for reinforcement steel Hilke Verbruggen (hverbrug@vub.ac.be) a,b , - - PowerPoint PPT Presentation

▶
for reinforcement steel
SMART_READER_LITE
LIVE PREVIEW

for reinforcement steel Hilke Verbruggen (hverbrug@vub.ac.be) a,b , - - PowerPoint PPT Presentation

May 21, 2023 43 likes •386 views

Study and evaluation of active corrosion protection coatings for reinforcement steel Hilke Verbruggen (hverbrug@vub.ac.be) a,b , Florian Hiemer c , Sylvia Keler c , Christophe Gehlen c , Herman Terryn a , Iris De Graeve a a Research Group

slide-1
SLIDE 1

Study and evaluation of active corrosion protection coatings for reinforcement steel

Hilke Verbruggen (hverbrug@vub.ac.be)a,b, Florian Hiemer c, Sylvia Keßler c, Christophe Gehlen c, Herman Terryn a, Iris De Graeve a

a Research Group Electrochemical and Surface Engineering (SURF)

Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium

b SIM vzw, Technologiepark 935, B-9052 Zwijnaarde, Belgium c Centre for Building Materials, Technische Universität München,

Baumbachstrasse 7, 81245 Munich, Germany

slide-2
SLIDE 2

deredactie.be Adapted from DS-infografiek (deredactie.be)

2

slide-3
SLIDE 3

Problem?  Spalling!

http://www.consysinc.net/ combating-corrosion.php https://civildigital.com/spalling-concrete- causes-prevention-repair/

3

slide-4
SLIDE 4

Chlorides attack the passivation layer Pitting corrosion

How?

CO2 reacts with Ca(OH)2 to form CaCO3 (=carbonation) Drop of pH (pH < 10) Uniform corrosion In a concrete environment (pH ≈ 13)  steel is passivated. However, with the ingress of corrosive species corrosion can occur

4

slide-5
SLIDE 5

Strategies to avoid the problem?

Application of a coating Corrosion inhibitors Application of additional concrete cover

Physical barrier Active protection

Cathodic protection

5

slide-6
SLIDE 6

= Double corrosion protection

Physical barrier Active protection

+

= Active corrosion protection coatings for reinforced concrete

6

slide-7
SLIDE 7

Outline

  • Previous work

Evaluation of inhibitors in different concrete pore solutions

  • Application/incorporation of the inhibitor

On the rebar/into an epoxy coating

  • Evaluation of the coatings in concrete

First results

7

slide-8
SLIDE 8

Previous work

Evaluation of inhibitors in different concrete pore solutions

8

  • H. Verbruggen, H. Terryn, I. De Graeve, Inhibitor evaluation in different simulated

concrete pore solution for the protection of steel rebars, Construction and Building Materials 124 (2016) 887—896.

slide-9
SLIDE 9

9

0.3 V 0.6 V

Screening of inhibitors against pitting corrosion

All tested inhibitors, except for BTA, show some inhibition by counteracting the effect of salt and shifting the breakdown potential to 0,6 V.

slide-10
SLIDE 10

Screening of inhibitors against uniform corrosion

10

In this case only sodium molybdate shows some corrosion inhibition

slide-11
SLIDE 11

Microscopic evaluation confirms Na2MoO4 can inhibit both pitting and uniform corrosion

11

Pitting corrosion Uniform corrosion

Without inhibitor With Na2MoO4

  • H. Verbruggen, H. Terryn, I. De Graeve, Inhibitor evaluation in different simulated

concrete pore solution for the protection of steel rebars, Construction and Building Materials 124 (2016) 887—896.

slide-12
SLIDE 12

Application/incorporation

  • f the inhibitor

On the rebar/into an epoxy coating

12

slide-13
SLIDE 13

Mixing in molybdate

BECOPOX coating (Allnex): a water-based epoxy coating We prepared 36 % solid content to have the right viscosity for spray coating (0,06 – 0,1 Pa.s) We mixed 1 wt% (on solid content) Na2MoO4 with the hardener and water (before adding the epoxies)

13

slide-14
SLIDE 14

Molybdate pretreatment

Inspired by

  • “Active corrosion protection of steel by Ce

containing conversion films”, R. Ramanauskas,

EUROCORR 2016, Montpellier, France, 15 September 2016.

  • “Molybdate conversion coatings on zinc surfaces”,

A.A.O. Magalhães et al.,

Journal of Electroanalytical Chemistry 572 (2004) 433-440.

We prepared a bath of 0.3 M Na2MoO4 acidified with H3PO4 (pH 3) and left the steel in for 10 min.

