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Industry Quality Review
September 2008
NACE Central Area Conference
Magnesium Anode
Electrochemical Properties
-1.75V Open Circuit Voltage
High Potential
-1.55V Open Circuit Voltage
Standard Alloy
1000 Amp-hrs/pound
-
Theoretical
500 Amp-hrs/pound
-
Nominal
50% current efficiency
-
Nominal
Quality & Performance Factors
Alloy Chemistry
Potential (voltage)
Current efficiency
Alloy Chemistry
ASTM B843 defines alloy requirements
>98.5% magnesium
Typically, 100% testing of every heat
Chemistry alone does not identify quality
Open Circuit Potential
Hi-potential magnesium
-1.75V to -1.77V
Standard alloy
-1.50V to -1.55V
Open circuit potential is controlled by chemistry and
casting process
Current Efficiency
% of energy within the alloy that is available
as cathodic protection current
Measured in Amp-Hr/pound
Nominal 50% efficiency for both H-1 and high
potential alloys
Determines life of anode
ASTM G97 test (Destructive test, 14 days, $1000 cost
Anode Life
Life (yrs) = 0.116 x Wt (lbs) x Efficiency x 0.85 (Utiliz. Factor)
Anode Current (amperes)
Value Analysis*
Efficiency
Life (Years)
Annual Cost
50%
16.76
$14.92
40%
13.41
$18.64
30%
10.05
$24.87
20%
6.70
$37.31
*17# anode at 50 mA, Assumes total installed cost of $250
Mag Anode Industry History
Alloy and market development by Dow
Foreign sources (China, Russia, Mexico) entered
market in late 90’s
Initial quality problems with foreign anodes
Foreign quality problems resolved by 1999
US suppliers not competitive with foreign sources
China/Mexico dominant suppliers to US market by 2002
60
Quality
Development
of Foreign
Sources
56
52
48
44
40
36
Early 98
32
Late 98
1999
28
1.65
1.80
1.70
1.75
1.85
OPEN CIRCUIT POTENTIAL IN (-) VOLTS (vs CuCuSO4)
60
56
%CURRENT EFFICIENCY
2002/
2003
Quality
Results
52
48
44
40
36
32
28
1.65
1.75
1.80
1.85
1.70
OPEN CIRCUIT POTENTIAL IN (-) VOLTS (vs CuCuSO4)
2003 Industry Sampling
5 high potential anodes obtained on open
market in mid-2003
Tested according to ASTM G97 standard by
third-party laboratory
Results confirmed widespread quality
problems in industry
2003 Industry Sample Results
Sample
OCP vs
CuCuSO4
Current
Efficiency
Life*
(yrs)
Annual
Cost**
A
-1.75v
49.3%
16.53
$15.12
B
-1.72v
41.6%
13.95
$13.98
C
-1.63v
12.1%
4.06
$61.58
D
-1.63V
11.0%
3.69
$67.75
E
-1.61v
4.8%
1.61
$155.28
*17# anode at 50 mA, **Assumes total installed cost of $250
Quality Concern Validation
Anode quality presentation by T. May (MESA) in
Oct 2003 w/publication in MP in Jan 2004
Anode quality presentation by B. Gummow
(CORRENG) in Feb 2004 at Northern Area
Conference
Anode quality presentation by M. Yunovich
(CCTechnologies) in Mar 2004 at Corrosion 2004
2003 Industry Assessment
Quality concerns apparent in late 2002/2003
Producers capable, but not providing quality
Diminished user quality control programs
Impact of low quality magnesium not well
understood
2005 Industry Sample Results
Sample
OCP vs
CuCuSO4
Current
Efficiency
Life*
(yrs)
Annual
Cost**
A
-1.81
57%
19.11
$13.08
B
-1.79
56%
18.77
$13.32
C
-1.79
55%
18.44
$13.56
D
-1.79
55%
18.44
$13.56
E
-1.68
29%
9.72
$25.72
F
-1.59
16%
5.36
$46.64
*17# anode at 50 mA, **Assumes total installed cost of $250
2005 Industry Assessment
Quality of cast anodes is generally improved
Extruded magnesium anodes are quality
alternative
No significant changes in end-user QA
programs
Still some scrap out there
2007 Industry Sample Results
Sample
OCP vs
CuCuSO4
Current
Efficiency
Life*
(yrs)
Annual
Cost**
A
-1.77
61%
20.45
12.22
B
-1.77
55%
18.44
13.56
C
-1.77
54%
18.1
13.81
D
-1.75
46%
15.42
16.21
E
-1.65
29%
9.72
25.72
F
-1.60
26%
8.72
28.67
G
-1.67
24%
8.05
31.06
H
-1.60
10%
3.35
74.63
*17# anode at 50 mA, **Assumes total installed cost of $250
2007 Industry Assessment
Industry sampling validates continuing
quality concerns
No significant changes in end-user QA
programs
Recent supply instability and price volatility
likely to increase quality concerns
End-User Impact
OCP vs
CuCuSO4
Average
of 2007
tests
Industry
Standard
Current
Efficiency
Life*
(yrs)
Annual
Cost**
-1.70V
38%
12.74
$19.62
-1.75V
50%
16.76
$14.92
+$4.70
*17# anode at 50 mA, **Assumes total installed cost of $250
Conclusions
Anode quality continues to be major industry
concern
Economic impact to industry estimated at
>$2MM per year
End-users and resellers largely unaware or
unconcerned of impact of quality
Instability of magnesium market makes
overall quality improvement unlikely
Industry Quality Review
September 2008
John Cole – MESA Products, Inc.