JP2013028830A - Corrosion-resistant steel material for tank deck of crude oil tanker or for hold of bulk carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel material for a tank deck of a crude oil tanker or for a hold of a bulk carrier exhibiting excellent corrosion resistance even when exposed to a severe corrosion environment where a sulfur-containing material exists such as sulfur, sulfur oxide, or sulfide, and having weldability and hot workability equal to or higher than that of normal steel material for vessels.SOLUTION: The steel material for the tank deck of the oil tanker or for the hold of the bulk carrier includes C: 0.01-0.30% (mass%), Si: 0.20-1.0%, Mn: 0.50-1.60%, P: 0.005-0.040%, S: 0.005-0.020%, Al: 0.050-0.100%, Cu: 0.20-1.0%, Ni: 0.03% or less (including 0%), Cr: 0.05-0.30%, Zn: 0.001-0.50%, Sn: 0.005-0.050%, and Ca: 0.0005-0.0050%, with the balance being Fe and inevitable impurities.

Description

The present invention relates to a steel material for a tank upper deck of a crude oil tanker or a bulk carrier of a bulk carrier having excellent corrosion resistance. In particular, a severe corrosive environment in which corrosive gases such as hydrogen sulfide and SO ₂ / SO ₃ , coal, sulfur contained in oil, etc. (hereinafter, these may be collectively referred to as “sulfur-containing substances”) In particular, the present invention relates to a steel material for a tank upper deck of a crude oil tanker or a steel material for a hold of a bulk carrier, which exhibits excellent corrosion resistance.

  For the purpose of preventing leakage of fuel in steel materials that are used as structural materials and exposed to corrosive environments, such as crude oil tankers and bulk carriers, for the purpose of transporting fuel such as crude oil and coal. In general, some kind of anticorrosion means is applied. As anti-corrosion means, (a) anti-corrosion coating and (b) electro-corrosion prevention (for example, sacrificial anode such as zinc or electro-corrosion protection by an external power source) are conventionally known, and both are often used in combination.

  Among these, (a) anticorrosion coating is formed, for example, in a crude oil tank of a crude oil tanker. Specifically, in a crude oil tank of a crude oil tanker, corrosion due to a sulfur-containing substance is significant, and therefore, the surface of the steel material constituting the tank is often subjected to anticorrosion coating using an epoxy resin paint. This anti-corrosion coating is a corrosion protection means commonly used in ships, but the anti-corrosion performance may not be maintained due to wrinkles on the coating film or peeling of the coating due to external factors or deterioration over time. . Therefore, after anti-corrosion coating, periodic anti-corrosion performance inspection and maintenance are required, and there is a problem that the time and cost required for this maintenance are enormous.

  On the other hand, (b) cathodic protection is very effective for a portion where an electric circuit is formed by being completely immersed in an aqueous electrolyte solution such as seawater. However, in the gas phase part in the crude oil tank that is not immersed in the electrolyte aqueous solution or in the bulk of the bulk carrier, there is a problem that an electric circuit is not formed and the anticorrosion effect is insufficient.

  From the above, in order to improve ship safety and prolong the life, there is a need for steel materials that exhibit excellent corrosion resistance even in areas where the anticorrosion coating has deteriorated due to external factors, etc. Yes.

  In response to the above requirement, a technique for improving the corrosion resistance of the steel material itself by adjusting the chemical composition of the steel material has been proposed (for example, Patent Document 1). Specifically, in Patent Document 1, a steel added with Cr: more than 0.1 mass% and not more than 0.5 mass% and Cu: 0.03-0.4 mass% is added to W, Mo, Sn, Sb, Ni and Co. If one or two or more selected from among them are added and the components are made to satisfy a certain relationship, the corrosion resistance (entire surface resistance) in the tanker oil tank part, both naked and after painting Corrosion resistance, local corrosion resistance). Thus, it seems that by adjusting the chemical composition of the steel material, it is possible to ensure corrosion resistance that is somewhat better than conventional corrosion protection means.

  However, even in the severe corrosive environment where sulfur-containing substances are present, such as the bulk of a bulk carrier or the back side (crude oil side) of a crude oil tank deck, sufficient corrosion resistance should be ensured even with the technique of Patent Document 1. However, further improvement in corrosion resistance is required.