14

slide-15
SLIDE 15

Evaluation of the coatings in concrete

First results

15

In collaboration with Centre for Building Materials, Technische Universität München

slide-16
SLIDE 16

Preparation of samples

Bare steel (bs) Reference coating (refcoat) Inhibitor mixed in the coating (ic) Inhibitor pretreatment (ip) Inhibitor pretreatment with coating on top (ipc) Rebars were spraycoated at OCAS; two layers were applied  thickness ≈ 40 µm (!)

slide-17
SLIDE 17

Preparation of the samples

17

Side view: Top view: anode cathode TiO2 mesh (counterelectrode) MnO2 reference electrode

slide-18
SLIDE 18

Preparation of samples

18

Top view: In the coated samples (i.e. refcoat, ic, and ipc) a defect was applied by screwing a drill by hand, in both the anode and cathode  Defect size = 0.2 mm²

slide-19
SLIDE 19

Preparation of samples

anode cathode TiO2 mesh (CE) MnO2 reference electrode

slide-20
SLIDE 20

Preparation of the samples

slide-21
SLIDE 21

Preparation of samples

A crack (0.3 mm at surface) was introduced above the anode to simulate the worst condition

slide-22
SLIDE 22

Set-up

In cracked region weekly addition of 100 ml 1.5 % NaCl solution In outer regions weekly addition of tap water

slide-23
SLIDE 23

Measurements in concrete

23

Top view:

The corrosion current is recorded every 3 hours

anode cathode

slide-24
SLIDE 24

Measurements in concrete

24

Side view:

Every week the corrosion potential is measured

anode cathode RE WE CE MnO2 RE

slide-25
SLIDE 25

Measurements in concrete

25

Side view:

Every week the IR drop is measured

anode cathode RE WE CE

+

MnO2 RE

slide-26
SLIDE 26

Measurements in concrete

26

Side view:

Every week – after depolarisation – the OCP of the anode is measured

anode RE WE CE TiO2 mesh MnO2 RE

LPR anode

(Gamry) the polarization resistance of the anode is measured

slide-27
SLIDE 27

LPR cathode

(Gamry) Every week – after depolarisation – the OCP of the cathode is measured the polarization resistance of the cathode is measured

Measurements in concrete

27

Side view: cathode RE WE CE TiO2 mesh MnO2 RE

slide-28
SLIDE 28

First results (after 12 weeks)

28

  • 800
  • 600
  • 400
  • 200

0.000 0.005 0.010 14 28 42 56 70 84 98 Potential (mVMnO2) Time since first addition of NaCl solution (d) Macro corrosion current OCP anode OCP cathode Corrosion potential

Macro corrosion current (mA) Potential (mVMnO2)

Bare steel (bs 1)

0.002

  • 310
slide-29
SLIDE 29

29

First results (after 12 weeks)

  • 800
  • 600
  • 400
  • 200

0.000 0.005 0.010 14 28 42 56 70 84 98 Time since first addition of NaCl solution (d) Macro corrosion current OCP anode OCP cathode Corrosion potential

Macro corrosion current (mA) Potential (mVMnO2) 0.006

  • 579

Reference coating (E+J)

slide-30
SLIDE 30

30

First results (after 12 weeks)

  • 800
  • 600
  • 400
  • 200

0.000 0.005 0.010 14 28 42 56 70 84 98 Time since first additon of NaCl solution (d) Macro corrosion current OCP anode OCP cathode Corrosion potential

Inhibitor mixed in the coating (ic OP)

Macro corrosion current (mA) Potential (mVMnO2)

  • 531

0.002

slide-31
SLIDE 31

First results (after 12 weeks)

31

  • 800
  • 600
  • 400
  • 200

0.000 0.005 0.010 14 28 42 56 70 84 98 Time since first addition of NaCl solution (d) Macro corrosion current OCP anode OCP cathode Corrosion potential

Macro corrosion current (mA) Potential (mVMnO2)

Inhibitor pretreatment (ip 5+11)

  • 398

0.000

slide-32
SLIDE 32
  • 800
  • 600
  • 400
  • 200

0.000 0.005 0.010 14 28 42 56 70 84 98 Time since first addition of NaCl solution (d) Macro corrosion current OCP anode OCP cathode Corrosion potential

  • 262

First results (after 12 weeks)

32

Macro corrosion current (mA) Potential (mVMnO2)

Inhibitor pretreatment + coating (ipc 5+10)

0.000

slide-33
SLIDE 33

Short overview (after 12 weeks)

Sample Corrosion potential, Ecorr (mV) IR Drop (mV) Driving potential, ΔE (mV) Rp (kΩ) Bare steel

  • 310

51 20.17 Reference coating

  • 579

12 218 4.37 Inhibitor mixed in

  • 531

20 191 13.73 Inhibitor pretreatment

  • 398
  • 22

18.18 Inhibitor pretreatment + coating

  • 262

8 18.25

33

slide-34
SLIDE 34

(Mid-term) conclusions & outlook

Bare steel needs some time to form a passive layer

34

The (damaged) epoxy coating seems to favour corrosion When the inhibitor is mixed into the coating it can prolongate the initiation phase The inhibitor pretreatment (+ coating) rebars are protected from the beginning  promising!

Does it also protect on the long term?! What happens inside the concrete?