CORROSION MITIGATION IN BALCONY REPAIRS What is ...
CORROSION MITIGATION IN BALCONY REPAIRS What is ...
CORROSION MITIGATION IN BALCONY REPAIRS What is ...
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<strong>CORROSION</strong> <strong>MITIGATION</strong> <strong>IN</strong><br />
<strong>BALCONY</strong> <strong>REPAIRS</strong><br />
KATHER<strong>IN</strong>E A. KLOSOWSKI-BLATZ<br />
<strong>What</strong> <strong>is</strong> Corrosion?<br />
In steel reinforced concrete, corrosion <strong>is</strong> the deterioration of steel caused by a<br />
change in its concrete surroundings (environment).<br />
The “chemical change” can be brought on by many different factors:<br />
• CHLORIDES<br />
• CARBONATION<br />
• SULFATE ATTACK<br />
• DISSIMILAR METALS<br />
04.11.2004 2
CAST <strong>IN</strong> CHLORIDES<br />
CARBONATION<br />
WATER + CARBON DIOXIDE
DISSIMILAR METALS<br />
BASIC TERM<strong>IN</strong>OLGY<br />
• PASSIVAT<strong>IN</strong>G LAYER: Iron Oxide film on steel that naturally<br />
inhibits corrosion (mill scale).<br />
• Basically a thin layer of RUST that naturally protects the steel. It<br />
<strong>is</strong> stable so long as the concrete at the steel-concrete interface<br />
has an alkalinity of ph 10 or greater
WHY DO WE GET SPALL<strong>IN</strong>G?<br />
RUST EXPANDS TO 8 TIMES<br />
THE VOLUME OF STEEL<br />
LEAD<strong>IN</strong>G TO LOSS OF<br />
STRUCTURAL <strong>IN</strong>TEGRITY<br />
04.11.2004 7<br />
<strong>CORROSION</strong><br />
ALUM<strong>IN</strong>UM RAILS
BASIC TERM<strong>IN</strong>OLOGY<br />
• ANODE: Electrode at which net Oxidation Process occurs, th<strong>is</strong> <strong>is</strong><br />
where you see rust<br />
• CATHODE: Electrode at which a net Reduction Reaction occurs<br />
• ELECTROLYTE: Solution containing ions (Cl-, OH-) (CONCRETE)<br />
• RESISTIVITY – A measure of the ability of an electrolyte to res<strong>is</strong>t<br />
the flow of electric charge<br />
Patch Accelerated Corrosion<br />
“Incipient Anode”<br />
04.11.2004 10
BASIC TERM<strong>IN</strong>OLOGY<br />
RELATIVE HUMIDITY<br />
Corrosion Currents, uA<br />
600<br />
UNTREATED<br />
500<br />
400<br />
300<br />
200<br />
100<br />
0<br />
45 50 55 60 65 70 75 80 85 90 95 100 95 90 85 80 75<br />
Wetting Cycle<br />
% Relative Humidity<br />
Drying Cycle<br />
04.11.2004 11<br />
BASIC TERM<strong>IN</strong>OLOGY<br />
• DISSILIMAR METALS – two metal<br />
components in an electrolyte that<br />
could form an anode-cathode<br />
relationship when connected by a<br />
metallic path<br />
Gold<br />
316 SS<br />
Steel<br />
• ELECTROMOTIVE SERIES - l<strong>is</strong>t<br />
of metals whose order indicates<br />
the relative tendency to be<br />
oxidized, or to give up electrons<br />
Chromium<br />
Zinc<br />
Aluminum
<strong>CORROSION</strong>:<br />
<strong>What</strong> Do You Need?<br />
• Steel (Fe++)<br />
• Chlorides (Cl-)<br />
• Oxygen (O 2 )<br />
• Water (H 2 O)<br />
or another metal<br />
• OTHER Symbols to know<br />
• Electrons (e-) like a battery corrosion has an electrical current<br />
• Hydroxyl (OH-) basic / alkali available in concrete solution<br />
• Hydrogen (H+) acid – causes the pH to lower<br />
Electrochemical Corrosion Reactions<br />