JP 2010-222701 A

  The present invention has been made by paying attention to the above-described circumstances, and its purpose is that when it is exposed to a severe corrosive environment where sulfur-containing substances such as sulfur, sulfur oxides and sulfides exist. However, it is necessary to provide a steel material for crude oil tanker tank upper deck or bulk carrier cargo that has excellent corrosion resistance and has weldability and hot workability equivalent to or better than ordinary ship structural steel. It is in.

  The steel material for the upper deck of the tank of the crude oil tanker or bulk carrier of the bulk tanker of the present invention that can solve the above problems is C: 0.01 to 0.30% (meaning mass%, the same applies hereinafter), Si: 0 20 to 1.0%, Mn: 0.50 to 1.60%, P: 0.005 to 0.040%, S: 0.005 to 0.020%, Al: 0.050 to 0.100 %, Cu: 0.20 to 1.0%, Ni: 0.03% or less (including 0%), Cr: 0.05 to 0.30%, Zn: 0.001 to 0.50%, Sn : 0.005 to 0.050%, and Ca: 0.0005 to 0.0050%, with the balance being made of Fe and inevitable impurities.

  The steel material may further contain Ti: 0.050% or less (not including 0%).

  The steel material further includes one or more elements selected from the group consisting of Co: 0.050% or less (not including 0%) and Mo: 0.050% or less (not including 0%). You may go out.

  The steel material further includes at least one element selected from the group consisting of Bi: 0.050% or less (not including 0%) and Sb: 0.050% or less (not including 0%). May be included.

  According to the present invention, by using a steel material satisfying a prescribed component composition, the effects described later are exhibited and excellent corrosion resistance can be ensured. The steel material of the present invention is suitably used particularly for a part exposed to a severe corrosive environment in which a sulfur-containing substance exists, that is, a tank upper deck of a crude oil tanker or a bulk carrier.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, the following knowledge was found and the present invention was completed.

  That is, in a corrosive environment, so-called iron rust such as iron oxide and iron oxyhydroxide is formed on the steel surface as a corrosion product. Conventionally, it is well known that these corrosion products protect the steel material surface and contribute to ensuring corrosion resistance.

  In order to improve the corrosion resistance in a severe corrosive environment in which a sulfur-containing substance exists such as a gas phase part in a crude oil tank or the bottom plate part of a bulk carrier, the present inventors have determined the corrosion mechanism of this corrosive environment and the corrosion mechanism. We have conducted intensive research on the relationship between corrosion products formed on steel surfaces in the environment and the corrosion resistance of steel materials. As a result, it was found that in a severe corrosive environment where the sulfur-containing substance is present, corrosion products other than iron rust also contribute to the development of corrosion resistance of the steel material.

In particular,
(I) a film formed by a precipitating compound such as Cu sulfide (precipitating compound film), and Cr _w O _x , Si _u O _v and the like formed by containing Cr, Si and P, and By forming two types of coatings with a stable oxide coating including P _y O _z (subscripts w, x, u, v, y, and z are variables, the same shall apply hereinafter), iron rust as a corrosion product is formed. It has been found that the corrosion resistance is remarkably improved as compared with the case where only the film is formed.

  In addition, as shown in the following (ii) to (v), especially as other components, Al, Zn, Sn, and Ca contribute to improvement of corrosion resistance. In the present invention, Ni inhibits improvement of corrosion resistance. It was also found that it is an element to do.

(Ii) By containing Al, the density of the oxide film is improved, and the formation rate of the oxide film containing Cr _w O _x , Si _u O _v and P _y O _z is increased, and this corrosion progresses. The formation of a rust layer that suppresses
(Iii) Ni is known to contribute to the formation of good iron rust and enhance the corrosion resistance of steel materials in conventional corrosion-resistant steel materials (for example, weathering steel materials). However, in a corrosive environment containing a large amount of S, Ni competes with Cu and adversely affects the formation of the precipitateable compound film (i). Ni also promotes a cathode reaction by reducing the hydrogen overvoltage in a corrosive environment containing a large amount of S. Therefore, in the present invention, it is necessary not to contain Ni or to be contained in a trace amount even if it is contained.
(Iv) By containing Zn and Sn, the hydrogen overvoltage of the steel material is increased, the cathode reaction is suppressed, and the corrosion resistance is increased.
(V) By containing Ca, the progress of pitting corrosion accompanying a local increase in hydrogen ion concentration is suppressed.

