United States Patent (19) -S

United States Patent (19) 11 Patent Number: 4,731,295 Yamamoto et al. 45 Date of Patent: Mar. 15, 1988

(54) COATING COMPOSITION FOR 56 References Cited CONTROLLING HYDROGEN ABSORPTION U.S. PATENT DOCUMENTS 75 Inventors: Takashi Yamamoto, Souraku; 3,474,301 10/1969 Shohji et al...... 317/234 Toshihiro Okai, Katano; Mitsuyuki 3,594,339 7/1971 Palaika ...... 524/43 Oda, Kyoto, all of Japan 3,956,231 5/1976 Moore et al. . ... 524/406 73 Assignee: Nippon Paint Co., Ltd., Osaka, Japan 4,407,899 10/1983 Hara et al...... 428/629 21 Appl. No.: 881,581 FOREIGN PATENT DOCUMENTS (22 Filed: Jul. 2, 1986 1344512 1/1974 United Kingdom. Primary Examiner-Theodore Morris Related U.S. Application Data Attorney, Agent, or Firm-Wenderoth, Lind & Ponack 63 Continuation-in-part of Ser. No. 663,451, Oct. 22, 1984, abandoned. 57 ABSTRACT 30 Foreign Application Priority Data There is herein provided a coating composition for Oct. 22, 1983 P Japan ...... S8-198022 controlling hydrogen embrittlement of a steel which Oct. 29, 1983 JP Japan ...... 58-2O3362 contains 1 to 500 percent by weight of a metal oxide Feb. 9, 1984 JP Japan ...... 59-23873 selected from the group consisting of manganese diox ide, vanadium pentoxide and molybdenum trioxide 51 Int. Cl* ...... B32B 11/OO 52 U.S. C...... 428/472; 428/450; based on 100 percent by weight of resin solids. 428/458 58) Field of Search ...... 324/413 1 Claim, 5 Drawing Figures

O 2 -S9

O O 5 2 O 5

OO 2OO TIME (t) U.S. Patent Mar. 15, 1988 Sheet 1 of 4 4,731,295

2 CO 'd 2 as to 1. O O 2 9 5

O OO 2OO TIME (t) Fig. 1 U.S. Patent Mar. 15, 1988 Sheet 2 of 4 4,731,295

O 2 3 O On 5. O C - . C up P2 5 s 5i -O3-A

2 O Of O 1. 1. O O -O.6 O OO 2OO TIME (t) Fig. 2 U.S. Patent Mar. 15, 1988 Sheet 3 of 4 4,731,295

Afg. 3

U.S. Patent Mar. 15, 1988 Sheet 4 of 4 4,731,295

Afg. 4

O.2

O V2O5 2.MnO 2 MOO3 \ h O MOO3 O.5 \s MnO2 ------to------f-- - - - OO 2OO 3OO 5OO 1 OOO Immersing time (h)

