Final report

Material 
Color Measurement – CIE 
L 
a 
b 
Cupronickel (Incumbent Material) 
76.3 
0.8 
6.7 
Dura-White-Plated Zinc 
89.7 
–0.7 
5.8 
Multi-Ply-Plated Steel (Lot # 11-137) 
77.8 
0.6 
8.9 
Multi-Ply-Plated Steel (Lot # 11-170) 
81.6 
1.2 
8.1 
Nickel-Plated Steel 
84.3 
0.3 
7.3 
G6 Mod 
88.4 
–1.2 
14.1 
302HQ Stainless Steel (blanked at CTC) 
72.1 
0.9 
4.9 
430 Stainless Steel 
73.1 
0.2 
1.7 
669z 
86.0 
0.4 
15.3 
Nickel-Plated 31157 
78.5 
0.7 
10.5 
Unplated 31157 
84.3 
–1.0 
30.1 
Table 2-17. 
Color Measurement of Quarter Dollar Coin Alternative Material Candidates 
Material 
Color Measurement – CIE 
L 
a 
b 
Cupronickel-Clad C110 (Incumbent Material) 
78.5 
1.0 
7.0 
Multi-Ply-Plated Steel 
77.6 
0.9 
9.4 
Nickel-Plated Steel 
81.1 
0.50 
8.5 
669z-Clad C110 
83.6 
2.3 
16.7 
302HQ Stainless Steel 
75.5 
0.4 
6.7 
Dura-White-Plated Zinc 
89.6 
–0.5 
5.9 
53  

Table 2-18. 
Color Measurement of Dollar Coin Alternative Material Candidates 
Material 
Color Measurement – CIE 
L 
a 
b 
Manganese Brass-Clad C110 (Incumbent Material) 
82.3 
2.9 
14.6 
88Cu-12Sn-Plated Zinc 
79.3 
7.9 
20.3 
C69250 
80.8 
1.7 
13.6 
K474 
81.9 
0.5 
15.5 
2.4.1.6  Grain Size 
Phase 2 grain size measurements and typical photomicrographs of each test material are shown in 
Tables 2-19 through 2-21.  Alternative material candidates used in more than one denomination 
are only shown once among these three tables.  The reported grain size represents a statistical 
mean of grains using the ASTM E112 methodology [5].  In cases where the grains are not 
approximately the same overall dimension in all directions, the ASTM E112 methodology 
declares the grains ‘deformed’ and the method cannot be used.  Those instances are denoted in the 
tables with an asterisk; engineering estimates are provided for typical grain dimensions for these 
cases.  Grain sizes over 50 microns (μm) have been correlated with visible surface finish 
problems for incumbent coinage materials.  This is often referred to as “orange peel” due to the 
mottled appearance of surfaces showing this effect.  Material with a grain size greater than 50 μm 
is therefore undesirable. 
54  

Table 2-19. 
Grain Size of One-Cent Coin Alternative Material Candidates 
Material 
Mean Grain 
Size (microns) 
Photomicrograph 
Aluminized Steel (Ryerson) 
7.7 
Aluminized Steel (Atlas) 
12.1 
Al-Mg Alloy 5052-H32 
20 by 80* 
Copper-Plated Steel (JZP) 
17.9 
430 Stainless Steel 
9.8 
55  

Table 2-20. 
Grain Size of 5-Cent Coin Alternative Material Candidates 
Material 
Mean Grain 
Size (microns) 
Photomicrograph 
Cupronickel (Incumbent Material) 
23.0 
Dura-White-Plated Zinc 
varied 
Multi-Ply-Plated Steel (Lot # 11-137) 
21.5 
Multi-Ply-Plated Steel (Lot # 11-170) 
19.8 
G6 Mod 
49.5 
56  

Table 2-20. 
Grain Size of 5-Cent Coin Alternative Material Candidates (continued) 
Material 
Mean Grain 
Size (microns) 
Photomicrograph 
302HQ Stainless Steel 
76.2 
430 Stainless Steel 
8.8 
669z 
20.7 
Plated 31157 
23.0 
57  

Table 2-21. 
Grain Size of Quarter Dollar Coin Alternative Material Candidates 
Mean Grain 
Material 
Size (microns) 
Photomicrograph 
Cupronickel-Clad C110 (Incumbent 
22.4 
Material) 
Multi-Ply-Plated Steel 
19.2 
669z-Clad on C110 
19.1 
2.4.2  Round One Str iking Tr ails 
Progressive striking trials were conducted for each alternative material candidate.  Round One 
striking tests consisted of approximately 4.5-kg (10-lb) lots of each candidate material, with the 
single exception of the 430 stainless steel in one-cent gage.  This material was undersized and too 
thin to feed reliably through the striking press.  Tables 2-22 through 2-24 show the striking loads 
used to produce the Round One (40-piece) lots of nonsense pieces.  In most cases the materials 
performed in similar fashion to the incumbent materials.  The exceptions were the aluminized and 
stainless steels.  At nominal striking loads or even at the highest safe striking load permitted by 
the coin presses and dies, nonsense pieces produced with aluminized and stainless steel did not 
exhibit complete coin fill (i.e., the struck imagine lacked some details of the desired image). 
Incumbent materials were struck in advance of Round One striking trials in order to generate 
baseline data; information related to incumbent coinage materials is included in the tables for 
comparison only. 
58  