  And in this invention, while fully exhibiting the synergistic effect by said (i)-(v), as a result of examining a component composition in order to provide strength, toughness, weldability, etc. required as marine steel materials, I found out that it should be in the range.

  Hereinafter, the reason for defining the component range of the steel of the present invention will be described.

[C: 0.01 to 0.30%]
C is an element necessary for ensuring the strength of the steel material. In order to obtain the strength required as a structural member of a ship, it is necessary to contain 0.01% or more of C. The amount of C is preferably 0.07% or more, more preferably 0.10% or more, and further preferably 0.12% or more. On the other hand, if the C content exceeds 0.30%, the toughness deteriorates. Therefore, the upper limit of the C amount is set to 0.30%. The amount of C is preferably 0.26% or less, more preferably 0.23% or less, and still more preferably 0.20% or less.

[Si: 0.20 to 1.0%]
Si is an element effective for forming a Si oxide on the surface of a steel material in a corrosive environment and improving corrosion resistance. Such an action is particularly effective in an environment where corrosion progresses due to S. In this invention, in order to exhibit this effect, 0.20% or more of Si is contained. The amount of Si is preferably 0.31% or more, more preferably 0.40% or more, and further preferably 0.45% or more. On the other hand, when the amount of Si exceeds 1.0%, Si is locally segregated to cause rust swelling, which deteriorates the corrosion resistance. Therefore, the upper limit of the Si amount is set to 1.0%. A preferable upper limit of the amount of Si is 0.87%, a more preferable upper limit is 0.78%, and a further preferable upper limit is 0.68%.

[Mn: 0.50 to 1.60%]
Mn is an element that adversely affects corrosion resistance because it forms MnS by combining with S and local corrosion develops from its surroundings. Therefore, in the present invention, the upper limit of the amount of Mn is set to 1.60%. A preferable upper limit of the amount of Mn is 1.20%, a more preferable upper limit is 1.1%, and a further preferable upper limit is 1.0%. On the other hand, Mn is also an element necessary for deoxidation and ensuring strength. Therefore, the amount of Mn is 0.50% or more. Preferably it is 0.60% or more, More preferably, it is 0.75% or more, More preferably, it is 0.80% or more.

[P: 0.005 to 0.040%]
P is an element necessary for improving the corrosion resistance because it has the effect of stabilizing the sulfide of Cu by generating phosphate when the steel surface is oxidized in a corrosive environment. In order to obtain such an effect, the P amount needs to be 0.005% or more. The amount of P is preferably 0.010% or more, more preferably 0.013% or more, and still more preferably 0.015% or more. However, when P is excessively contained, phosphoric acid is locally concentrated and may cause pitting corrosion. Therefore, in the present invention, the P content is 0.040% or less. Preferably it is 0.034% or less, More preferably, it is 0.030% or less, More preferably, it is 0.025% or less.

[S: 0.005 to 0.020%]
S, when eluted in a corrosive environment, is an element necessary for improving the corrosion resistance because it has a function of reducing the corrosion dissolution reaction by forming a precipitateable compound film on the surface of the steel material together with Cu. Such an effect is significant when S exists in a corrosive environment. In order to fully exhibit this effect, the S amount is set to 0.005% or more in the present invention. Preferably it is 0.008% or more, More preferably, it is 0.010% or more. On the other hand, when S is contained excessively, unnecessary S binds to hydrogen ions and promotes the cathode reaction, causing pitting corrosion, which in turn deteriorates the corrosion resistance. Therefore, the S amount is 0.020% or less. Preferably it is 0.017% or less, More preferably, it is 0.015% or less.

[Al: 0.050 to 0.100%]
Al is an element necessary for improving the corrosion resistance because it has a function of generating a stable Al oxide film on the steel surface and reducing the corrosion dissolution reaction. In addition, as described above, the density of the oxide film is improved, and the formation rate of the oxide film containing Cr _w O _x , Si _u O _v and P _y O _z is increased, thereby forming a rust layer that suppresses the progress of corrosion. It is an effective element that can enhance the corrosion resistance by being promoted. Furthermore, it is also an element necessary for deoxidation and securing of strength, like Si and Mn. In order to exhibit these effects, in the present invention, the amount of Al is made 0.050% or more. Preferably it is 0.056% or more, More preferably, it is 0.061% or more, More preferably, it is 0.065% or more. On the other hand, if Al exceeds 0.100% and is excessively contained, Al is segregated locally, causing rust swelling and deteriorating corrosion resistance. Therefore, in the present invention, the upper limit of the Al amount is set to 0.100%. A preferred upper limit is 0.085%, a more preferred upper limit is 0.080%, a still more preferred upper limit is 0.075%, and a particularly preferred upper limit is 0.070%.

