UNIVERSITÀ POLITECNICA DELLE MARCHE
Dipartimento di Scienze e Ingegneria della Materia, dell’Ambiente
ed Urbanistica
Facoltà di Ingegneria, ANCONA (ITALY)
Prevention and control of corrosion
phenomena directed to extend
components and structures durability
Dr. Tiziano Bellezze
ROUND TABLE RUSSIA ↔ ITALY
Chemical Technologies : Perspectives of development
June 4th -7th 2012
Ivanovo State University of Chemistry and Technology, Ivanovo, RUSSIA
THE CORROSION PHENOMENON
“Corrosion has been the subject of scientific study for more
than 150 years. It is a naturally occurring phenomenon
commonly defined as the deterioration of a material (usually
a metal) or its properties because of a reaction with its
environment.”
World Corrosion Organization (2009)
ABOUT THE ENVIRONMENT… (“the enemy”)
marine environment
industrial environment
urban environment
ABOUT THE ENVIRONMENT… (impact, preservation…)
Accumulation of waste materials
automotive scraps
appliance scraps
Risks of pollution and environmental disasters
pipelines failure
tank failure
CONCERNS WITH HUMAN HELTH AND LIFE
Realise of metals produced by corrosion phenomena
tap water
natural water
cooking pot
Accidents due to corrosion
collapse of ceiling in a swimming pool,
Zurich 1985
bridge collapse
in Minneapolis
on August 1,
2007
THE CORROSION IMPACT ON ECONOMY
“Corrosion has a huge economic and environmental impact
on virtually all facets of the world’s infrastructure, from
highways, bridges, and buildings to oil and gas, chemical
processing, and water and wastewater systems.”
World Corrosion Organization (2009)
US estimated costs of corrosion (nace.org)
Infrastructure
B$
22.6
Utilities
B$
47.9
Transportation
B$
29.7
Production & Manufacturing
B$
17.6
Government
B$
20.1
B$
137.9
TOTAL
ANNUAL COST OF CORROSION WORLDWIDE IS ESTIMATED $US 2.2 TRILLION
THE CORROSION OF STEEL
cathodic reaction
O2 + 2H2O + 4e-
4OHwater media
O2
O2
OHOHOHFe(OH)2 Fe++
Fe(OH)2
Fe++
e- e-
e- e-
anodic reaction
Fe
Fe++ + 2e-
OH-
steel
STRATEGIES FOR CORROSION PREVENTION AND CONTROL
• Materials development and selection
• Analysis and optimization of industrial processes
• Innovative surface protection systems
• Monitoring methods using sensors and remote data
collection
• Development of electrochemical methods/new
analytical
methods
for
studying
corrosion
phenomena
• Education, training courses
• ...
TO INCREASE STRUCTURES AND COMPONENTS DURABILITY
MATERIALS DEVELOPMENT AND
SELECTION
AND
ANALYSIS AND OPTIMIZATION
OF INDUSTRIAL PROCESSES
SCHEME OF A DOMESTIC BOILER
EXAMPLES OF LOCALIZED CORROSION
IN STAINLESS STEEL WATER TANKS
INTERNAL SURFACE PASSIVATION OF THE WATER TANKS
HF + HNO3
solution
AISI 304L, AISI 316L e AISI 444
chemical composition
Alloy
AISI 304L
AISI 316L
AISI 444
Ni
(%)
9.23
11.38
0.27
Cr
(%)
18.29
16.97
18.12
Mo
(%)
0.20
2.28
1.98
Cu
(%)
0.37
0.34
0.07
Ti
(%)
0.02
0.22
C
(%)
0.03
0.03
0.03
18.9
Mn
(%)
2.00
1.95
0.57
Si
(%)
0.55
0.45
0.45
AISI 304L
PRE = % Cr + 3.3 x %Mo
24.5 AISI 316L
Pitting Resistance Equivalent
24.6 AISI 444
Increasing localized
corrosion resistance
SURFACE ASPECT OF STAINLESS STEEL (AS RECEIVED) – F1
AISI 304L
AISI 444
AISI 316L
SURFACE ASPECT OF STAINLESS STEEL AFTER PASSIVATION
AISI 304L
AISI 316L
AISI 444
Surface finishing F4
HF 3% HNO3 13%, r.t., 45’
Surface finishing F8
F4 + HNO3 30%, r.t., 30’
EXPERIMENTAL RESULTS OBTAINED WITH TW1
F4
Potential vs SCE (V)
F1
F8
HF+HNO3
HF+HNO3
HNO3
TW1: [Cl-]=132.8 ppm
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
F1
F4
F8
AISI 304
Perfect passivity region
F1
F4
F8
AISI 316
Surface Finishing
F1
F4
F8
AISI 444
Imperfect passivity region
T. Bellezze, G. Roventi, A. Quaranta and R. Fratesi, Materials and Corrosion 2008, 59 (9), 727-731
INNOVATIVE SURFACE
PROTECTION SYSTEMS
SURFACE PROTECTION SYSTEMS: ZINC COATINGS ON STEEL
car
reinforcing bars
pylon
cathodic reaction: O2 +2 H2O + 4e-  4OHwater media
O2
Zn++
Zn ++
zinc
OH- OH-
steel
e-
e-
anodic reaction: Zn
e-
eZn++ + 2e-
The zinc coating offers:
- barrier effect
- sealing effect
