{"created":"2025-06-12T01:18:25.716020+00:00","id":2000347,"links":{},"metadata":{"_buckets":{"deposit":"0bb35e2c-69c3-4758-a8a7-0b9093b251a4"},"_deposit":{"created_by":20,"id":"2000347","owner":"20","owners":[20],"pid":{"revision_id":0,"type":"depid","value":"2000347"},"status":"published"},"_oai":{"id":"oai:muroran-it.repo.nii.ac.jp:02000347","sets":["41:227"]},"author_link":[],"item_1716854901627":{"attribute_name":"日付","attribute_value_mlt":[{"subitem_date_issued_datetime":"2026-04-01","subitem_date_issued_type":"Available"}]},"item_81_date_granted_17":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2025-03-24"}]},"item_81_degree_grantor_10":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_language":"ja","subitem_degreegrantor_name":"室蘭工業大学"},{"subitem_degreegrantor_language":"en","subitem_degreegrantor_name":"Muroran Institute of Technology"}],"subitem_degreegrantor_identifier":[{"subitem_degreegrantor_identifier_name":"10103","subitem_degreegrantor_identifier_scheme":"kakenhi"}]}]},"item_81_degree_name_11":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士（工学）","subitem_degreename_language":"ja"}]},"item_81_description_7":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"暖房・換気・空調（HVAC）システムは、通常「蟻の巣腐食」として知られる局部腐食による\n銅管の漏れが原因で、早期に故障する場合がある。この現象の背後にある複雑なプロセスは\n未解明のままであり、著者は以下の研究を行った。(1) 蟻の巣腐食メカニズムに対するリン\nの影響、 (2) ナノX 線CT 検査による無酸素銅管における蟻の巣腐食の複雑な形態の解明、\n(3) ギ酸と酢酸による銅管の腐食挙動の比較。これらをまとめると以下のようになる：\n1. 蟻の巣腐食は、HVAC 産業におけるリン脱酸銅管特有の早期故障である。本研究では、\n無酸素銅管(P 0%)、リン脱酸銅管(P 0.02%)、リンを0.21%および0.29%添加した銅管\nを10􀬷 ppm HCOOH 水溶液に80 日間浸漬し、蟻の巣腐食に対するリンの影響を調査する\nことを目的とした。顕微鏡で観察したところ、60 日間浸漬した銅管の表面はすべて\n紫、オレンジ色から紫、灰色/茶色に変化しており、酸化還元反応による残留固形物の\n生成を示しており、XRD ではCu􀬶O 層と同定された。FESEM/EDX を用いると、無酸素銅\n管では、リン脱酸銅管（P 0.02%）よりも多くの分岐トンネルが見つかり、銅壁内部に\nはCu とO のみが存在した。0.21%と0.29%のリンを添加した銅管では、複数の微細孔腐\n食が発生した。MP-AES の結果、P 0%の試料は銅管（P 0.02%）よりもCu 濃度の平均値\nが低く、酸塩基反応が初期段階の腐食に関与していることがわかった。その結果、銅\n管へのリンの添加は、蟻の巣腐食の進行促進に影響を及ぼさないことが示された。電\n気化学分析により、腐食の初期段階でHCOOH 溶液に浸漬した銅管にリンが急速に溶解\nし、蟻の巣腐食メカニズムのアノード反応中に酸素が著しく消費されることが示され\nた。したがって、蟻の巣腐食は、水分、酸素、ギ酸を同時に必要とする高純度銅管で\n起こりうると結論づけることができる。\n2. 「蟻の巣腐食」と呼ばれる珍しいタイプの腐食が、熱交換器に使われる銅管で確認さ\nれ、早期故障につながるケースがある。この腐食の特徴は、断面分析で観察された、\nアリの巣のような微細な連結トンネルに似た複雑な形態学的パターンであった。しか\nし、腐食プロセスに関与する溶存酸素の正確な経路は、断面観察からは依然として不\n明である。本研究では、無酸素銅管􁈺10.99 cm􀬶􁈻をギ酸およびギ酸銅（II）溶液（濃度\n10、100、1000 ppm）にそれぞれ80 日間浸漬した。光学顕微鏡により蟻の巣腐食が観\n察され、100ppm のギ酸、100 および1000ppm のギ酸銅（II）溶液に浸した銅管ではっ\nきりと確認できた。ギ酸の平均腐食速度は、10ppm で1.2 􀵈 10􀬿􀬷 􁈺nm/s􁈻、100ppm で\n1.9 􀵈 10􀬿􀬷 􁈺nm/s􁈻、1000ppm で0.6 􀵈 10􀬿􀬶 􁈺nm/s􁈻であった。ギ酸銅(II)は、10ppm で\n1.4 􀵈 10􀬿􀬸 􁈺nm/s􁈻、100ppm で8.1 􀵈 10􀬿􀬸 􁈺nm/s􁈻、1000ppm で1.3 􀵈 10􀬿􀬶 􁈺nm/s􁈻であっ\nた。SEM 観察の結果、枝分かれしたトンネルの壁が酸化皮膜で覆われていることが明ら\nかになり、EPMA の結果、酸素と銅元素が主成分であることが確認された。さらに、ナ\nノX 線コンピュータ断層撮影法（CT）により、腐食は銅表面から始まり、枝分かれし\nたトンネルによって特徴づけられる局所的な腐食へと進行し、その後壁を貫通するこ\nとが示された。\n3. カルボン酸、特にギ酸と酢酸は、「蟻の巣腐食 」として知られる局部腐食による暖\n房、換気、空調システムの早期故障に関係している。この研究では、異なる濃度（5、\n10、50、100ppm）のギ酸および酢酸に20、40、60、80 日間暴露した無酸素銅管の腐食\n挙動を調査した。