Table 2-22. 
Progressive Strike Results for One-Cent Coin Alternative Material Candidates –  
Round One  
Material 
Test Coin 
Striking Load 
(tonne) 
Difference from 
Incumbent Coin 
(tonne) 
Comment 
Copper-Plated Zinc (Incumbent Material) 
40 
-­
N/A 
Aluminized Steel (Ryerson) 
50 
+10 
Insufficient coin fill 
Aluminized Steel (Atlas) 
50 
+10 
Insufficient coin fill 
Al-Mg Alloy 5052-H32 
35 
–5 
None 
Copper-Plated Steel 
40 
0 
None 
430 Stainless Steel 
N/A 
N/A 
Too thin to strike 
Table 2-23. 
Progressive Strike Results for 5-Cent Coin Alternative Material Candidates –  
Round One  
Material 
Test Coin 
Striking Load 
(tonne) 
Difference from 
Incumbent Coin 
(tonne) 
Comment 
Cupronickel (Incumbent Material) 
54 
-­
N/A 
Dura-White-Plated Zinc 
54 
0 
None 
Multi-Ply-Plated Steel (Lot # 11-137) 
54 
0 
Met low end of 
dimensional 
specifications* 
Multi-Ply-Plated Steel (Lot # 11-170) 
54 
0 
Met low end of 
dimensional 
specifications* 
G6 Mod 
54 
0 
None 
669z 
54 
0 
None 
Nickel-Plated 31157 
54 
0 
None 
302HQ Stainless Steel (blanked at CTC) 
70 
+16 
Insufficient coin 
fill 
302HQ Stainless Steel (blanked by 
Carpenter Technology) 
70 
+16 
Insufficient coin 
fill 
430 Stainless Steel 
70 
+16 
Insufficient coin 
fill 
* United States Mint’s finished coin specifications for incumbent coins. 
59  

Table 2-24. 
Progressive Strike Results for Quarter Dollar Coin Alternative Material Candidates 
– Round One 
Material 
Test Coin 
Striking Load 
(tonne) 
Difference from 
Incumbent Coin 
(tonne) 
Comment 
Cupronickel-Clad C110 (Incumbent 
Material) 
62 
-­
N/A 
Multi-Ply-Plated Steel 
62 
0 
None 
669z-Clad C110 
62 
0 
None 
2.4.3  Obser vations fr om Str iking Tr ails – Round One 
Nonsense pieces were successfully produced from most of the candidate materials.  Photographs 
of nonsense pieces produced at the specified press tonnage are included below.  Surface details 
can be reliably compared in these photographs.  Note however that the lighting conditions were 
not optimized for photography; therefore colors in the photographs that follow are not reliable 
indications of the actual nonsense piece colors. 
2.4.3.1  One-Cent Nonsense Pieces 
One-cent nonsense pieces of aluminized steel from Atlas and Ryerson are shown in Figure 2-1. 
These nonsense pieces were struck at 50 tonnes.  Note that 40 tonnes is the nominal striking load 
for the incumbent copper-plated zinc one-cent coin. 
Figure 2-1. 
Aluminized steel one-cent nonsense pieces struck at 50 tonnes. 
(a)  Atlas Material 
(b)  Ryerson Material 
Aluminum alloy 5052-H32 purchased from a warehouse showed excellent coin fill at low striking 
loads (Figure 2-2).  Note that a mechanical malfunction caused the dies to clash before the 5052­
H32 nonsense pieces were struck.  The damage resulting from the die clash caused some blurring 
60  

of the letters.  Nevertheless the 5052-H32 had excellent surface detail at a low striking load of 35 
tonnes. 
Note:  The visible scoring is from a die clash that damaged the dies before this nonsense piece 
was struck. 
The copper-plated steel planchets produced by JZP (Figure 2-3) displayed good fill at a nominal 
striking load of 40 tonnes. 
Grade 430 stainless steel was purchased from a warehouse and was significantly under the gage 
ordered; therefore, it did not feed properly into the press.  The progressive striking trial was halted 
after a die clash when it was determined that the sample pieces were getting stuck underneath the 
Figure 2-3. 
JZP copper-plated steel one-cent nonsense piece struck at 40 tonnes. 
Figure 2-2. 
5052-H32 one-cent nonsense piece struck at 35 tonnes. 
61  

feed fingers.  Those 430 stainless steel nonsense pieces that were successfully struck were found 
to have inadequate coin fill. 
2.4.3.2  5-Cent Nonsense Pieces 
The Dura-White material provided by JZP comprised copper plated on a zinc alloy (A190) and 
subsequentially plated with tin.  The Dura-White-plated zinc was struck at 54 tonnes.  This 
material showed good coin fill as noted in Figure 2-4. 
Figure 2-4. 
Dura-White-plated zinc 5-cent nonsense piece struck at 54 tonnes. 
The Multi-Ply-plated steel material striking trials were performed at 54 tonnes, the nominal 
striking load for the incumbent 5-cent coin.  The surface was shiny and attractive as seen in 
Figure 2-5. 
(a)  Lot # 11-137 
(b)  Lot # 11-170  
Figure 2-5. 
Multi-Ply-plated steel 5-cent nonsense pieces struck at 54 tonnes.  
62  

