Fiber Corrosion Research Articles

Optical fibre sensors for monitoring ageing of materials: Application to polyethylene and metallic structures

Two examples of in situ monitoring of ageing of materials with optical fibres are shown in this paper: thermal degradation of polyethylene and corrosion in aeronautic structures (aluminium) with an optical fibre corrosion sensor (OFCS).The thermal degradation of polyethylene is monitored by inclusion of an uncladded optical fibre in the polymer. Through modelling of the angle distribution of the normalized light power transmitted with geometric optics, the refractive index of the polymer is determined at different temperatures (n=1.4594 - i0.0007 at 28°C and n=1.5162 - i0.0007 at 120°C). The variation of the refractive index is related to a variation of crystallinity of the polymer. The kinetics of degradation was directly followed at different temperatures.The OFCS is tested by two methods: optical and electrochemical methods for different aluminum thickness deposited on the sensitive part of the optical fibre, in different acid concentration. The mechanisms of corrosion (uniform or in preferential places) can be deduced from the optical signal. The sensitivity of the OFCS is good for the low thickness. Corrosion rates for aluminum and copper are quite different, the effect of oxide layer on aluminum is important and induces corrosion in several stages.

Corrosion of steel fibre reinforced concrete from the cracks

The corrosion of steel fibres in the cracked section has been under investigation by many researchers since the last 15 years. It is reported widely that in case of steel fibres reinforced concrete (SFRC), corrosion is less active as compared with steel bars. In the cracked section, the durability of the material depends on the performance of the bridging capacity of the fibres embedded in the concrete. The corrosion of the fibres not only could produce the spalling of concrete but it could also reduce the sectional area of the fibres, turning the durability of structures in danger. This study focuses on those two aspects of fibre corrosion. The tests were performed on cracked SFRC samples with 0.5-mm crack mouth openings (CMOs) exposed to marine-like environment for 1 year. The results confirm the small sensitivity of SFRC to corrosion. Surprisingly, they made appear an increase of the flexural strength after corrosion. The factors affecting the corrosion of the fibres and the reasons for the increase in flexural strength after corrosion are discussed.

Elaboration of an optical fibre corrosion sensor for aircraft applications

As the fleet of both civilian and military aircraft ages, the need for understanding the effects of corrosion becomes increasingly important. So, our goal is to develop an optical fibre corrosion sensors (OFCS), fabricated by thermal deposition of an aluminium film onto an optical fibre core within the sensing region in order to follow corrosion in aeronautic structures. The OFCS is tested by two methods: optical and electrochemical methods for different aluminium thickness deposited, in different acid concentration. The mechanisms of corrosion (uniform or in preferential places) can be deduced from the optical signal. The sensitivity of the OFCS is good for the low thickness. Corrosion rates for aluminium and copper are quite different, the effect of oxide layer on aluminium is important and induces corrosion in several stages.

Elaboration and standardization of an optical fibre corrosion sensor based on an electroless deposit of copper

The goal of our present work is to develop and test an optical fibre corrosion sensor (OFCS) fabricated by an electroless copper film deposition onto an optical fibre core within the sensing region. In our case, corrosion monitoring was carried out by two methods: optical and electrochemical methods. The idea consists is to couple these two methods by correlating the parameters describing the optical detection and those which describe the electrochemical corrosion process. This approach, once is carried out, makes it possible to gain more precise information on degradation within hidden parts of metallic structures.

An optical fibre corrosion sensor with an electroless deposit of Ni–P

The feasibility of an optical fibre corrosion sensor (OFCS) is studied. A PCS fibre is metallised with chemical nickel–phosphorus deposit on an uncladded part of 2 cm length. The light power ( P) transmitted through the fibre is registered as a function of the angle of incidence ( α) of the light emitted by a laser diode at 670 nm wavelength. The P( α) curves are modified when the nickel coating is corroded in phosphoric acid solutions, the full width of these curves at half-maximum increases when the density of corrosion pits increases. Kinetic curves of the corrosion are determined in different concentrations of phosphoric acid. This type of corrosion sensor can be inserted in structures in order to follow in situ the corrosion state of the structure.

1735 酸応力環境下における GFRP 織物積層板のき裂進展特性 : 耐食性 FRP の下限界特性

Objective of this study is to clarify the crack-propagation properties of corrosion resistant GFRP laminates under various acid stress environments, an effect of the constituents on fracture and the threshold properties of the crack propagation. This experiment was performed under constant loading in HCl solution and the crack propagation behavior was depicted on a K_1-da/dt diagram. The fracture surfaces of the specimens were observed by scanning electron microscope. As the acid concentration increased the crack propagation was accelerated, however, the effect of the acid concentration was not so dominant. The crack propagation behavior in the water was largely enhanced in comparison with that in the air and it was nearly as promoted as that in the acid solution. Therefore it was noted that the failure of the C/VE systems was occurred by not fiber corrosion but absorption and swelling derived from the diffusion of the water into the matrix and a changing of the stress shearing on the fibers at crack tip.