- cathodic protection
- recyclability
- lower costs with
respect to other
coating solutions
DIFFERENT METHODS TO OBTAIN ZINC COATINGS ON STEEL
electrochemical deposition
hot-dip galvanizing
10 m
100 m
 (100% Zn)
 (94% Zn; 6% Fe)
 (90% Zn; 10% Fe)
 (75% Zn; 15% Fe)
FURTHER PROTECTION OF ELECTRODEPOSITED ZINC:
ZINC COATING PASSIVATION
“chromating”
CONVERSION LAYER
Use of Cr VI containing baths:
Cr2O72- + 14 H+ + 6e- → 2Cr3+ + 7 H2O
ZINC
2H+ + 2e- → H2
Zn → Zn2+
STEEL
self-healing effect
local damage
ZINC
STEEL
CONVERSION
LAYER
Cr VI CONVERSION LAYER (CHROMATING)
Cr VI=
1 μm
Directive EU End of Life Vehicles 2000/53/EC:
• Annex II: Cr VI maximum 2 g per vehicle from 1 July 2003
• Amendment Annex II 2002/525/EC : 0 g from 1 July 2007 for
corrosion preventive coatings
POSSIBLE ALTERNATIVES TO THE USE OF Cr VI
• Other oxidant agents similar to chromates: molybdates,
vanadates and permanganetes;
• Ce III and Ce IV salts;
• Cr III (content of Cr VI reduced more than 100 times) with and
without sealants based on Si and some organic compounds
(directed to improve the barrier effect); furthermore, after
drying, Cr III + sealant conversion coating has the possibility of
self-healing effect (migration of silicates present in the sealant);
• Organic compounds producing metal-organic films (ex. Si
compounds);
•…
• Use of Cr VI-free conversion layer on zinc alloys (Zn-Ni, ZnFe,…)
•…
• New strategy: nanocontainers for corrosion inhibitors, released
“on demand”;
•…
NANOCONTAINERS FOR CORROSION INHIBITORS
M. G. S. Ferreira et. al., Chem. Mater. 2007, 19, 402-411
OUR WORK ON THE ALTERNATIVES TO THE USE OF Cr VI
Cr III conversion layer
Cr III + sealant conversion layer
2 μm
5 μm
Investigations performed using the following techniques:
• Electrochemical Impedance Spectroscopy (EIS) in NaCl 5%
• Anodic polarization in NaCl 5%
• Salt fog spray exposure (ASTM B 117)
Results: the Cr III + sealant conversion layer showed a corrosion resistance
comparable with Cr VI conversion layer
T. Bellezze, G. Roventi, R. Fratesi , Surface and Coatings Technology 155 (2002) 221–230
ALTERNATIVES TO CHROMIUM PLATING
The Cr electrodeposition is performed
by Cr VI containing baths
• decorative chromium plating
• hard chromium plating
microhardness
Recently, in our research group, an attempt to substitute the chromium coating with a
composite zinc coating containing nanoparticles (60 nm) of SiC was done. This
coating is particularly indicated in those applications where high hardness is not
necessary.
EDX map of SiC (about 2%)
distribution on zinc coating
pulsed current
MONITORING METHODS
USING SENSORS
AND
NEW APPROCHES IN
CORROSION STUDIES
MONITORING REINFORCING CORROSION IN
CONCRETE WITH THE RISK OF CARBONATION
H2O
concrete
CO2
CO2
pH decreases
steel bar
core
sampling
MONITORING THE CARBONATION DEPTH
MultiProbe A
MultiProbe B
Ti ref.
CO2
CO2
Inside carbonation chamber
the cast
MONITORING THE CARBONATION DEPTH WITH
MULTIPROBE B
250
TiB1
TiB2
TiB3
TiB4
TiB5
225
200
Potential vs TiBrif (mV)
175
150
125
100
75
50
25
0
-25
-50
60
70
80
90
100
110
Time from the cast (days)
120
130
140
150
MONITORING THE CARBONATION DEPTH
multiprobes response vs colourimetric test
POSSIBILITY OF MONITORING OTHER
CORROSION PARAMETERS
•Chlorides penetration depth
•Humidity of concrete matrix (as a function of
depth)
•Corrosion potential
•Corrosion rate
•Aggressiveness of the concrete matrix
•etc.
“MULTIPROBES BOX”
CONCLUSIONS
• Corrosion phenomena have many social, economic and
health implications on human life.
• For new technological challenges, a cultural training on
materials and their degradation is fundamental, both in
industrial R&D and in the university research centres.
• Efforts on the monitoring strategies and on the development
of new devices and/or new sensors should become a
standard practice.
• At the same time, corrosion experts have concluded that a
net of 20 to 25% of that annual cost can be saved by
applying currently available corrosion control technologies.
(WCO, 2009)