•Fe ++ + 2Cl - FeCl 2<br />
•FeCl 2 + H 2 O + OH - Fe(OH) 2 + H + + 2Cl -<br />
•2Fe(OH) 2 + ½O 2<br />
-<br />
Fe 2 O 3 + 2H 2 O anode<br />
•½O 2 + H 2 O + 2e - 2 OH - cathode<br />
04.11.2004 14
<strong>CORROSION</strong> PROCESS<br />
l<br />
Corrosion <strong>is</strong> like a chain.<br />
The entire process can be<br />
interfered with if a link <strong>is</strong> broken.<br />
Initiator<br />
Water + Oxygen<br />
Concrete Reinforcing<br />
Fe +2<br />
+2<br />
A<br />
Passive layer<br />
no<br />
d<br />
e<br />
04.11.2004 15<br />
2 e -<br />
Cath<br />
ode<br />
2 OH OH<br />
<strong>CORROSION</strong> PREVENTION OPTIONS<br />
New Construction<br />
• COATED REBAR<br />
• NON-STEEL REBAR<br />
• ADMIXTURES<br />
• WATER REPELLENTS<br />
• DECK COAT<strong>IN</strong>GS / MEMBRANES<br />
04.11.2004 16
<strong>CORROSION</strong> CONTROL OPTIONS<br />
Restoration<br />
• REMOVAL OF CONTAM<strong>IN</strong>ATED CONCRETE<br />
• REBAR COAT<strong>IN</strong>GS<br />
• Epoxy<br />
• Cementicous<br />
• PATCH REPAIR MATERIAL WITH CI / W/O CI<br />
• FRP<br />
• GALVANIC PROTECTION<br />
• Zinc Rich Rebar Primers<br />
• Galvanic Anodes<br />
• ELECTROCHEMICAL OPTIONS<br />
• ICCP – Impressed Current Cathodic Protection<br />
• Chloride Extraction / Re-Alkalinization<br />
• ANTI-CARBONATION TREATMENTS<br />
• SURFACE APPLIED <strong>CORROSION</strong> <strong>IN</strong>HIBITORS<br />
REMOVE CONTAM<strong>IN</strong>ATED<br />
CONCRETE
REMOVAL OF CONTAM<strong>IN</strong>ATED<br />
CONCRETE<br />
REBAR COAT<strong>IN</strong>G AND BOND<strong>IN</strong>G AGENT
04.11.2004 21<br />
GALVANIC PROTECTION<br />
Zinc Rich Primers
GALVANIC PROTECTION<br />
Galvanic Anodes<br />
GALVANIC PROTECTION<br />
Anodes
PERIMETER <strong>REPAIRS</strong><br />
REPAIR MORTARS<br />
with or without C.I.
REPAIR MATERIALS<br />
• SCHOOLS OF THOUGHT<br />
1. Match the host concrete character<strong>is</strong>tics<br />
2. Polymer modified, high strength, high density mortars<br />
ELECTRICAL POTENTIAL<br />
DIFFERENTIAL<br />
04.11.2004 28
GALVANIC PROTECTION<br />
Anodes Need Conductive Environment<br />
Repair Mortar<br />
must have a<br />
res<strong>is</strong>tivity of less<br />
than<br />
15,000 Ohms-cm<br />
RAIL<strong>IN</strong>G GROUT POCKETS
Effectiveness of Various Protection<br />
Materials on Active Corrosion<br />
Urethane<br />
Membrane<br />
Silane/Acrylic<br />
Cementitious Coating<br />
Tested at 60%<br />
Relative Humidity<br />
Silane Sealer<br />
<strong>CORROSION</strong> <strong>IN</strong>HIBITOR<br />
Tested at 85%<br />
Relative Humidity<br />
0 20 40 60 80 100<br />
% Reduction in Corrosion<br />
Conventional protection methods may prevent corrosion,<br />
but they are not as effective on active corrosion<br />
04.11.2004 31<br />
Silanes:<br />
Made with Different Functionality<br />
(C 2<br />
H 5<br />
O) 3<br />
Si<br />
Alkyltrialkoxysilane<br />
Hydrophobic Effect<br />
H 2 N<br />
Si(OC 2 H 5 ) 3<br />
Aminoalkyltrialkoxysilane<br />
Corrosion inhibitor<br />
F C 3<br />
CF 2<br />
CF2<br />
CF 2<br />
CF2<br />
CF 2<br />
CH2<br />
CH 2<br />
Si(OC2 H 5 ) 3<br />
FluoroAlkyltrialkoxysilane<br />
R f<br />
Anti-Graffiti, Easy to Clean<br />
R f<br />
O<br />