Expected MnO2 rise up time MnO2 N/Moo3 N

5OOh 8OOh OO 2OO 3OO 5OO OOO Immersing time (h) 4,731,295 1. 2 FIG. 5 shows the change in reaction current vs. in COATING COMPOST ON FOR CONTROLLING mersion time for the metal oxide coating on a steel HYDROGEN ABSORPTION panel, in accordance with the present invention. This application is a continuation-in-part of now 5 DETAILED DESCRIPTION OF THE abandoned application Ser. No. 663,451, filed Oct. 22, INVENTION 1984, now abandoned. Examples of manganese dioxide are natural manga nese dioxide, electrolytic manganese dioxide, chemical FIELD OF THE INVENTION synthesis manganese dioxide and a mixture thereof. The present invention relates to a coating composi 10 Electrolytic manganese dioxide is generally prepared tion for controlling hydrogen absorption of a steel, by an electrolysis of manganese sulfate or manganese more particularly, a coating composition for preventing chloride. Chemical manganese dioxide is prepared by a hydrogen embrittlement cracking which is the hydro decomposition of a permanganate with hydrochloric gen induced cracking arising from the absorbed hydro acid, an oxidation of manganese sulfate or a thermal gen atoms into the steel, formed by corrosion of the 15 decomposition of manganese nitrate. steel. Vanadium pentoxide can be prepared by any conven tional method such as the baking of lower oxides, ni BACKGROUND OF THE INVENTION trides or sulfides of vanadium. A steel produces a stress corrosion cracking in the Molybdenum trioxide can be prepared by any con presence of hydrogen sulfide or carbonic acid gas. It is ventional method such as baking in air or a reaction believed that a part of hydrogen formed from a reaction with nitric acid of molybdenum metals, or lower oxides of hydrogen sulfide with the steel is absorbed and dif or sulfide of molybdenum metals. Also heating of phos fused into the steel in the form of the atomic state to phorus molybdate or heating of ammonium molybdate result in the hydrogen embrittlement cracking. with nitric acid can be employed. In order to prevent the hydrogen embrittlement, a 25 The particle size of the metal oxide is the same as a coating or a lining has been used, by which corrosive pigment. A bigger particle size gives insufficient film reagents such as hydrogen sulfide are prevented from properties. contacting the steel. Typical examples are the method The vehicle used in the present invention is generally of adding a metallic powder (pigment) reactive with for a coating or a lining, for example a polymerized oil, hydrogen sulfide to a coating composition and the 30 a natural or synthetic resin, or a mixture thereof. method of adding an ion-exchange resin to a coating A typical example of the polymerized oil is the boiled composition. The former prevents contact between oil. Examples of the natural or synthetic resin are an hydrogen sulfide and the surface of the steel by the epoxy resin, an epoxy-urethane resin, an epoxy coal tar reaction of hydrogen sulfide with the metallic powder. resin, a melamine resin, a rubber chloride, a phenol The latter prevents contact between hydrogen sulfide 35 resin, a polyester resin, a polyurethane resin, a silicon and the surface of the steel by the reaction of hydrogen resin, a fluororesin, and the like. sulfide with the ion-exchange resin. According to the present invention, the metal oxide is The above methods are based on the reaction of hy formulated into the coating composition in an amount drogen sulfide with the additive such as the pigment or of 1 to 500 percent by weight, preferably 5 to 100 per the ion-exchange resin. The reaction, however, can not cent by weight based on 100 percent by weight of resin continue forever, that is, the technical effect of the solids. Amounts of more than 500 percent by weight are additive would reduce rapidly and the corrosion reac undesirable because of insufficient film properties. tion would begin to increase if the reactivity of the Amounts less than 1 percent by weight are undesirable additive decreases. According to the above methods, because the technical effect of the present invention the corrosion reaction generally begins to increase after 45 cannot be provided. 30 hours to 100 days from an application of the coating To the coating composition of the present invention composition. This term falls short of the actual service is added water or another solvent to form a dispersion. life of the steel (50-60 years). Examples of solvents are those used in the usual coat ings such as ketones, esters, glycols, alcohols, hydrocar SUMMARY OF THE INVENTION 50 bons. Also conventional type pigments or other addi The present invention provides a coating composi tives can be added to the coating composition of the tion for controlling a hydrogen absorption which con present invention, Examples of the additives are a plasti tains 1 to 500 percent by weight of a metal oxide se cizer, a surfactant, a drying agent, a curing agent, a lected from the group consisting of manganese dioxide, thickener, an anti-sagging agent, and the like. vanadium pentoxide and molybdenum trioxide based on 55 The steel to be treated by the coating composition of 100 percent by weight of resin solids. the present invention is one which can form or easily forms stress corrosion, hydrogen embrittlement, hydro BRIEF DESCRIPTION OF THE DRAWINGS gen induced cracking, hydrogen blisters and the like. FIG. 1 shows change with time of reaction current to Typical examples of the steel are carbon steel, alloys, extraction of hydrogen. high tensile strength steel and the like which are used FIG. 2 shows change with time of corrosion potential for oil field pipes, transfer line pipes, bolts, assembly of of the coated side of steel. a ship and the like. FIG. 3 shows an apparatus used to measure the The process for coating can be any conventional change of corrosion potential of a steel plate coated process such as flow, dipping, spray, brush, or powder with a gel containing oxides. 