sn ion supply material and the metal ion supply material in the solution. It may be manufactured by. The composition of the Sn-containing paint is the mass of the solid content of the binder relative to the total mass of the solid content mass of the binder and the solid content mass of the Sn ion-supplying substance and the metal ion-supplying substance It is necessary to adjust the solid content mass of the feed material and the metal ion supply material to be the predetermined ratio described above.

  Coating using a Sn-containing paint containing a Sn ion supplying substance and a binder can be performed according to a conventional method. For example, in the case of existing structures, methods such as air spray, airless spray, brushing and the like are suitable. In the case of painting in a factory, other methods such as roll coating and immersion may be employed. The solvent is preferably evaporated by natural drying after coating, and such solvent is preferably used. The coating is performed such that a Sn-containing layer having a thickness of 5 to 50 μm is formed after drying. Also when forming an organic resin layer on a Sn content layer, it may carry out by a conventional method similarly.

  A steel having the composition shown in Table 1 was melted and cast, and the obtained steel slab was heated to 1100 ° C., hot rolled to a thickness of 5 mm with a finishing temperature of 740 ° C., and air cooled to room temperature. Steel No. 1 was obtained as a test piece of length 150 mm, width 60 mm, and thickness 4 mm from the obtained steel plate. 1 to 14 were collected. The surface of the test piece was subjected to a blasting treatment to be Sa 2.5 (ISO 8501-1) or higher.

  An epoxy resin containing tin (II) sulfate, which was unpainted or a source of Sn ions, was applied to the test specimen after blasting to form a Sn-containing layer. An epoxy resin containing no Sn ion and an epoxy resin containing an Sb ion source instead of the Sn ion source were applied to some test pieces to form a coating. The fluorocarbon resin was apply | coated to the surface layer of Sn containing layer, and the organic resin layer was formed in the one part test piece. Table 2 shows the compositions of the coatings B to G applied to the surface of the steel sheet. In addition, the state of non-coating (as blasting treatment) was made into "the coating film A" for convenience.

  In a strong acid environment, the coating film is likely to be lost during use, so the corrosion resistance to a strong acid was evaluated without a coating assuming long-term use. After measuring the weight of the unpainted (A) test piece, the sulfuric acid solution adjusted to pH 0 or pH 1 is sprayed on the entire surface of the test piece by spraying, and 24 vertically at an environment controlled to 30 ° C. and 100% RH. A corrosion test was carried out for 1 year to hold for a period of time. After the corrosion test, the weight of the test piece from which rust was removed with an ammonium citrate solution was measured, and the difference in weight before and after the test was calculated as the amount of corrosion loss. Evaluation was performed by the relative ratio of the amount of wear of each steel material when the amount of corrosion wear of the ordinary steel (Table 1, No. 14) which does not contain an alloy element is 100%. The smaller the relative ratio of corrosion loss, the better the corrosion resistance, and 30% or more is rated as ×, 30 to 15% as ○, and 15% or less as ◎. As a result, as shown in Table 3, it was found that the steel containing Cu and Sb is superior in corrosion resistance in a strong acid environment as compared to a steel containing only one of Cu and Sb.

  Next, for a test piece on which a coating containing no Sn-containing layer or Sn ion source is formed, two straight lines with a width of 0.6 mm and a length of 50 mm are viewed from above the test piece at the bottom of the test surface. The X cut which intersects at ° was inserted with a cutter to expose the ground iron surface. The X-cut simulates an inevitable defect. The corrosion test was done using these test pieces.

  A sulfuric acid solution adjusted to pH 2 was sprayed on the entire surface of the test piece by spraying, and a corrosion test was conducted for 1 year, where the test was held vertically for 24 hours under an environment controlled at 30 ° C. and 100% RH. After the corrosion test, after removing the peelable coating with a scraper, rust was removed with an ammonium citrate solution. Then, 17 points of corrosion depths were measured and made into average corrosion depth.

  The average corrosion depth of the combination of an ordinary alloy containing no alloying element (steel No. 14 in Table 1) and an epoxy resin not containing an Sn ion source and an Sb ion source (coating F in Table 2) is 100 It evaluated by the relative ratio of the average corrosion depth of various steel materials at the time of setting it as%. As the relative ratio of the average corrosion depth is smaller, the corrosion resistance is better, and 30% or more is evaluated as x, 30% to 15% as 、, and 15% or less as 、, the results are shown in Table 4-1 and Table 4-2. It was shown to.

  As shown in Table 4-1, steel No. 1 containing Cu and Sb. In the case of the steel material which formed coating-film BE which contains a Sn ion supply source in 1-10, corrosion resistance is favorable. On the other hand, as shown in Table 4-2, the coating films B to E containing the Sn ion source were treated with a steel No. 1 containing at least one of Cu and Sb. Coatings F and G which do not contain Sn ion source when formed into 11 to 14 are made of the steel No. When it is formed to 1 to 10, the superiority of the corrosion resistance to ordinary steel can not be seen.

  As described above, the corrosion resistant steel material for acidic environment of the present invention exhibits excellent corrosion resistance not only in a strong acid environment having a pH of less than 2 but also in a weak acid environment having a pH of 2 or more. It has the effect of suppressing the progression. On the other hand, as the test results show, in the case of a combination of steel and Cu-Sb simultaneously added with a coating not containing Sn ions, or a combination of steel without Sb and a coating containing Sn ions, The effect of suppressing the progress of the corrosion in the buttocks and the paint fragile portion was not found. Similarly, a steel material coated with Sb ions on steel materials to which Cu and Sn were simultaneously added without adding Sb was not found to have an effect of suppressing the progress of corrosion in the covering portion or the coating fragile portion. .

