B0746 Corrosion of reinforcement in concrete (EFC 31) (matsci)

136 Pages·2000·6.91 MB·English

by  J. Mietz, R. Polder, B. Elsener

European Federation of Corrosion
Publications
NUMBER 31
Corrosion of Reinforcement
in Concrete
Corrosion Mechanisms and
Corrosion Protection
Papersfrom EUROCORR '99
Edited by
J. MIETZR, . POLDER B. ELSENER
AND
Published for the European Federation of Corrosion
by IOM Communications
Book Number 746
Published in 2000 by IOM Communications Ltd
1 Carlton House Terrace, London SWlY 5DB
IOM Communications Ltd
is a wholly-owned subsidiary of
The Institute of Materials
02 000 IOM Communications Ltd
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ISBN 1-86125-133-5
Neither the EFC nor The Institute of Materials
is responsible for any views expressed
in this publication
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Made and printed in Great Britain
Reinforced concrete is such a widely used construction material that in most of the
world the cost of damage and repair is an important issue despite the fact that the
majority of structures are undamaged and have a long service life. In fact, only a small
fraction of the total stock is responsible for most of the problems with reinforcement
corrosion as the main cause. Owners, engineers and researchers are trying to find
solutions to the problems that are involved. Although the most important factors in the
corrosion of reinforcing steel are well known necessary work continues in the
understanding of rate controlling mechanisms, in developing test methods to assess the
severity of existing corrosion and in producing computer based diagnostic systems.
Various methods to protect structures have been applied for many years and new
ideas have been introduced in recent decades. Cathodic protection of reinforcement
is a successful method to stop ongoing corrosion and this application is being
extended to new types of structures, to the use of new materials and to links with
conventional repairs. Other new technologies in the field are the use of stainless steel,
inhibitors and water repellent treatments for improved service life.
This volume in the EFC series brings together the full papers presented in the
successful session ”Corrosion of Steel in Concrete’’ at E UROCORR ’99 held at Aachen,
Germany. Thirteen papers were accepted after peer review, and included contributions
from The Czech Republic, Denmark, Germany, Italy, The Netherlands, Norway,
Poland and Switzerland.
The papers are grouped under two headings:
Corrosion Mechanisms and Corrosion Measurements
Corrosion Protection of Reinforced Concrete Structures
We thank all authors who were willing to share their valuable ,.nowlecge with others
and who participated in discussions. The editors hope these papers will encourage
readers to apply the ideas and results that were presented to their own problems. The
work reported in this volume can be read in conjunction with other EFC publications
from this Working Party, for example:
EFC 18 Stainless Steels in Concrete: State of the Art Report
EFC 24 Electrochemical Rehabilitation Methods for Reinforced Concrete Structures:
State of the Art Report
EFC 25 Corrosion of Reinforcement in Concrete: Monitoring, Prevention and
Rehabilitation
and in conjunction with further volumes in preparation on the subjects of inhibitors
for use in concrete, and embeddable reference electrodes for concrete.
J. MIETZ Chairman of the EFC Working Party on Corrosion in Concrete
R. POLDER
B. ELSENER
European Federation of Corrosion Publications
Series Introduction
The EFC, incorporated in Belgium, was founded in 1955 with the purpose of
promoting European co-operation in the fields of research into corrosion and corrosion
prevention.
Membership is based upon participation by corrosion societies and committees in
technical Working Parties. Member societies appoint delegates to Working Parties,
whose membership is expanded by personal corresponding membership.
The activities of the Working Parties cover corrosion topics associated with
inhibition, education, reinforcement in concrete, microbial effects, hot gases and
combustion products, environment sensitive fracture, marine environments, surface
science, physico-chemical methods of measurement, the nuclear industry, computer
based information systems, the oil and gas industry, the petrochemical industry,
coatings, automotive engineering and cathodic protection. Working Parties on other
topics are established as required.
The Working Parties function invarious ways, e.g.b y preparing reports, organising
symposia, conducting intensive courses and producing instructional material,
including films. The activities of the Working Parties are co-ordinated, through a
Science and Technology Advisory Committee, by the Scientific Secretary.