Corrosion of E-glass fibers in acidic environments

This study is concerned with the corrosion behavior of E-glass fibers exposed to oxalic, hydrochloric, nitric and sulfuric acids. The results reveal that acid corrosion of E-glass fibers is primarily attributed to calcium and aluminum ion depletion. The leachability of these metallic ions is not only determined by the hydrogen ion concentration but also strongly affected by the anions in the acids. The formation of insoluble salts or complex ions between the anions in oxalic and sulfuric acids and calcium and aluminum ions leached out from the glass accelerates fiber corrosion considerably. Furthermore, acid corrosion may generate axial or spiral cracks on the fiber surface, depending on acid type and concentration. In this study, an ion-depletion-depth model is proposed to explain the mechanisms of fiber surface cracking; the axial crack formation is most likely associated with a larger ion-depletion depth than the spiral crack formation.

New sol-gel matrices of chemically stable composites of BAS, NAS and CAS

The preparation of ceramic-matrix composites made with celsian (BAS), anorthite (CAS), and amorphous albite (NAS) matrices and reinforced with Nicalon ® NLM202 SiC woven fibers is reported. The method used to make composites is a three stage sol-gel process: (i) in situ gelation of a mixture of alkoxides in a ceramic fibre fabric; (ii) deposit of a matrix precursor onto the impregnated fabrics; and (iii) hot-pressing. Emphasis is given to the preparation of a single-step-firing matrix powder leading to dense composites. Three-point flexural strengths have been determined. The matrix and fibre corrosion by proton or sodium ions is discussed. The BAS matrix presents a good compromise between chemical, mechanical and manufacturing criteria.

Influence of Polymer Coatings and Adhesion on the Mechanical Strength, Fatigue and Aging of Optical Fibers

AbstractThe influence of polymer coatings on the mechanical properties of optical fibers is reviewed. Current research is directed at the chemical mechanisms that contribute to mechanical strength degradation. In this review, a chemical kinetics model is applied to describe the influence of polymer adhesion on chemical corrosion of the glass fiber (i.e., its zero stress and stress assisted corrosion).

Scanning Tunneling Microscopy of Optical Fiber Corrosion: Surface Roughness Contribution to Zero‐Stress Aging

Strength, fatigue resistance, and zero‐stress aging behavior control the long‐term mechanical reliability of optical fibers. Zero‐stress aging refers to the loss of strength of high‐strength glass fibers after exposure to some corrosive environments in the absence of stress. Understanding the effect of the chemical environment under zero stress on the subsequent fracture strength of optical fibers is important because optical fibers in service will probably encounter water and other chemical species while exposed to zero‐ or low‐stress conditions. In this work, the strength of fibers aged under zero‐stress conditions at 80°C in deionized water has been measured. Scanning tunneling microscopy was also used to measure the roughening of the fibers from corrosion at intervals during the aging. The product of the median inert strength of fibers aged for various times and the square root of the roughness depth of fibers was constant within experimental error. The results show that surface roughening contributes to zero‐stress aging in silica fibers.

Corrosion of Steel Fiber Reinforced Concrete

Corrosion of Steel Fiber Reinforced Concrete

Anodic Corrosion of Fiber Reinforced Lead Composites for Use in Large Lead‐Acid Batteries

The corrosion resistance of lightweight, high strength lead metal matrix composites under conditions that simulate their use as grid materials in large lead‐acid batteries has been studied. Constant potential testing provides an effective means for holding constant the oxidizing power of a metal‐electrolyte system. Data are presented on corrosion currents, effect of exposure time on corrosion rates, dependence of the rate of corrosion on temperature, and the current flow that is proportional to the rate of corrosion.

Method of producing silaceous fibre corrosion inhibiting composites : Shannon, R. F. (Owens-Corning Fiberglas Corp) US Pat. 3 661 663 (9 May 1972)

Method of producing silaceous fibre corrosion inhibiting composites : Shannon, R. F. (Owens-Corning Fiberglas Corp) US Pat. 3 661 663 (9 May 1972)

Examination of the influence of pretreatment on the corrosion of glass fiber by means of dispersion analysis

Examination of the influence of pretreatment on the corrosion of glass fiber by means of dispersion analysis