[Cu: 0.20 to 1.0%]
When Cu elutes in a corrosive environment, it has a function of reducing the corrosion reaction by forming a dense precipitateable compound (Cu sulfide) film on the surface of the steel material, and is an element necessary for improving corrosion resistance. It is. In order to sufficiently exhibit such an effect, the Cu content is set to 0.20% or more. Preferably it is 0.25% or more, more preferably 0.30% or more. However, when Cu is excessively contained, not only deterioration of weldability and hot workability occurs, but also local corrosion may occur due to a potential difference between Cu in the steel and its periphery. Therefore, the Cu amount is 1.0% or less. Preferably it is 0.78% or less, More preferably, it is 0.65% or less, More preferably, it is 0.50% or less.

[Ni: 0.03% or less (including 0%)]
As described above, Ni is an element that generally improves the corrosion resistance. However, in a corrosive environment containing a large amount of S, the cathode reaction is greatly promoted to cause pitting corrosion and to deteriorate the corrosion resistance. In a corrosive environment containing a large amount of S, Ni competes with Cu and adversely affects the formation of a precipitating compound film. Therefore, in the present invention, the amount of Ni is suppressed to 0.03% or less. Preferably it is 0.01% or less, Most preferably, it is 0%.

[Cr: 0.05-0.30%]
Cr, when eluted in a corrosive environment, has a function of reducing the corrosion reaction by forming a dense precipitating compound film on the steel surface, and is an element necessary for improving corrosion resistance. In order to exert such effects, it is necessary to contain 0.05% or more of Cr. The amount of Cr is preferably 0.11% or more, more preferably 0.13% or more, and still more preferably 0.15% or more. However, when Cr is excessively contained, the pH of the corrosion tip portion is lowered and pitting corrosion tends to occur, and the corrosion resistance is deteriorated. Therefore, in the present invention, the Cr content is 0.30% or less. Preferably it is 0.27% or less, More preferably, it is 0.23% or less.

[Zn: 0.001 to 0.50%]
When Zn is contained in the steel material, it has an effect of improving the corrosion resistance by increasing the hydrogen overvoltage on the steel material surface in a corrosive environment and suppressing the cathode reaction. Moreover, like Cu, it has the effect | action which forms a precise | minute precipitation compound film | membrane on the steel material surface, and reduces a corrosion reaction. In this invention, in order to fully exhibit these effects, Zn is contained 0.001% or more. Preferably it is 0.005% or more, More preferably, it is 0.015% or more, More preferably, it is 0.020% or more, Most preferably, it is 0.025% or more. On the other hand, when Zn is excessively contained, local corrosion occurs due to a potential difference between Zn in the steel and its periphery. Therefore, in the present invention, the upper limit of Zn content is set to 0.50%. A preferable upper limit is 0.33%, a more preferable upper limit is 0.10%, and a still more preferable upper limit is 0.065%.

[Sn: 0.005 to 0.050%]
Sn, like Zn, has the effect of increasing the hydrogen overvoltage on the steel surface and suppressing the cathode reaction. Moreover, like Cu, it has the effect | action which forms a precise | minute precipitation compound film | membrane on the steel material surface, and reduces a corrosion reaction. In order to exhibit these effects, the amount of Sn is made 0.005% or more. Preferably it is 0.010% or more, More preferably, it is 0.014% or more. On the other hand, if Sn is excessively contained, local corrosion occurs due to a potential difference between Sn in the steel and its surroundings, and the corrosion resistance is lowered. Therefore, the upper limit of Sn content is 0.050%. A preferable upper limit is 0.045%, a more preferable upper limit is 0.040%, and a still more preferable upper limit is 0.035%.

[Ca: 0.0005 to 0.0050%]
When pitting corrosion occurs in a corrosive environment, the progress of pitting corrosion occurs with a local increase in hydrogen ion concentration. Ca is an element that dissolves in pitting corrosion and suppresses the decrease in pH and suppresses the development of pitting corrosion. In order to exert the effect of Ca, the Ca content is set to 0.0005% or more in the present invention. Preferably it is 0.0012% or more. However, if Ca is excessively contained, Ca is segregated locally to cause rust swelling and deteriorate the corrosion resistance. Therefore, in the present invention, the upper limit of the Ca content is set to 0.0050%. A preferred upper limit is 0.0043%.

