別紙4 (課程博士)
Date of submission

平成DepaHment

年

月

福本

臼広Supervisors

松本明彦

指導教員

三浦均也

松本幸大

StudentlD Number

機械工学専攻Pplica11t's name

氏名

学籍番号第 149104 号

星野雅彦

29Ⅱ日Abstract

論文内容の要旨(博士)
港湾環境下におけるぺトロラタム被覆防食材および被覆防食工法
Title ofThesis

博士学位論文名の劣化機構の解明( Elucidation of Deterioration Nlechanism of petrolatum Materials and Lining syst
em in Marine Environment )'モ(Approx.80o words)(要旨 1,200字程度)
港湾鋼構造物の防食法の1つであり,多くの実績があるぺトロラタム被覆防食工法の劣化機構にっいて検討を行った。主材料であるぺトロラタム系防食材(以下、防食材)と F貯保護カバー材(以下、F即)に着目し、それぞれの劣化機構について検討した。また、ペトロラタム被覆防食工法は、鋼材の防食が目的であるため、防食材やF即の劣化が鋼材の腐食に与える影響についても検討した。さらに、現在の維持管理手法の主手法である目視調査の問題点について整理し、安易かつ時間短縮が可能な維持管理手法について提案した。以下に本研究で得られた知見を示す。
①防食材は酸化による低分子量化が主体の劣化を生じ、その劣化は暴露年数が増加するにっれて進行する.劣化は温度による影響が大きいと考えられ,実環境下では直射日光の影響を受けやすい飛沫帯にその傾向が表れやすいことが分かった.また,劣化した防食材は,親水的なカルボニル基を生じるととから,鋼材表面へ水分を供給しやすい原因になることも明らかとなった'ξ毛L②欠陥率測定や電気化学的測定を実施することで実環境下における防食材の劣化と鋼材腐食の関係性を解明した.特に飛沫帯では,温度の影響を受けた防食材が下方へ流動し,不織布の縫い目を起点として防食材に物理的な欠陥を生じ,波浪による水分や気中の酸素といった腐食因子が防食材に生じた欠陥部を起点に鋼材表面へ到達することで腐食することが明らかとなった。
(3) FRPの劣化は,樹脂の酸化と加水分解が主であることが明らかとなった.酸化と加水分解では,加水分解の方が劣化に与える影響は大きく,温度変化よりも水が関与する劣化が機械的強度に与える影響は大きいととが分かった.また、一般的なF即とは異なり紫外線が強度低下に与える影縛は小さかった④ FRPの機械的強度の低下は,表面から内部に向かって徐々に劣化が進行していくことに起因し,その強度の低下は,引張強度よりも曲げ強度に顕著に表れるととが明らかとなった.目視の色調変化程度と機械的強度には明確な関係性はないととが分かった(5)釧材の腐食を意味する工法の劣化は,特に飛沫帯に影響が出やすいことが分かったため、劣化判
断は飛沫帯の防食材および鋼材表面について実施することが望ましい.なお、飛沫帯が健全である場合,干満帯や海水中も健全である可能姓が高い.また、F即は,暴露年数が増加するにつれ表面が劣化し,機械的強度が低下していく傾向があるが,破損や脱落等の異常がない状態であれぱ,釧材腐食には直接大きな影響は与える影響は小さい(6)現在の目視調査主体の維持管理手法は鋼材の防食状態を評価する手法としては問題があるととか

ら、簡易かつ早期の判断が可能な欠陥率による新たな評価手法を提案した。欠陥率測定に用いる防食材の回収位置は飛沫帯とし,測定される欠陥率の閖値を0.2%とすることを提案した