  According to the corrosion resistant steel material for acidic environment and the anticorrosion method of the present invention, for example, it becomes possible to improve the corrosion resistance of a steel structure or the like exposed to a weakly acidic environment by a hot spring area or acid rain. Moreover, the corrosion resistant steel material for acidic environment and the corrosion prevention method of the present invention are not only in a strong acid environment such as acid dew point corrosion, but also in an acid corrosive environment where pH fluctuates due to some factor and is exposed to a weak acid environment. It may develop excellent corrosion resistance. Therefore, the present invention is extremely significant for industrial contribution.

Claims (14)

In mass%,
C: 0.001 to 0.20%,
Si: 0.01 to 2.50%,
Mn: 0.10 to 2.00%,
Cu: 0.10 to 1.00%,
Sb: 0.01 to 0.20%
Contains
P: 0.05% or less,
S: A steel material limited to 0.05% or less and the balance being Fe and unavoidable impurities,
A Sn-containing layer containing a Sn ion supplying substance and a binder on the surface of the steel material or on a rust layer formed on the surface of the steel material;
The corrosion resistant steel material for an acidic environment, wherein the amount of the Sn ion supplying substance is 1 to 54 mass% in terms of metal Sn based on the total solid content mass of the Sn-containing layer. The above-mentioned steel material is further in mass%,
Mo: 1.00% or less,
W: 1.00% or less,
Ni: 1.00% or less,
Sn: 0.50% or less 1 type, or 2 or more types are contained, The corrosion resistant steel materials for acidic environments of Claim 1 characterized by the above-mentioned. The above-mentioned steel material is further in mass%,
Cr: 0.50% or less,
Ti: 0.150% or less,
Nb: 0.150% or less,
V: 0.50% or less,
Ta: 0.040% or less,
B: 0.010% or less of 1 type or 2 or more types is contained, The corrosion resistant steel material for acidic environments of Claim 1 or 2 characterized by the above-mentioned. The above-mentioned steel material is further in mass%,
Al: 0.10% or less,
Ca: 0.010% or less,
Mg: 0.010% or less,
REM: The corrosion resistant steel material for acidic environment according to any one of claims 1 to 3, which contains one or more of 0.010% or less. The Sn-containing layer further contains one or more acid-soluble metal ion-supplying materials that supply one or more of Cu ²⁺ ions, Ni ²⁺ ions, and Cr ³⁺ ions.
The total amount of the Sn ion supplying substance and the metal ion supplying substance is 65 in terms of metal Sn, metal Cu, metal Ni, and metal Cr with respect to the total solid mass of the Sn-containing layer. % Or less, The corrosion resistant steel materials for acidic environments in any one of Claims 1-4 characterized by the above-mentioned.   The corrosion resistant steel material for acidic environment according to any one of claims 1 to 5, further comprising an organic resin layer having a thickness of 10 to 100 μm on the Sn-containing layer.   The said Sn containing layer is a film thickness of 5-50 micrometers, The corrosion-resistant steel materials for acidic environments in any one of Claims 1-6 characterized by the above-mentioned. In mass%,
C: 0.001 to 0.20%,
Si: 0.01 to 2.50%,
Mn: 0.10 to 2.00%,
Cu: 0.10 to 1.00%,
Sb: 0.01 to 0.20%
Contains
P: 0.05% or less,
S: 0.05% or less limited, prepare the steel material whose remainder is Fe and unavoidable impurities,
The Sn ion supplying material is mixed with a binder to prepare a Sn-containing paint so that the amount of metal Sn is 1 to 54% by mass with respect to the total solid content mass,
A method for preventing corrosion comprising applying the Sn-containing coating on the surface of the steel material or on a rust layer formed on the surface of the steel material to form a Sn-containing layer. The above-mentioned steel material is further in mass%,
Mo: 1.00% or less,
W: 1.00% or less,
Ni: 1.00% or less,
The anticorrosion method according to claim 8, wherein one or more of 0.50% or less of Sn: 0.50% or less are contained. The above-mentioned steel material is further in mass%,
Cr: 0.50% or less,
Ti: 0.150% or less,
Nb: 0.150% or less,
V: 0.50% or less,
Ta: 0.040% or less,
The anticorrosion method according to claim 8 or 9, wherein B: at least one of 0.010% or less is contained. The above-mentioned steel material is further in mass%,
Al: 0.10% or less,
Ca: 0.010% or less,
Mg: 0.010% or less,
REM: One or more of 0.010% or less is contained, The anticorrosion method according to any one of claims 8 to 10, characterized in that   The Sn-containing paint is prepared by mixing the metal ion supplying substance with the binder so that the total of the Sn converted amount, the Cu converted amount, the Ni converted amount, and the Cr converted amount is 65% or less with respect to the total solid mass. The anticorrosion method according to any one of claims 8 to 11, characterized by preparing.   The anticorrosive method according to any one of claims 8 to 12, further comprising forming an organic resin layer having a thickness of 10 to 100 μm on the Sn-containing layer.   The anticorrosion method according to any one of claims 8 to 13, wherein the Sn-containing layer is formed to a thickness of 5 to 50 m.