  The basic component composition of the steel of the present invention is as described above, and the balance is composed of iron and inevitable impurities. Moreover, as shown below, in addition to the above elements, Ti, Co and / or Mo, Bi and / or Sb can be further added to further enhance the corrosion resistance.

[Ti: 0.050% or less (excluding 0%)]
When pitting corrosion occurs in a corrosive environment, Ti is an element useful for ensuring corrosion resistance by dissolving in the pitting corrosion and suppressing a decrease in pH and suppressing the progress of pitting corrosion. In order to exhibit this effect, it is preferable to contain Ti 0.010% or more. More preferably, it is 0.015% or more. On the other hand, when the amount of Ti is excessive, Ti is segregated locally and causes rust expansion, thereby deteriorating the corrosion resistance. From the above viewpoint, the upper limit of the Ti content is preferably 0.050%. A more preferred upper limit is 0.045%.

[Co: one or more elements selected from the group consisting of 0.050% or less (not including 0%) and Mo: 0.050% or less (not including 0%)]
Co is an element effective for improving the corrosion resistance, and can be contained as necessary. In detail, Co has the effect | action which forms the film containing a stable Co oxide on the steel material surface, and reduces a corrosion dissolution reaction. In order to exhibit this effect, it is preferable to make it contain 0.001% or more, More preferably, it is 0.005% or more. However, if the amount of Co exceeds 0.050%, Co is segregated locally, causing rust swelling and deteriorating corrosion resistance. Therefore, when Co is contained, the upper limit of the Co amount is preferably 0.050%. More preferably, it is 0.041% or less.

  Mo is also an element effective for improving the corrosion resistance, and can be contained as necessary. In detail, Mo has the effect | action which forms the film | membrane containing a stable Mo oxide on the steel material surface similarly to said Co, and reduces a corrosion dissolution reaction. In order to exhibit this effect, it is preferable to make it contain 0.001% or more, More preferably, it is 0.005% or more. However, if the amount of Mo exceeds 0.050%, Mo is segregated locally, causing rust swelling and deteriorating corrosion resistance. Therefore, when Mo is contained, the upper limit of the Mo amount is preferably 0.050%. More preferably, it is 0.040% or less.

[Bi: one or more elements selected from the group consisting of 0.050% or less (not including 0%) and Sb: 0.050% or less (not including 0%)]
Bi is an element effective for improving the corrosion resistance, and can be contained as necessary. Specifically, Bi is an element that, when eluted in a corrosive environment, forms a dense precipitating compound film on the surface of the steel material and reduces the corrosion reaction, thereby improving the corrosion resistance. In order to exhibit such an effect, it is preferable to contain Bi 0.010% or more. More preferably, it is 0.014% or more. However, if Bi is excessively contained, not only the weldability and hot workability deteriorate, but also local corrosion occurs due to the potential difference between Bi in the steel and its surroundings. Therefore, the Bi amount is preferably 0.050% or less. More preferably, it is 0.046% or less.

  Sb is also an element effective in improving corrosion resistance, and can be contained as necessary. Specifically, Sb is an element that improves the corrosion resistance by forming a dense precipitating compound film on the surface of the steel material and reducing the corrosion reaction when eluted in a corrosive environment, as in the case of Bi. In order to exert such an effect, it is preferable to contain 0.010% or more of Sb. More preferably, it is 0.014% or more. However, when Sb is contained excessively, not only the weldability and hot workability deteriorate, but also local corrosion occurs due to the potential difference between Sb in the steel and its surroundings. Therefore, the Sb content is preferably 0.050% or less. More preferably, it is 0.046% or less.

  The steel material of this invention can be manufactured on the conditions currently performed except adjusting the said component composition.

  The steel material of the present invention is used particularly in a part exposed to a severe corrosive environment in which a sulfur-containing substance is present, that is, a tank upper deck of a crude oil tanker or a bulk carrier. Since the steel material of the present invention is excellent in corrosion resistance, it can be used for a tank upper deck of the above-mentioned crude oil tanker or a bulk carrier of a bulk carrier without painting. Moreover, you may perform the process of a zinc rich paint, a shop primer, etc. for the purpose of the initial rust prevention as needed. Even if it is painted, it can be used without problems. Examples of the paint used for the coating include tar epoxy resin paints, modified epoxy resin paints, and other representative heavy anticorrosion paints. Moreover, you may use together with other anti-corrosion methods, such as cathodic protection (galvanic anode method, external power supply method).