比較調査の結果、それぞれの酸が銅の腐食に与える影響に大きな違\nいがあることがわかった。その結果、ギ酸は酢酸よりも銅管の平均重量損失を大きく\nし、腐食の影響がより強いことが示された。ギ酸にさらされた銅サンプルは、より広\n範囲に表面腐食を示し、どちらの酸も銅表面に結晶性の腐食生成物を形成すること\nが、表面分析から判明した。X 線回折（XRD）研究から、ギ酸腐食の結晶性生成物は酸\n化第一銅􁈺Cu􀬶O􁈻と水酸化ギ酸銅であり、酢酸暴露では酸化第一銅􁈺Cu􀬶O􁈻と水酸化酢酸\n銅が生成されることが明らかになった。断面調査の結果、酸によって腐食形態に大き\nな違いがあることがわかった。ギ酸は複雑に入り組んだ「蟻の巣」のような腐食構造\nを作るのに対し、酢酸は銅の表面に浅いピットを形成することがほとんどである。","subitem_description_language":"ja","subitem_description_type":"Abstract"},{"subitem_description":"The heating, ventilation, and air conditioning (HVAC) systems failed prematurely\ndue to leaks in copper tubes caused by localized corrosion, usually known as “antnest\ncorrosion.” The complex processes behind this phenomenon remain unexplained,\nmotivating the author to conduct the following studies: (1) Effect of phosphorus\non the ant-nest corrosion mechanism; (2) Unveiling the complex morphology of antnest\ncorrosion in oxygen-free copper tubes through nano X-ray CT examination; and\n(3) A comparison of the corrosion behavior of copper tubes induced by formic acid\nand acetic acid. All may be summarized as follows:\n1. Ant-nest corrosion is a unique premature failure of phosphorus-deoxidized\ncopper tubes in the HVAC industry. This study aimed to investigate the\neffect of phosphorus on ant-nest corrosion by immersing oxygen-free copper\ntube (P 0%), phosphorus-deoxidized copper tubes (P 0.02%), and copper tubes\nwith 0.21% and 0.29% phosphorus in 10􀬷 ppm HCOOH solutions for 80 days.\nUnder microscopic examination, the surfaces of all the copper tubes changed\nfrom purple, orange to purple, gray/brown after immersion for 60 days,\nindicating residual solid formation caused by redox reactions, identified\nas the Cu􀬶O layer by XRD. Using FESEM/EDX, more branched tunnels were found\nin oxygen-free copper tubes than in the phosphorus-deoxidized copper tubes\n(P 0.02%), where only Cu and O were present inside the copper wall. Copper\ntubes with 0.21% and 0.29% phosphorus suffered several micro-pitting\ncorrosions. MP-AES results showed that P 0% samples had a lower mean of Cu\nconcentration than copper tubes (P 0.02%), and acid-base reactions played\na role in early-stage corrosion. The results showed that the addition of a\nphosphorus solid to the copper tube had no effect on the accelerated\nprogression of ant-nest corrosion. Electrochemical analysis demonstrated\nthat phosphorus was rapidly dissolved in the copper tubes upon immersion in\nthe HCOOH solution during the early-stage of corrosion, leading to\nsignificant consumption of oxygen during the anodic reaction of the antnest\ncorrosion mechanism. Therefore, it can be concluded that ant-nest\ncorrosion can occur on high-purity copper tubes, which require moisture,\noxygen, and formic acid simultaneously.