Si<br />
O<br />
X<br />
H<br />
O<br />
O<br />
Si<br />
Si<br />
O<br />
O<br />
Si<br />
O<br />
O<br />
Si<br />
Si<br />
O<br />
Silane Molecule<br />
Substrate e.g. Concrete<br />
04.11.2004 32
Corrosion Inhibitors<br />
• Inorganic Inhibitors<br />
• Organic Inhibitors<br />
• Cathodic<br />
• Anodic<br />
• Mixed<br />
Corrosion inhibitors are used to prevent or delay corrosion<br />
of metals exposed to corrosive environments.<br />
Cathodic inhibitors decrease cathodic corrosion reaction.<br />
Anodic inhibitors decrease anodic corrosion reaction.<br />
Mixed inhibitors decrease cathodic and anodic corrosion reaction.<br />
04.11.2004 33<br />
Corrosion Continuing<br />
04.11.2004 34
<strong>CORROSION</strong> <strong>IN</strong>HIBITOR<br />
Properties of an Effective<br />
Corrosion Inhibitor<br />
• Works on both chloride and carbonation induced corrosion – in concrete.<br />
• Effective in high humidity environments<br />
• Must change electrical properties of steel/concrete<br />
• Long service life<br />
• Effective on concrete with micro-cracks<br />
• Proven Laboratory and Field Results<br />
04.11.2004 36
SURFACE APPLIED <strong>CORROSION</strong> <strong>IN</strong>HIBITOR<br />
Ex<strong>is</strong>ting Corrosion in Concrete<br />
600<br />
500<br />
Current, µA<br />
400<br />
300<br />
200<br />
100<br />
Untreated<br />
<strong>CORROSION</strong><br />
<strong>IN</strong>HIBITOR<br />
0<br />
0 1 5 10 15 20 25 30 35 40 45 48<br />
Weeks of Salt Water Exposure<br />
Corrosion on Cracked Specimens<br />
Corrosion on Cracked Specimens for Different Systems Using FHWA-<br />
RD-98-153 Protocol<br />
• Black Bars -- 4053 mV<br />
• Epoxy, 0.5% damage -- 971 mV<br />
• Epoxy, 0.004% damage -- 325 mV<br />
• Copper-clad -- 111 mV<br />
• 316 SS -- 5 mV<br />
• SURFACE APPLIED <strong>CORROSION</strong> <strong>IN</strong>HIBITOR -- 58 mV
FIELD PERFORMANCE<br />
TEST IT!!!<br />
39<br />
Performance of<br />
Corrosion Inhibitor<br />
Corrosion Rate Before C.I. CP<br />
Corrosion Rate After CP C.I.<br />
04.11.2004 40
BUT WAIT…..<br />
• WHAT ABOUT CRACKS???<br />
• ONCE <strong>CORROSION</strong> IS MITIGATED…..then you MAY be able to<br />
install a coating or crack sealer.<br />
DECK COAT<strong>IN</strong>GS<br />
• Improve appearances of patchy surfaces<br />
• Provide water-proofing<br />
• Prevent new chlorides<br />
• EXCELLENT <strong>IN</strong> “LOW COVER” Problem areas
DECK COAT<strong>IN</strong>GS<br />
• WATCH OUT FOR<br />
• Breathability<br />
• Durability<br />
• SURFACE PREP REQUIREMENTS<br />
REVIEW<br />
• LOTS OF OPTIONS!<br />
• Know the root cause of your corrosion<br />
• STOP IT FIRST!<br />
• Match the repair solution to the problem<br />
• Don’t assume …..check compatibilities<br />
• Remember to use galvanic anodes repair material must have a<br />
res<strong>is</strong>tivity of less than 15,000 ohms-cm<br />
• Isolate d<strong>is</strong>similar metals so electrical potential differentials<br />
cannot be establ<strong>is</strong>hed
THANK YOU!<br />
THANK YOU.<br />
BASF Construction Chemicals, LLC –<br />
Building Systems<br />
889 Valley Park Drive<br />
Shakopee, MN 55379<br />
952-496-6000 Phone
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