Corrosion Resistance of CuproBraze Heat Exchangers

Corrosion Corrosion Corrosion Corrosion Corrosion Resistance Resistance
Resistance
Resistance
Resistance
of of
of
of Cu CuproBraze
Cu
Cu
Cu proBraze proBraze
proBraze
Heat Heat Heat Heat Exchangers Exchangers
Exchangers
Exchangers
Exchangers
Markku Ainali
General Manager – Technical Development
Outokumpu Copper Strip AB, Sweden

Contents
Contents
Contents
Contents
Introduction
Accelerated tests
Mixed metal cooling systems
Conclusions

Corrosion Corrosion Corrosion Corrosion Testing
Testing
Testing
Testing
Screening tests
1990 1995 2000
Electrochemical characterisation
Accelerated tests
Mixed metal systems
Tests by rad mfg’s
Tests in vehicles

Is Is Is Is there there there there a a a a risk risk risk risk for for for for galvanic galvanic galvanic galvanic attack attack attack attack attack on on on on the the the the the joints? joints?
joints?
joints?
joints?
Pot. (mV, vs. SCE)
100
0
-100
-200
-300
-400
-500
-600
5% NaCl
Soft solder
1 2 3 4 5 6 7 8 9 10
Exposure duration (days)
Fin
Joint
Tube

Is Is Is Is there there there there a a a a risk risk risk risk for for for for galvanic galvanic galvanic galvanic attack attack attack attack attack on on on on the the the the the joints? joints?
joints?
joints?
joints?
Pot. (mV, vs. SCE)
100
0
-100
-200
-300
-400
-500
-600
5% NaCl
Answer: No!
1 2 3 4 5 6 7 8 9 10
Exposure duration (days)
Fin
Joint
Tube

Is Is Is Is there there there selective selective selective corrosion corrosion corrosion in in in the the the joints?
joints?
joints?
Joints: Joints:
Joints:
Joints: CuSn15P5Ni4
CuSn15P5Ni4
CuSn15P5Ni4
CuSn15P5Ni4
No selective
corrosion!
CuSn Cu 3 P
CuSn+Cu 3 P eut .
Räihä, M, The Electrochemical Properties of a Brazed Cu/Brass Radiator. Master’s Thesis. Helsinki Univ. of Technology, 1999.
Aromaa J, Forsén O, Ainali M and Räihä M, The electrochemical testing of a brazed Cu/brass radiator. ”Electrochemical Methods in
Corrosion Research”- Conference, Budapest, Hungary, 28-31st May, 2000.

Tube Tube Tube Tube Tube Material Material Material Material CuZn15Fe1
CuZn15Fe1
CuZn15Fe1
CuZn15Fe1
vs. vs. vs. vs. Conventional Conventional Conventional Conventional CuZn30 CuZn30 CuZn30 CuZn30 CuZn30 or or or or or CuZn35 CuZn35
CuZn35
CuZn35
CuZn35
More noble due to higher Cu-content
Improved resistance against
dezincification
… and against stress corrosion cracking

Tube Tube Tube Tube Material Material Material Material SM2385 SM2385
SM2385 SM SM2385 SM 2385
General General General General Corrosion Corrosion Corrosion Corrosion and and and and Dezincification
Dezincification
Dezincification
Dezincification
Dezincification comparison:
Alloy Relative scale
SM 1065
SM 1067
SM 1070
SM 1085
SM 1090 general corrosion
SM 2385
SM 2464 pure dezincification
SM 2870
SM 2970

Can Can Can Can we we we we simulate simulate simulate simulate reality?
reality?
reality?
reality?

Accelerated Accelerated Accelerate Accelerated Accelerate d Tests Tests Tests Simulate Simulate Simulate Parts
Parts
Parts
Parts
of of of of the the the the Reality
Reality
Reality
Reality
REP
Salt spray
SWAAT
Marine atmosphere
Cl
S
T
H 2 O
Reality

Accelerated Accelerated Accelerated Accelerated Testing
Testing
Testing
Testing
Ref: SAE 2001-01-1718

REP REP REP REP Test Test
Test
Test
Test
Start
REP
2h 80C
(176 F)
ROOM
AIR 64h
End 336 h
(2 cycles)
WATER
46h 80C
COOLING
6h to RT
Designed to accelerate copper fin corrosion!
SULFIDES
2h 80C
REP
2h 80C
DRYING
6h 80C
WATER
22h 80C
WATER
16h 80C
SULFIDES
2h 80C
REP: 3 w-% NaCl, 2 w-% CaCl 2, 0.03 w-% NaNO 3 ,0.03w-%Na2SO 4,
0.05 w-% Na2 SO 3 , 0.025 w-% NaNO 2 (oxidising, pH 3.5)
SULFIDES: 0.005 w-% Na2 S(formsH2 S in the cabinet)

REP REP REP REP REP Test Test Test Results Results Results 336 336 33
33 6 h
h
h
h
Soldered CuproBraze® Aluminium
Fins: Moderate corr.
Joints: Moderate corr.
Fins: Moderate corr. Fins: Moderate local corr.
Joints: Sligth to moderate local corr.