\n2. An unusual type of corrosion, referred to as “ant-nest corrosion”, was\nidentified in copper tubes used in heat exchangers, leading to premature\nfailure. This corrosion was characterized by intricate morphological\npatterns resembling microscopic interconnecting tunnels observed in crosssectional\nanalyses, like an ant’s nest. However, the exact pathways of\ndissolved oxygen involved in corrosion process remain unclear based on\ncross-sectional observations, likely due to the preparation of methods,\nsuch as cutting and polishing, used before examination. In this study,\noxygen-free copper tubes 􁈺10.99 cm􀬶􁈻 were immersed in formic acid and copper\n(II) formate solutions (concentrations of 10, 100, and 1000 ppm) for 80\ndays, respectively. LOM showed ant-nest corrosion, which was clearly visible\nin copper tubes immersed in 100 ppm formic acid and 100 and 1000 ppm copper\n(II) formate solution. The mean corrosion rates for formic acid were\n1.2 􀵈 10􀬿􀬷 􁈺nm/s􁈻 at 10 ppm, 1.9 􀵈 10􀬿􀬷 􁈺nm/s􁈻 at 100 ppm, and 0.6 􀵈 10􀬿􀬶 􁈺nm/\ns􁈻 at 1000 ppm. Copper (II) formate showed rates of 1.4 􀵈 10􀬿􀬸 􁈺nm/s􁈻 at 10\nppm, 8.1 􀵈 10􀬿􀬸 􁈺nm/s􁈻 at 100 ppm, and 1.3 􀵈 10􀬿􀬶 􁈺nm/s􁈻 at 1000 ppm. SEM\nrevealed that the branching tunnel walls were coated with an oxide layer,\nwhich EPMA confirmed to be primarily composed of oxygen and copper elements.\nFurthermore, nano X-ray computed tomography (CT) indicated that corrosion\ninitiates on the copper surface and progresses to localized corrosion\ncharacterized by branching tunnels that subsequently penetrate the wall.\n3. Carboxylic acids, particularly formic and acetic acids, have been related\nto the premature failure of heating, ventilation, and air-conditioning\nsystems due to localized corrosion known as “ant-nest corrosion.” This\nstudy investigates the corrosion behavior of oxygen-free copper tubes\nsubjected to different concentrations (5, 10, 50, and 100 ppm) of formic\nacid and acetic acid for 20, 40, 60, and 80 days. The comparison\ninvestigation shows significant variations in how each acid affects copper\ncorrosion. The results show that formic acid causes a larger average weight\nloss in copper tubes than acetic acid, indicating a more aggressive\ncorrosive impact. Surface examinations back up this claim, since copper\nsamples exposed to formic acid exhibit more extensive surface corrosion,\nwith both acids forming crystalline corrosion products on the copper surface.\nX-ray diffraction (XRD) study revealed that the crystalline products of\nformic acid corrosion are cuprous oxide 􁈺Cu􀬶O􁈻 and copper formate hydroxide,\nwhereas acetic acid exposure produces cuprous oxide 􁈺Cu􀬶O􁈻 and copper\nacetate hydroxide. Cross-sectional research reveals a significant variation\nin corrosion morphology between the acids: formic acid creates intricate,\ndeeply penetrating \"ant-nest\" corrosion structures, whereas acetic acid\nmostly forms shallow pits on the copper