65 coating. FIG. 4 shows the change in corrosion potential vs. The substrate coated by the coating composition of immersion time for a steel panel coated with a composi the present invention hardly absorbs the atomic state tion of the present invention. hydrogen formed by the corrosion of the steel under the 4,731,295 3 4. atmosphere containing hydrogen sulfate. Accordingly, ent invention in the amount of manganese dioxide and the coating composition of the present invention effec was applied to the cold rolled steel. tively controls the hydrogen embrittlement. It is be In order to evaluate the controlling property of hy lieved that the reason why the present coating composi drogen absorption, a change on standing of the current tion prevents the hydrogen embrittlement is that the 5 caused by the reaction, H-H +e, which is an ex corrosion potential of the steel surface is kept noble by tract reaction of hydrogen on the other side of the steel, the metal oxide of the present invention (the absorption was measured. The measuring process was based on the of the atomic state hydrogen would be accelerated if the method described in Japanese Pat. No. 1018241, the corrosion potential of the steel surface is a less-noble portions of which are hereby incorporated by refer potential). 10 ence. The present invention is illustrated by the following The method of the evaluation is illustrated with refer examples, which, however, are not to be construed as ring to FIG. 1. The curve X of FIG. 1 shows a change limiting the invention to their details. All parts and on standing of a reaction current to an extract of hydro percentages in the examples are by weight unless other- gen with using the paint not containing manganase wise specified. 15 dioxide of the present invention, and the curve Y of EXAMPLE I FIG. 1 shows a change of standing of a reaction current to an extract of hydrogen with using the paint described A paint was prepared by the formulation as shown in in this example. Increase of the reaction current shows Table-1 and was applied to a cold rolled steel (thickness that the hydrogen was absorbed into the steel by a cor 0.8 mm, JIS G 3141) under the condition as shown in 20 rosion reaction of the steel surface under the film is Table-1. Instead of the cold rolled steel, the use of a extracted from the opposite side of the steel. Accord high tensile steel is naturally required for an evaluation ingly, the latter build up time of a curve shows the of the hydrogen embrittlement crack, but since the better corrosion control property. In FIG. 1, tx or ty technical effect of the present invention can be evalu- indicates the build up time. The rate of this build up ated by the degree of the hydrogen absorption is the 25 times between the curve X and the curve Y, i.e. ty/tx steel, the cold rolled steel was used in the present exam- can indicate the technical effect of the present inven ple. The method of coating was a spray coating. tion. The result and the condition of the corrosion is For the purpose of comparison, a paint was prepared shown in Table 1. by using the formulation outside the range of the pres TABLE 1. a type of manganese dioxide thickness Example and loading (parts) based on of film ty/tx number name of paint resin solids 100 parts drying condition (um) ratio corrosion condition 1 SUPERLAC DIF, F-80, N-23 natural manganese dioxide) 190° C./10 sec. 20 160 Hydrogen sulfide and (epoxy polyurethan paint) 100 parts carbonic acid were continuously blown into 3% NaCl solution. Temp. 50 C. 2 COPON MASTIC PRIMER natural manganese dioxide natural drying 70 72 Hydrogen sulfide and (epoxy resin paint) 100 parts 10 days carbonic acid were continuously blown into 3% NaCl. solution. Temp. 70° C. 3 EPOTARS (JIS K-566) natural manganese dioxide natural drying 40 21 Hydrogen sulfide and (epoxy coal tar paint) 100 parts 10 days carbonic acid were continuously blown into 3% NaCl solution. Temp. 50° C. 4. Hi-RUBBERE PRIMER natural manganese dioxide natural drying 25 15 Hydrogen sulfide and (rubber chloride paint) 100 parts 10 days carbonic acid were continuously blown into 3% NaCl solution. Temp. 30° C. 5 SULPHOTITE 10 natural manganese dioxide natural drying 25 120 Hydrogen sulfide gas (phenol resin paint) 100 parts 10 days of 100% relative humidity. Temp. 70' C. 6 SUNFTAL (JIS K-5572) natural manganese dioxide natural drying 25 78 Hydrogen sulfide gas (phthalic acid paint) 100 parts 10 days of 100% relative humidity. Temp. 70° C. 7 ORGA 100-2 natural manganese dioxide natural drying 20 34 Hydrogen sulfide gas (melamine resin paint) 100 parts 10 days of 100% relative humidity, Temp. 30° C. 8 CYANAMID HELGON QD natural manganese dioxide natural drying 35 23 Hydrogen sulfide and (JIS K5625-2) 100 parts 10 days carbonic acid were continuously blown into 3% NaCl solution. Temp. 30 C. 9 INTERGARD GLASS FLAKE natural manganese dioxide natural drying 2000 15 Hydrogen sulfide was (epoxy resin paint) 100 parts 10 days continuously blown into 3% NaC solution. Temp. 60° C. 10 NIPPE ZINKY 000P natural manganese dioxide natural drying 20 25 Hydrogen sulfide was (zinc powder containing 100 parts 10 days continuously biown paint) into 3% NaCl

