PhD. José Javier Gracenea

Electrochemical techniques for the quality control of COR-TEN steel

COR-TEN© E PROTEZIONE ANTICORROSIVA CON PRODOTTI VERNICIANTI: ESPERIENZE A CONFRONTO 7 FEBBRAIO 2013 Orio Al Serio (BG) presso NH Hotel

INTRODUCTION

THE TECHNIQUE

HISTORY CASES

CONCLUSIONS

INTRODUCTION

THE TECHNIQUE

HISTORY CASES

CONCLUSIONS

CORROSION It is an irreversible interfacial reaction of a material (metal, ceramic, polymer) with its environment which results in consumption of the material or in dissolution into the material of a component of the environment.

INDUSTRIAL PROBLEMS:

Human accidents (piece brooking)

Economical Damage: 300.000M€ per year

Study of the corrosion mechanism (avoid or decrease it)

Natural evolution of cor-ten steel

Study and development of the protection mechanism (if the corrosion can´t be avoid, how can we protect

metals). coated cor-ten steel

DEALING WITH THE PROBLEM

• Oxidation Process – anode Fe2+ + 4 Cl- → 2 FeCl2

Fe2+ + 3/2O2 → Fe2O3

• Reduction Process – cathode 2OH- + 2Na+ → 2NaOH 4OH- + Fe2+ → 2 Fe(OH)2

e-

e-

O2 H2O

Cl- Na+

H2O + NaCl

a c

Steel

DELAMINATION

Fe2O3 FeCl2

NaOH Fe(OH)2

Fe2+

OH-

c

NaOH

BLISTER

CORROSION MECHANISM (COATED STEEL )

Typical applications for weathering structural steels : • external wall claddings of buildings, weather strips. • chimneys and other structures under flue gas conditions.

• transport tanks. • freight containers. • bridges. • heat exchangers. • similar other steel structures.

INTRODUCTION

THE TECHNIQUE

HISTORY CASES

CONCLUSIONS

EVALUATE

ACCELERATING

CORRELATING THE NATURE

How?

IMITATING THE NATURE

MIMETIZAR Imitar o reproducir la Naturaleza. SEPARATING FACTORS

MIMETIZAR Imitar o reproducir la Naturaleza.

INTENSIFICATING FACTORS

PREDICTING FAILURE

CONVENTIONAL ACCELERATED TESTS

ASTM G154 ISO 4892-3

STATIC

ISO 20340 NORSOK 501

DYNAMIC

ISO 17872: corrosion in the scribe.

ISO 4628-2: degree of blistering.

ISO 4628-3: degree of rusting.

ISO 4628-4: degree of cracking. ISO 4628-5: degree of flaking.

ISO 4628-10: corrosión filiforme.

VISUAL EVALUATION (NON NUMERICAL)

E (V)

I (A

)

POTENTIODINAMIC STUDIES

CATHODIC ANODIC

EM0/M

IM0/M

E (V)

I (A

)

POTENTIODINAMIC STUDIES

CATHODIC ANODIC

EM0/M

IM0/M

ICORR

ECORR

φ Eoc

I

E

t

Input (Perturbation):

E(t) = E0 + ∆E· sen (ωt)

Output:

I(t) = I0 + ∆I· sen (ωt-φ)

Z =f (freq)

ELECTROCHEMICAL TECHNIQUES (EIS)

Cdl Cc

Rp Rpo

E Z

Development by Jaume I University and in commercially introduced by MEDCO

Based on ACDCAC test (Hollaender, J.) but introduce three improvements

ACCELERATED ELECTROCHEMICAL TECHNIQUES (ACET)

Accelerated Cyclic Electrochemical Technique Suay. JCT, 75, 103-111, (2003).

NUMERICAL EVALUATION (EIS)

EIS

EIS

EXPOSURE

NUMERICAL

CORRELATIONS

Relaxation potential testing

New procedure

of evaluation

results

It establishes correlation

with normalized

tests

ACCELERATED ELECTROCHEMICAL TECHNIQUES (ACET)

(III)

Relaxation time

AC

(IV)

DC

AC

(I)

(II) Polarization

0 40 80 120 160 240 200

Time (min)

Pot

entia

l (V

)

A sequence of Stress/relaxation/EIS repeated several times

(II) Stress: cathodic polarization

(IV) EIS measure (a. c.)

(I) EIS measure (a. c.)

(III) Potential relaxation study

ACCELERATED ELECTROCHEMICAL TECHNIQUES (ACET)

Substrat

NaCl 3.5% Na+

Na+

Na+

Na+

H2O

H2O

H2O

H2O

H2O

H+

H+

H+ H+

H+

H+ H+

Cl-

Cl-

Cl-

Primer

ACET WORKING PROCEDURE

H+

Na+ H2O

H2

OH-

H2

OH-

H2O H2O

Na+

Na+

H2O H2O

H+

H+ H+

Cl-

Cl-

Cl-

2H2O + 2e- → H2 (g) + 2OH-

H. Leidheiser, “Cathodic delamination of polybutadien from steel” J. Adhesion Sci. Tech. 1 (1987) 79.

H+ Na+

Substrat

Primer

NaCl 3.5%

ACET WORKING PROCEDURE

x10 zoom

ACET WORKING PROCEDURE

ACET WORKING PROCEDURE

Field Coil Coating

Substrate 0,27mm Al

Pretreatment Zr/Ti/F

Damage hole

Relaxation potential testing

To obtain additional

information

Corrosion Process

ACET INPROUVEMENT (RELAXATION POTENTIAL TESTING)