  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 satisfying the component compositions shown in Tables 1 and 2 (the balance being iron and inevitable impurities) were melted in an electric furnace, hot-rolled and subjected to heat treatment as needed to obtain a steel material having a plate thickness of 10 mm. And the test piece (TP) of size 30x30x5 (mm) was cut out from this steel raw material. Next, the entire surface of TP was polished up to SiC # 600 with a wet rotary polishing machine, washed with water and acetone, dried, and then used for the following tests.

[Corrosion test method]
Using the TP, a corrosion test was conducted by immersing in a 0.01 mol aqueous sulfuric acid solution (room temperature) for 3 days, simulating the tank upper structure of a crude oil tanker and the hold of a bulk carrier (Vulker). In this corrosion test, No. 1 shown in Tables 1 and 2 was used. Five TPs of 1 to 55 steel materials were used. After the immersion, TP is immersed in a 10% aqueous solution of diammonium hydrogen citrate (room temperature) to perform cathodic electrolysis, and after removing the corrosion products formed on the TP surface, washing with water and acetone, and drying Then, the TP surface shape was evaluated as follows.

[Evaluation of TP surface shape]
The three measurement parameters representing corrosion were “1. Presence / absence of pitting”, “2. Presence / absence of local corrosion” and “3. Presence / absence of surface swelling”. The evaluation criteria for these measurement parameters 1 to 3 are as follows. For each measurement parameter, the case where 4 or more of the 5 TPs were free from the following corrosion was evaluated as ◯, the case where 3 of the 5 TPs were free from the following corrosion was evaluated as △, and the others were evaluated as ×. As a comprehensive judgment, among the above three types of measurement parameters, all of 1 to 3 were evaluated as ◎, 2 out of 1 to 3 as ◯, and 1 as △, and the others as ×. The results are shown in Tables 1 and 2.

(Measurement parameter evaluation criteria)
1. Presence / absence of pitting corrosion ... It was judged that pitting corrosion was present when 5 or more holes having a diameter (equivalent diameter of circle) of 0.5 mm or more were dispersed on the steel surface (30 mm x 30 mm front and back surfaces). . Note that one having two or more holes attached was counted as one.
2. Presence / absence of local corrosion: A case where even one hole having a diameter (equivalent circle diameter) of 1.0 mm or more was generated on the side surface of steel (4 surfaces of 30 mm × 5 mm) was judged to be local corrosion.
3. Presence / absence of surface bulge: A case where 10 or more hemispheres having a diameter (equivalent circle diameter) of 0.1 mm or more were distributed on the TP surface was judged as “surface bulge”.

  From Tables 1 and 2, the following can be considered. That is, it can be seen that those satisfying the specified component composition in the present invention hardly exhibit any pitting corrosion, local corrosion, or blistering in the corrosion test, and exhibit excellent corrosion resistance. On the other hand, those not satisfying the specified component composition in the present invention are remarkably corroded and inferior in corrosion resistance.

Claims (4)

C: 0.01 to 0.30% (meaning mass%, the same shall apply hereinafter)
Si: 0.20 to 1.0%,
Mn: 0.50 to 1.60%
P: 0.005-0.040%,
S: 0.005-0.020%,
Al: 0.050-0.100%
Cu: 0.20 to 1.0%,
Ni: 0.03% or less (including 0%),
Cr: 0.05-0.30%,
Zn: 0.001 to 0.50%
Sn: 0.005-0.050% and Ca: 0.0005-0.0050%
A steel material for a tank upper deck of a crude oil tanker having excellent corrosion resistance, or a bulk carrier of a bulk carrier, characterized by satisfying   The steel material according to claim 1, further comprising Ti: 0.050% or less (not including 0%). Furthermore,
Co: 0.050% or less (not including 0%) and Mo: 0.050% or less (not including 0%)
The steel material of Claim 1 or 2 containing the 1 or more types of element selected from the group which consists of. Furthermore,
Bi: 0.050% or less (not including 0%), and Sb: 0.050% or less (not including 0%)
The steel material in any one of Claims 1-3 containing the 1 or more types of element selected from the group which consists of.