Salt Salt Salt Salt Spray Spray Spray Spray Test
Test
Test
Test
Most common accelerated corrosion test
Standards ISO 3768, ASTM B117, DIN 50021,
JIS Z2371 etc.
Continuous spray of NaCl 50 g/l, pH 6.5-7.2
Temperature: 35 0 C (95 0 F)

Salt Salt Salt Salt Spray Spray Spray Spray Test Test Test Test Test Results Results Results Results Results 744 744 744 744 Hours
Hours
Hours
Hours
Soldered CuproBraze® Aluminium
Fins: Moderate corr.
Joints: Moderate corr.
Tubes: Sligth corr.
Fins: Slight to moderate corr. Fins: Moderate corr.
Tubes: Slight corr.

SWAAT SWAAT SWAAT WAAT Test
Test
Test
Test
Common test for Al-radiators
Acidified Synthetic Sea Water (Fog) Testing according to
ASTM G43-75/80
Sprayed solution: Synthetic sea salt 42 g/l, pH 2.8-3.0
Temperature: 49 o C (120 o F)
Cycle: 30 min spray, 90 min soak at relative humidity > 98 %.

SWAAT SWAAT SWAAT SWAAT Test Test Test Test Test Results Results Results Results 336 336 336 336 Hours
Hours
Hours
Hours
Soldered CuproBraze® Aluminium
Joints: Moderate corr.
Fins: Sligth to moderate corr.
Joints: Moderate local corr.

Marine Marine Marine Marine Atmosphere
Atmosphere
Atmosp Atmosphere
Atmosp here

Corrosion category C4
for Cu and Al (ISO 9223)
Very heavy test with high
humidity and occasional sea
water splash (chlorides) and
presence of sulfuric pollutants.
Bohus-Malmön, Bohus-Malmön, Bohus-Malmön, Bohus-Malmön, Kvarnvik
Kvarnvik
Kvarnvik
Kvarnvik

Environmental Environmental Environmental Environmental Data
Data
Data
Data
1997 Temp RH ToW Cl - dep SO2-conc NO2-conc Rain pH Cond Cl NO3-N SO4-S NH4-N
0
C % h
2
mg/m d µg/m 3
µg/m 3
mm mS/m mg/dm 3 mg/dm 3 mg/dm 3 mg/dm 3
Jan 0.2* 89* 416* 263 3.2 9.3 10 4.1 11.1 15.6 2.0 3.2 2.0
Feb 1.2 87 483 947 1.8 6.1 61 4.4 10.9 24.1 0.7 1.6 0.5
Mar 2.7 76 383 2306 2.9 4.8 24 4.3 20.7 45.4 1.4 3.3 1.2
Apr 4.6 66 265 1687 0.4 3.1 18 4.9 16.5 40.1 0.7 2.5 0.5
May 8.8 72 307 196 1.3 4.1 79 4.5 3.3 2.8 0.6 0.7 0.5
Jun 15.6 68 178 41 1.4 1.7 29 4.5 3.0 2.6 0.5 0.8 0.2
Jul 18.5 65 155 29 1.1 3.0 19 4.9 1.8 1.3 0.5 0.6 0.3
Aug 20.4 72 194 65 2.5 4.7 51 4.5 2.6 2.2 0.6 0.7 0.5
Sep 13.9 70 214 2761 0.8 2.6 53 4.7 9.3 20.3 0.7 1.5 0.5
Oct 6.9 72 292 943 0.3 3.7 45 4.4 7.6 15.2 0.6 1.3 0.4
Nov 2.9 84 541 490 2.6 8.5 34 4.3 5.1 6.3 1.1 0.8 0.5
Dec 0.4 80 652 103 5.3 11.5 71 4.3 3.3 2.7 0.7 0.6 0.4
Ave 8.0 75 Σ 4080 884 2.0 5.3 Σ 494 4.5 6.7 12.2 0.7 1.2 0.5
Ref: Swedish Corrosion Institute:
Korrosionsinstitutets atmosfäriska
fältstationer, Miljö- och korrosionsdata 1997