The administration of the EFC is handled by three Secretariats: DECHEMA e. V.
in Germany, the Sociktk de Chimie Industrielle in France, and The Institute of
Materials in the United Kingdom. These three Secretariats meet at the Board of
Administrators of the EFC. There is an annual General Assembly at which delegates
from all member societies meet to determine and approve EFC policy. News of EFC
activities, forthcoming conferences, courses etc. is published in a range of accredited
corrosion and certain other journals throughout Europe. More detailed descriptions
of activities are given in a Newsletter prepared by the Scientific Secretary.
The output of the EFC takes various forms. Papers on particular topics, for
example, reviews or results of experimental work, may be published in scientific and
technical journals in one or more countries in Europe. Conference proceedings are
often published by the organisation responsible for the conference.
In 1987 the, then, Institute of Metals was appointed as the official EFC publisher.
Although the arrangement is non-exclusive and other routes for publication are still
available, it is expected that the Working Parties of the EFC will use The Institute of
Materials for publication of reports, proceedings etc. wherever possible.
The name of The Institute of Metals was changed to The Institute of Materials with
effect from 1 January 1992.
The EFC Series is now published by the wholly-owned subsidiary of The Institute
of Materials, IOM Communications Ltd.
A. D. Mercer
EFC Series Editor,
The Institute of Materials, London, UK
Vl.lIl. Series Introduction
EFC Secretariats are located at:
Dr B A Rickinson
European Federation of Corrosion, The Institute of Materials, 1 Carlton House
Terrace, London, SWlY 5DB, UK
Mr P Berge
Federation Europeene de la Corrosion, Societe de Chimie Industrielle, 28 rue Saint-
Dominique, F-75007 Paris, FRANCE
Professor Dr G Kreysa
Europaische Foderation Korrosion, DECHEMA e. V., Theodor-Heuss-Allee 25,
D-60486, Frankfurt, GERMANY
Contents
Series Introduction uii
Preface ix
Foreword X
Part I - Corrosion Mechanisms and Corrosion Measurements 1
1. Oxygen Reduction on Mild Steel and Stainless Steel in Alkaline Solutions 3
S. JAGGI, B. ELSENERA ND H. BOHNI
2. Investigations on Cathodic Control of Chloride-Induced Reinforcement 13
Corrosion
M. RAUPACAHN D J. GULIKERS
3. Critical Factors for the Initiation of Rebar Corrosion 25
L. ZIMMERMANB.N E,L SENERAN D H.B OHNI
4. Field Tests of Chloride Penetration into Concrete with Microsilica 35
0. VENNESLAANNDD J. HAVDAHL
5. Comparison of Electrochemical Data and Mass Loss Corrosion Rate 41
Measurements for Steel Reinforcement in Concrete
P. NOVAKA ND R. MALA
Part 2 - Corrosion Protection of Reinforced Concrete Structures 49
6. Corrosion and Protection in Reinforced Concrete: A Computerised 51
System for Studying its Phenomenology, Causes, Diagnosis
and Remedies
P.P EDEFERRI
vi Contents
7. Organic Corrosion Inhibitors for Steel in Concrete 61
B. ELSENERM, . BUCHLERA ND H.B OHNI
8. Corrosion Protection of Reinforcement by Hydrophobic Treatment 73
of Concrete
R. B. POLDERH, . BORS~AEN D J, DE VRIES
9. Cathodic Protection of Concrete Ground Floor Elements with 85
Mixed-in Chloride
G. SCHUTENJ., LEGGEDOOARN D R. B. POLDER
10. Sacrificial Anodes for Cathodic Prevention of Reinforcing Steel 93
Around Patch Repairs Applied to Chloride-Contaminated Concrete
G. SERGAI ND C. L. PAGE
11. Layer Zinc Anodes in Cathodic Protection of Steel Reinforcement 101
W. BOHDANOWICZ
12. Lifetime Extension of Thermally Sprayed Zinc Anodes for 109
Corrosion Protection of Reinforced Concrete Structures by Using
Organic Top-coatings
I. SPRIESTERSBACAH. M, ELZER1., W ISNIEWSKI, A. WINKEALNDS M .K NEPPER
13. Practical and Economical Aspects of Application of Austenitic 121
Stainless Steel, AIS1 316, as Reinforcement in Concrete