surface.","subitem_description_language":"en","subitem_description_type":"Abstract"}]},"item_81_dissertation_number_13":{"attribute_name":"学位授与番号","attribute_value_mlt":[{"subitem_dissertationnumber":"甲第551号"}]},"item_81_text_12":{"attribute_name":"学位の種別","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"課程博士"}]},"item_81_text_14":{"attribute_name":"報告番号","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"甲第551号"}]},"item_81_text_15":{"attribute_name":"学位記番号","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"博甲第551号"}]},"item_81_text_16":{"attribute_name":"研究科・専攻","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"工学研究科"}]},"item_81_version_type_24":{"attribute_name":"著者版フラグ","attribute_value_mlt":[{"subitem_version_resource":"http://purl.org/coar/version/c_970fb48d4fbd8a85","subitem_version_type":"VoR"}]},"item_access_right":{"attribute_name":"アクセス権","attribute_value_mlt":[{"subitem_access_right":"embargoed access","subitem_access_right_uri":"http://purl.org/coar/access_right/c_f1cf"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorAffiliations":[{"affiliationNames":[{"affiliationName":"室蘭工業大学","affiliationNameLang":"ja"},{"affiliationName":"Muroran Institute of Technology","affiliationNameLang":"en"}]}],"creatorNames":[{"creatorName":"TAMBANG, MANIK","creatorNameLang":"en"}],"familyNames":[{"familyName":"TAMBANG","familyNameLang":"en"}],"givenNames":[{"givenName":"MANIK","givenNameLang":"en"}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2026-04-01"}],"filename":"A551.pdf","filesize":[{"value":"18.4 MB"}],"format":"application/pdf","url":{"objectType":"fulltext","url":"https://muroran-it.repo.nii.ac.jp/record/2000347/files/A551.pdf"},"version_id":"0b680ccb-1fdd-401a-85cb-6c7b6008e595"},{"accessrole":"open_access","date":[{"dateType":"Available","dateValue":"2025-06-12"}],"filename":"A551_summary.pdf","filesize":[{"value":"191 KB"}],"format":"application/pdf","url":{"objectType":"abstract","url":"https://muroran-it.repo.nii.ac.jp/record/2000347/files/A551_summary.pdf"},"version_id":"2b28cfb1-b05c-4ee4-a809-7f43a71db103"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"doctoral thesis","resourceuri":"http://purl.org/coar/resource_type/c_db06"}]},"item_title":"A Study on Ant-Nest Corrosion of Copper Tubes Occurring in Carboxylic Acid and Carboxylate Environments","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"A Study on Ant-Nest Corrosion of Copper Tubes Occurring in Carboxylic Acid and Carboxylate Environments","subitem_title_language":"en"},{"subitem_title":"カルボン酸およびカルボン酸塩環境下で発生する銅管の蟻の巣状腐 食に関する研究","subitem_title_language":"ja"}]},"item_type_id":"81","owner":"20","path":["227"],"pubdate":{"attribute_name":"PubDate","attribute_value":"2025-06-12"},"publish_date":"2025-06-12","publish_status":"0","recid":"2000347","relation_version_is_last":true,"title":["A Study on Ant-Nest Corrosion of Copper Tubes Occurring in Carboxylic Acid and Carboxylate Environments"],"weko_creator_id":"20","weko_shared_id":-1},"updated":"2025-06-12T01:24:53.161855+00:00"}