4,731,295 5 6 TABLE 1-continued a type of manganese dioxide thickness Example and loading (parts) based on of film ty/tx number name of paint resin solids 100 parts drying condition (un) ratio corrosion condition solution. Temp. 20 C. Hi-CR PRIMER WHITE natural manganese dioxide natural drying 20 95 Hydrogen sulfide was (JIS K-5506) 100 parts 10 days continuously blown (synthetic resin paint) into 3% NaCl solution. Temp. 50 C. 2 POWDAXP natural manganese dioxide - 180 C./30 min. 100 17 Hydrogen sulfide and (powder coating) electrolytic manganese carbonic acid were dioxide) 100 parts continuously blown into 3% NaCl solution. Temp. 70 C. 13 ORGA 1002 electrolytic manganese natural drying 20 105 Hydrogen sulfide was (melamine resin paint) dioxide 10 parts 10 days continuously blown into 3% NaCl solution. Temp. 40 C. 14 ORGA 100-2 synthetic manganese dioxide) natural drying 20 175 Hydrogen sulfide was (melamine resin paint) 10 parts 10 days continuously blown into 3% NaCl solution. Temp. 40 C. 1S HCR PRIMER WHITE synthetic manganese dioxide natural drying O 43 Hydrogen sulfide of (JIS K-5506) l parts more than 10 days 100% relative (synthetic resin paint) humidity. Temp. 60 C. 6 Hi-CR PRIMER WHITE synthetic manganese dioxide natural drying O 120 Hydrogen sulfide gas (JIS K-5506) 10 parts more than 10 days of 100% relative (synthetic resin paint) humidity. Temp. 60 C. 17 Hi-CR PRIMER WHITE synthetic manganese dioxide natural drying O 32 Hydrogen sulfide gas (JIS K-5506) 100 parts more than 10 days of 100% relative (synthetic resin paint) humidity. Temp. 60 C. 18 Hi-CR PRIMER WHITE synthetic manganese dioxide natural drying O 14 Hydrogen sulfide gas (JIS K-5506) 500 parts more than 10 days of 100% relative (synthetic resin paint) humidity. Temp. 60 C. Coral Hi-CR PRIMER WHITE synthetic manganese dioxide natural drying 10 3 Hydrogen sulfide gas parative (JIS K-5506) 0.1 parts more than 10 days of 100% relative Example (synthetic resin paint) humidity. Temp. 60° C. Con. Hi-CR PRIMER WHITE synthetic manganese dioxide natural drying O 2 Hydrogen sulfide gas parative (JIS K-5506) 1000 parts more than 10 days of 100% relative Example (synthetic resin paint) humidity. Temp. 2 60 C. Use of 6 - MnO2 type pyrolusite y - MnO, (a - MnO2 (4)g. MnO2