Exposure Exposure Exposure xposure Start Start Start in in in June June June June 1999
1999
1999
Aluminium CuproBraze ® Soldered

Controls Controls Controls Controls in in in in Aug. Aug. Aug. Aug. 2000 2000 2000 2000 and and and and May May May Ma May Ma May
y 2001 2001
2001
2001

Marine Marine Marine Marine Atmosphere Atmosphere Atmosphere Atmosphere – – – – Soldered Soldered
Soldered
Soldered
Soldered
Joints: Moderate corr.
Tubes: Slight dezincification
15 Months 22.5 Months
Joints: Heavy corr.
Tubes: Deep dezincification

Marine Marine Marine Marine Atmosphere Atmosphere Atmosphere Atmosphere – – –
–
– Cu Cupro Cu
Cu
Cu proBraze proBraze pro proBraze pro Braze
Fins:Slightcorr.
15 Months 22.5 Months
Fins:Slightcorr.
Joints: Slight corr.

Fin
Marine Marine Marine Marine Atmosphere Atmosphere Atmosphere Atmosphere Atmosphere - - - - Aluminium
Aluminium
Aluminium
Aluminium
15 Months 22.5 Months
Fins: Moderate local corr.
Joints: Moderate local corr.
Joint
Mostly slight even corr.

Marine Marine Marine Marine Atmosphere Atmosphere Atmosphere Atmosphere Corrosion Corrosion Corrosion Corrosion Forms
Forms
Forms
Forms
15 monhs
Soldered CuproBraze® Aluminium

Corrosion Corrosion Corrosion Corrosion Corrosion Test Test Test Test Test Winners Winners
Winners
Winners
Winners
Marine atm.
REP SWAAT Salt Spray
Aluminium CuproBraze
Ref: SAE 2001-01-1718

Corrosion Corrosion Corrosion Corrosion Corrosion Test Test Test Test Test Winners Winners
Winners
Winners
Winners
REP SWAAT Salt Spray
Marine atm.
Aluminium CuproBraze
Ref: SAE 2001-01-1718

Powder coating
Further Further Further Further Improvements
Improvements
Impro Improvements
Impro vements
Electrocoating

Mixed Mixed Mixed Mixed Metal Metal Metal Metal Metal Systems
Systems
Systems
Systems
Tapio Korpinen, Outokumpu Copper R&D
Based on Paper Nr 2001-01-1754 “Electrochemical Tests With
Copper/Brass Radiator Tube Materials in Coolants”
presented at SAE-VTMS 2001

Question:
Question:
Question:
Question:
Does copper
cause micro-galvanic
corrosion on aluminum
in cooling systems?

Test Materials and Environments
Brass CuZn15Fe1, CuZn30, and aluminum AA3003
Commercial antifreezes:
Ethylene glycol with conventional inhibitors
Ethylene glycol with modern OAT inhibitors
Test solutions: 20 vol-% of antifreeze diluted with
ASTM D1384 corrosive water .

ASTM Corrosive orrosive Water ater
Component mg/l in distilled water
Na 2 SO 4 148
NaCl 165
NaHCO 3 138
PH values of the glycol solutions were:
7.4 for solution A
8.3 for solution B

Test Cell
Counter-electrode: Pt
Ref. electrode: Ag/AgCl
Temp.: 85 0 C
Stirring 350 r/min
Liquid volume 1.0 l

Test Test Test Test Test Methods
Methods
Methods
Methods
Potential vs. time
Potentiodynamic polarization and
corrosion rate
Galvanic corrosion test

Results : Potential and corrosion rate
Potential
in Glycol A
Potential
in Glycol B
Corrosion rate
in Glycol A
Corrosion rate
in Glycol B
SM2385 SM1070 AA3003
-16 mV -24 mV -867 mV
-38 mV -62 mV -512 mV
2 um/a 5 um/a not defined
8 um/a 21 um/a not defined

Galvanic Test
The galvanic corrosion test was very severe
The potential of aluminum was shifted to the potential of
copper with impressed current
Potential and current were monitored for 30 days

Conclusions Conclusions Conclusions Conclusions - - -
-
- Cu CuproBraze
Cu
Cu
Cu proBraze proBraze
proBraze
Improved corrosion resistance compared to
soldered radiators
Very competitive with aluminium radiators
Predictable behaviour
Compatible with mixed metal systems

Thank Thank Thank Thank Thank you you you you for for for for your your your your your attention!
attention!
attention!
attention!