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ξ窒ミ

別紙4 (課程博士)
Date of submission

平成
Depadment

Pplicant's name

氏名

学籍番号

弔 149104 号

Masahiko Hoshino

年月Ⅱ日

Masahiro Fukumoto

S加dentlDNumber

MechanicalEn即neering

29

SupeNisors

Akihiko Matsumoto

指導教員

KinyaMiura
Yukihiro Matsumoto

Abstract

論文内容の要旨(博士)Title ofThesis

Elucidation of Deterioration

博士学位論文名m in Marine Envu'onment

Mechanism of petrolatum Nlaterials and Lining syste(Approx.80o words)ゞ一宅(要旨 1,200字程度)
The deterioration mechal)ism of the pe訂'olatum lining system which is a popular conosion prevention method formarh)e steel stmC加res was invest喰ated. The deterioration mechal)ism ofthe petrolatum material(hencefodh referred

to as " anticonosion material") a11d 6ber・rei11forced plastic (FRP) protective covennateHal(hencefodh refened to as
4FRP") was investi8ated. AdditionaⅡy, since the objective ofthe petrola加m Hning system is the prevention ofthe
Conosion of steel materials, the ea'ect ofthe deterioration ofthe arlticorrosion material arld FRp on the conosion ofSteel materials was also investigated. Fur丘lermore, the drawbacb of visual examination, which is the primaty
maintena11Ce melhod cunenuy used, were analyzed and a new facile arld less time・consuming maintenance method、vas proposed.
The findingS 丘'om this stいdy are summadzed below.

(D The anticonosion material deteriorated mainly by oxidative degradation. The deterioration proceeded as theず長竃

exposure time under practical environment increased. R 、vas found that the temperature a行'ected thedeterioration signi丘Canuy. The deteri01'ation occurred readily in the splash zone, which is susceptible to theea'ect of direct sunlight in a practical envlronment.1t was also revealed that the deterioration of theanticorrosion material supplied moisture to the surface of steel materials, because the deterioration material
Produced hydrophilic carbonyl groups.
(2) The relationshゆ bet、Neen the degradation ofthe anticorrosion material and the corrosion of steel materials
in practical environment was elucidated implementing the defect rate measurement and electrochemicalmeasurement. Especia11y in splash zone, the anticorrosion material was a丘'ected by temperature and aowed
downward, resulting in physical defects in the anticorrosion material originating from the stitches of
nonwoven fabrics.1t was found that the corrosion occurs when the conosion factors, such as moistureOriginating from ocean 、vaves and oxygen in the air, reach the surface ofsteel materials originating 丘om thedefective podion in the anticonosion material.

(3) 1t was revealed that the deterioration of FRp of was mainly due to the oxidation and hydrolysis of thePolyester resin. The deterioration was inauenced more by hydrolysis than by oxidation, and the water・assisted
deterioration of FRp inauenced its mechanical strength more than the temperature・assisted deterioration,
Additiona11y, the ea'ect ofultraviolet light on the strength ofthe FRp material used in this study was sma11er
than on the wpical FRP.

(4) 1t was revealed that the reduction in the mechanical strength of FRp is due to the gradual progress ofthe
deterioration from the surface toward the inside, and the reduction in the strength was more remarkable forbending than for tensile.1t was also found that there 、vas no dear relationship beNeen the degree of c010r
tone change (as obseNed by visual examination)飢d the mechanicalstrength.
(5) 1t was found that the deterioration ofthe lining,、vhich leads to the corrosion ofthe steel materials, tends toinauence the splash zone. Therefore, it is desirable to carry out the investigation of the deterioration
mechanism ofthe anticorrosion material and the surface of steel materials in the splash zone.1fthe structurein the splash zone is robust, the structure in the tidal zone 卸d in the seawater is also likely to be robust.
Although the surface ofFRp has a tendency to deteriorate and its mechanicalstrength decreases according to
the length ofexposure, the cha11Ces ofits deterioration a丘'ecting the conosion ofsteel materials are negligible
in the absence ofany abnonnality such as damage orseparation(6) New evaluation method based on the defect rate a110wing easy and earlier evaluation was proposed.1t was一

also proposed that the c0Ⅱection position of the anticorrosion material to be used for the defect ratemeasurements be located atthe splash zone and the threshold value ofthe defectrate to be measured shaⅡ be
0.2%.

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