Since this measurement is conducted by an electro EXAMPLE II chemical method, it is 100 times more sensitive than a 45 A paint was prepared by the formulation as showed conventional gas measurement. Accordingly, measur in Table-2 and was applied to a cold rolled steel (thick ing time of ty is stopped at 1,000 hours, and ty is re ness 0.8 mm, JIS G 3141) under the condition as shown garded as 1,000 unless the ty point is observed. in Table-2. In Table 1, ty/tx of Example 9 was as small as 15, For the purpose of comparison, a paint was prepared Example 9, however, was seemingly small, because it 50 by using the formulation outside the range of the pres was a thick coating type (a kind of lining) which made ent invention in the amount of vanadium pentoxide and ty more than 1,000 hours. Accordingly it seems that the was applied to the cold rolled steel. technical effect is more than 15 times greater when An evaluation was conducted as generally described manganese dioxide is present in the paint. 55 in Example I. The result is shown in Table 2.

4,731,295 10 Since this measurement is conducted by an electro chemical method, it is 100 times more sensitive than a EXAMPLE III conventional gas measurement. Accordingly, the mea A paint was prepared by the formulation as showed suring time ofty is stopped at 3,000 hours, tyisregarded in Table-3 and was applied to a cold rolled steel (thick ness 0.8 mm, JIS G 3141) under the condition as shown as 3,000 unless the typoint exists. in Table-3. In Table 2, ty/tx of Example 27 was as small as 38, For the purpose of comparison, a paint was prepared Example 27, however, was seemingly small, because it by using the formulation outside the range of the pres was a thick coating type (a kind of lining) which made ent invention in the amount of molybdenum trioxide ty more than 3,000 hours. Accordingly it seems that the 10 and was applied to the cold rolled steel. technical effect is more than 38 times greater when An evaluation was conducted as generally described vanadium pentoxide is present in the paint. in Example I. The result is shown in Table 3.