0.K LINGHOFFETR., F RaLUND, B. KOFOEDA, . KNUDSENF, .M .J ENSEN
AND T. SKOVSGAARD
List of Abbreviations 135
Index 137
Part 1
Corrosion Mechanisms
and Lorrosion
Measurements
1
Oxygen Reduction on Mild Steel and Stainless
Steel in Alkaline Solutions
S. JAGGI, B. ELSENER and H. BOHNI
Institute of Materials Chemistry and Corrosion, Department of Civil Engineering Swiss Federal Institute of
Technology, ETH Honggerberg, CH-8093 Zurich, Switzerland
ABSTRACT
The cathodic polarisation curve of steel in alkaline solutions always shows three
regions: (1)o xygen reduction with a Tafel behaviour at potentials cathodic to the
open circuit potential followed by (2) a diffusion limited current of oxygen reduction
at more negative potentials and (3) hydrogen evolution at very negative potentials.
The diffusion limited region of the cathodic current density is controlled both by
the oxygen concentration in solution and the flow rate whereas in the Tafel region
(charge transfer) the temperature and the pretreatment of the sample determine
the intensity of the current density and the slope of the Tafel line. On stainless
steels the cathodic reduction currents are lower then on mild steel. It can be
concluded that under usual corrosion conditions for steel in concrete the cathodic
oxygen reduction is not diffusion limited but charge transfer controlled.
1. Introduction
The corrosion reaction, i.e. the anodic dissolution of steel in concrete, has to be
sustained by a corresponding cathodic reaction: in general, this is the reaction of
oxygen with water producing hydroxyl ions:
0, + 2H,O + 4e- -+ 40H- (1)
The availability of oxygen at the steel surface and the reaction kinetics of
oxygen reduction are thus key factors in the corrosion of steel in concrete. Quite
often the reduction of oxygen at the steel surface in alkaline environments is
called diffusion limited although only a few papers report results on kinetics
and mechanism of oxygen reduction on passive iron or steel in alkaline solutions
[1,2]. The influence of oxygen on corrosion of steel in concrete has been studied
[3-51. In this work, the influence of oxygen content, temperature and ageing of
the passive film on the oxygen reduction reaction on normal and stainless steel
in alkaline solutions has been studied. The results are discussed with respect to
the mechanism of oxygen reduction and the importance for corrosion of steel in
concrete.
4 Corrosion of Reinforcement in Concrete: Corrosion Mechanisms and Corrosion Protection
2. Experimental
Potentiodynamic polarisation curves (scan rate 1 mVs-l) were recorded in an
electrochemical flow cell (Fig.1) at defined temperatures and hydrodynamic
conditions. The flow velocity was regulated by the flux of solution, 1 mLs'
corresponds to a flow velocity of ca. 1.4 mms-I. The counter electrode was a platinum
wire spiral and the reference electrode was a saturated calomel electrode. The
materials tested (working electrode) were mild steel and DIN 1.4301 stainless steel
cylinders with a diameter of 8 mm, embedded in resin and mounted in the flow cell.
For each experiment the samples were freshly ground with 180 grit emery paper in
water, cleaned with ethanol in an ultrasonic bath, rinsed with deionised water and
immersed for 24 h in the alkaline test solution open to air to form the passive film.
As electrolytes 0 . 1N~a OH and synthetic pore solution (Table 1) were used. The
temperature (5-47OC), oxygen concentration (open to air or saturated) and flow
velocity (stagnant or 1 mLs-l) were varied; in addition, experiments with prolonged
immersion times (ageing of the passive film up to 4 months) of the samples were
performed.
Fig. 2 Schematic representation of the electrochemical pow-cell that allows the registration of
cathodic polarisation curves under controlled temperature, potential and oxygen content.