EIS (AC)

EIS (AC)

CAT. POL. (DC)

RELAXATION

Coating quality Adhesion

Interface activity

Pore H2O, Ions, Na+

ACET ADDITIONAL INFORMATION

Pore H2O, Ions, Na+

Pore H2O, Ions, Na+

H2

H2

Pore H2O, Ions, Na+

ACET ADDITIONAL INFORMATION

CPEc

Steel Carbon Rs

CPEdl

Rp

CPEc

Rpo

EQUIVALENT CIRCUIT MODELIZATION (ACET)

= Delamination ∆Cdl

= Water absorption ∆Cc

= Corrosion in the interface ∆Rp

= Degradation by porosity increasing ∆Rpo

H2O + e- → 1/2H2↑ + OH-

∆E ∆Z*

Cdl Cc Rp Rpo ) P=f(

ACET ELECTROCHEMICAL DATA SOFTWATE

ELECTROCHEMICAL DATA AND CORRELATION SOFTWARE

INTRODUCTION

THE TECHNIQUE

HISTORY CASES

CONCLUSIONS

Bode Plots (quality of the coating)

The worst behavior The Best behavior

106

1010

ACET BEHAVIOUR OF COATINGS

Plot of the Relaxation potential (adhesion, interface activity)

The best behavior

EOC>-1

The worst behavior

EOC<-1

ACET BEHAVIOR OF COATINGS

ACET APPLIED

TO ISO 12944

PAINT SYSTEMS

ACET BEHAVIOR OF COATINGS

Ref. MedCo Descripción Solicitante Espesor

M0046-1 Pretreated steel+imp. RZ powder+ PE F > 125 µm 168±20 microns

M0046-2 Pretreated steel+imp. RZ powder+ PE F > 125 µm 138±22 microns

M0046-3 Pretreated steel+imp. RZ powder+ PE F > 125 µm 181±23 microns

M0047-2 Pretreated steel+imp. RZ powder+ PE E > 125 µm 165±12 microns

M0047-3 Pretreated steel+imp. RZ powder+ PE E > 125 µm 118±17 microns

M0047-4 Pretreated steel+imp. RZ powder+ PE E > 125 µm 138±8 microns

M0048-1 Pretreated steel+imp. RZ powder+ PE E < 125 µm 123±14 microns

M0048-3 Pretreated steel+imp. RZ powder+ PE E < 125 µm 104±7 microns

M0048-4 Pretreated steel+imp. RZ powder+ PE E < 125 µm 118±14 microns

M0049-2 Pretreated steel+imp. RZ powder+ PE F < 125 µm 116±8 microns

M0049-3 Pretreated steel+imp. RZ powder+ PE F < 125 µm 110±11 microns

M0049-4 Pretreated steel+imp. RZ powder+ PE F < 125 µm 111±11 microns

ACET BEHAVIOR OF COATINGS

REF. MEDCO

EVALUATION (1.296h, M≤1mm)

Blistering Rusting cracking Flaking M=(C-W)/2

M0046-1 0(S0) Ri 0 0(S0) 0(S0) 0,5 M0046-2 0(S0) Ri 0 0(S0) 0(S0) 1,0 M0046-3 0(S0) Ri 0 0(S0) 0(S0) 0,5 M0047-2 0(S0) Ri 0 0(S0) 0(S0) 1,0 M0047-3 0(S0) Ri 0 0(S0) 0(S0) 2,0 M0047-4 0(S0) Ri 0 0(S0) 0(S0) 1,5 M0048-1 0(S0) Ri 0 0(S0) 0(S0) 1,0 M0048-3 0(S0) Ri 0 0(S0) 0(S0) 1,0 M0048-4 0(S0) Ri 0 0(S0) 0(S0) 1,0 M0049-2 0(S0) Ri 0 0(S0) 0(S0) 1,0 M0049-3 0(S0) Ri 0 0(S0) 0(S0) 1,0 M0049-4 0(S0) Ri 0 0(S0) 0(S0) 0,5

M0046~M0049>M0048~M0047

ACET APPLIED TO OFFSHORE PAINT SYSTEMS

M0046~M0049>M0048~M0047

ACET APPLIED

TO OFFSHORE

PAINT SYSTEMS

ISO 20340 175 days

ACET 1 day

ACET APPLIED TO OFFSHORE PAINT SYSTEMS

ISO 20340 175 days

NSS

QUV B

-20ºC

ACET 1 day

RELAXATION

EIS

POLARIZATION

ACET APPLIED TO OFFSHORE PAINT SYSTEMS

# Cliente DFT Cliente DFT MedCo

S1 1:A1 300 302-289

S2 3:C1 300 292-279

S3 1:A2 300 303-288

S4 1:A5 300 300-290

S5 3:A3 300 315-298

S6 3:B1c 300 300-286

S7 2:B5a 300 313-298

S8 2:B6b 300 310-296

S9 5:A2 265 251-240

S10 5:A3 300 311-297

TRILAYER SYSTEM RICH ZINC PRIMER

EPOXI BUILDING COAT PU TOP COAT

ACET APPLIED TO OFFSHORE PAINT SYSTEMS

0

2

4

6

8

10

12

14

0 1 2 3 4 5 6 7 8 9 10 11

mm

DES

LAM

INA

TIO

N

SAMPLES

ACET APPLIED TO OFFSHORE PAINT SYSTEMS

CORRELATION MODEL