4,731,295 13 14 Since this measurement is conducted by an electro to a Pt counter-electrode 11 around the rugin tube 6. chemical method, it is 100 times more sensitive than a Corrosion potential (Ecorr.) before and after blowing conventional gas measurement. Accordingly, the mea an H2S was measured by a polarization curve method. suring time ofty is stopped at 3,000 hours, ty is regarded The H2S gas was continuously blown into the NaCl as 3,000 unless the typoint exists. solution 5 at 25 C. for one day. The same test were In Table 3, ty/tx of Example 43 was as small as 18, applied to MoC)3, electrolytic MnO2, 3-MnO2 and Example 43, however, was seemingly small, because it TiO2. The result was shown in Table 4. was a thick coating type (a kind of lining) which made ty more than 3,000 hours. Accordingly it seems that the TABLE 4 technical effect is more than 18 times greater when Ecorr. (mV) O Weight Before After molybdenum trioxide is present in the paint. metal oxides increase H2S blow H2S blow Difference EXAMPLE IV V2O5 --5% -65 -610 --5 Moos --12 -620 - 610 -- 10 This example indicates that the coating composition EMD (electro- --30 -590 - 700 - 110 of the present invention holds the potential of the steel lytic MnO) surface noble by measuring a corrosion potential on the 15 RMnO2 --25 -620 -690 - 70 side of the coating. TiO2 -- 1 -640 - 660 -20 One hundred parts by weight of melamine alkyd resin was mixed with 10 parts of a metal oxide of the present As appears from Table 4, V2O5 and MoC)3 have less invention (Y-1), 10 parts of titanium oxide(X-1) and 10 weight increase in Example V and maintain noble cor parts of iron oxide redOX-2) to form a paint. The paint 20 rosion potential after finishing the reaction with H2S in was applied to the cold rolled steel as described in Ex Example VI. ample 1. A saturated solution of 3% NaCl--H2S(gas) was contacted with the coated film. A silver-silver chlo EXAMPLE VII ride reference electrode was put into the saturated solu This example shows how the metal oxide of the pres tion through a salt bridge. The corrosion potential of ? ent invention provides the capability of maintaining the steel is measured on a basis of the silver-silver chlo noble Ecorr. in the presence of H2S. ride electrode. The result is shown in FIG. 2. A melamine alkyd coating composition was formu As indicated in FIG. 2, when the paint did not con lated with g-MnO2, V2O5 and MoC)3, respectively, in an tain the metal oxide of the present invention or when amount of 50 parts by weight based on 100 parts by the paint contained the substance which can react with 30 weight of resin solids to form three compositions. The hydrogen sulfide, the corrosion potential of the steel compositions were applied to steel panels in a thickness was not kept noble and changed to less-noble with time. of 30 to 35 um and were baked for 30 minutes at 140 C. On the other hand, when the paint prepared according The corrosion potential was measured using the appara to the present invention was used, the corrosion poten tus mentioned in Example VI. H2S gas was continu tial was held noble to control hydrogen absorption by 35 ously blown into the three NaCl solutions 5 at 40 C. an electrochemical reaction. The result is shown in FIG. 4. As apparent from FIG. 4, corrosion potential is main EXAMPLE V tained noble with V2O5 and MoC)3, but not with MnO2. This example illustrates the reactivity between vari It is indicated that MnO2 is rapidly changed by reacting ous oxides and H2S. with H2S. A particular amount of V2O5 was put in a petri dish and placed in an atmosphere containing a H2S gas satu EXAMPLE VIII rated with water, for 500 hours. The saturated H2S gas Coating compositions were made and coated on steel was introduced by blowing H2S gas into water at 30 C. panels as generally described in Example VII. Reaction and collecting the bubbled gas. The reacted V2O5 with current to extract the permeated hydrogen was mea H2S was then dried in vacuum and weighed. The 45 sured as generally described in Example 1. The result is weight increase was obtained in terms of percentage by shown in FIG. 5. weight and shown in Table 4 hereinafter. As apparent from FIG. 5, the rise up time of the MoO3, electrolytic MnO2, 3-MnO2 and TiO2 were reaction current curve for MoC)3 and V2O5 is longer treated as mentioned above and the results are shown in than that of MnO2. Though the rise up time of the reac Table 4. 50 tion current curve of MnO2 does not correspond to the shift to be less noble of corrosion potential, it can be EXAMPLE VI understood as follows: MnO2 prevents absorption of This example illustrates the change of corrosion po hydrogen by a similar mechanism to MoC)3 and V2O5 up tential (Ecorr) in respect to a steel panel coated with an to 100 hours and after 100 hours the control of hydro agar gel containing the oxides mentioned in Example V. 55 gen absorption is probably carried out by a different The measurement was carried out using an apparatus mechanism which has been unknown. This mechanism shown in FIG. 3. In FIG. 3, a steel panel 2 was posi does not work sufficiently after 500 hours. It has thus tioned on a substrate 1 and an agar gel containing V2O5 been found that MoC)3 and V2O5 are superior to MnO2. at 5% by weight was coated on the steel panel 2 to form What is claimed is: an agar layer 3. A 3% NaCl solution 5 was poured in an 1. A method for controlling hydrogen absorption of electrolysis cell 4 as a typical corrosion condition to steel which consists essentially of directly coating the allow to polarization. The agar gel 3 was connected to surface of said steel with a composition containing resin an Ag-AgCl reference electrode 9 immersed in 3.33N solids and a metal oxide, with said metal oxide being KCl solution 8 in a glass container 7 through a salt selected from the group consisting of vanadium pentox bridge (3.33N solution gelled with agar) in a rugin tube 65 ide and molybdenum trioxide and being employed at 1 6. The Ag-AgCl reference electrode 9 was connected to to 500 percent by weight, based on 100 percent by a potentiostat. The steel panel 2 was also connected to weight of said resin solids. the potentiostat, of which a C terminal was connected k it k