The three copper-based alloys designed to be seamless replacements for cupronickel all had good 
coinability; showing complete coin fill at nominal press loads – see Figure 2-6.  Each nonsense 
piece had an attractive appearance, but G6 mod and 669z displayed a slight yellow cast.  The 
color cast was reduced during striking, but returned once the nonsense pieces were exposed to the 
atmosphere for several days.  The nickel-plated 31157 nonsense piece was found to have a shinier 
white color than incumbent cupronickel 5-cent coins.  Alloys were obtained from Olin Brass (G6 
mod), PMX Industries, Inc. (PMX) (669z) and JZP (nickel-plated 31157). 
(a)  G6 mod 
(b)  669z 
Figure 2-6. 
Copper-based alloys G6 mod, 669z and nickel-plated 31157 5-cent nonsense 
pieces struck at 50–54 tonnes. 
(c) Nickel-plated 31157 
Grade 302HQ stainless steel from Carpenter Technology required a higher striking load and did 
not achieve acceptable edge fill at the highest allowable press load.  Two different annealing heat 
63  

treatments were tested to determine if improved coin fill could be achieved at lower striking 
loads.
51 
Despite a 4% difference in measured hardness, the two variants did not show substantial 
differences in coin fill, as seen in Figure 2-7. 
Commercial-off-the-shelf 430 stainless steel, purchased from a warehouse, displayed poor 
coinability.
52 
Note the poor fill in the lettering near the rim as shown in Figure 2-8.  The 
material’s high hardness, reflected in a Rockwell 15T hardness of 88, caused fill and dimensions 
to be inadequate at a high striking load of 70 tonnes. 
Figure 2-7. 
302HQ stainless steel 5-cent nonsense pieces struck at 70 tonnes. 
(a)  
Standard anneal – blanked at CTC 
(b)  Alternative anneal – blanked at 
Carpenter Technology 
Figure 2-8. 
430 stainless steel 5-cent nonsense piece struck at 70 tonnes. 
51 
Lower striking loads reduce die striking stresses resulting in a reduced rate of die fatigue damage and thereby  
achieve longer die life.
52 
The pedigree of the 430 stainless steel was not provided and therefore it is unknown.  
64  

2.4.3.3  Quarter Dollar Nonsense Pieces 
A few factors limited the selection of alternative materials for the quarter dollar candidate 
materials.  Some of the producers could not provide starting stock in the desired gage for quarter 
dollar alternative material candidates in time for Round One striking trials.  In addition, roll 
cladding of G6 mod or 31157 onto a C110 copper core could not be accomplished in time for 
these striking trials.  CTC was able to obtain 669z roll clad to C110 from PMX and Multi-Ply­
plated steel from the Royal Canadian Mint.  The Multi-Ply-plated steel planchets were 
specifically designed to have a unique electromagnetic signature
53 
(EMS) based on a database 
available at the RCM of such signatures for coins throughout the world.  Figure 2-9 shows a 
nonsense piece produced from 669z-clad C110.  This material candidate struck to a finished 
appearance comparable to the incumbent cupronickel-clad quarter dollar coin.  The Multi-Ply­
plated steel nonsense pieces showed good detail as seen in Figure 2-10. 
Figure 2-9. 
669z-clad C110 quarter dollar nonsense piece struck at 62 tonnes. 
53 
Electromagnetic signature (EMS) is understood in the industry to mean the electrical signal strength of a nearby 
electromagnetic sensor as a coin passes in close proximity to the sensor.  The magnetic field in the vicinity of the 
emitting sensor, and therefore the electrical current in the EMS receiving sensor, changes as the coin passes by.  The 
change in electrical signal strength is influenced by the materials of construction along with the thickness and 
distribution of materials within the coin.  The signal strength and/or its decay rate are then used by software to 
validate the coin and determine its denomination.  One key determiner of EMS is electrical conductivity. 
65  

Figure 2-10.  Multi-Ply-plated steel quarter dollar nonsense piece struck at 62 tonnes. 
2.4.4  Phase 4 Post Str iking Tr ial Testing – Round One 
Two-hour steam corrosion tests were performed on the as-struck nonsense pieces.  Total color 
vector change values were calculated from the spectrophotometer measurements taken before and 
after exposure.  No comparable tests were performed on incumbent materials using the nonsense 
striking dies; therefore values from steam corrosion testing of unstruck planchets are included in 
Tables 2-25 through 2-27 for comparison.  In general, nonsense pieces with a copper-based 
exterior had higher total color vector change readings that those with nickel surfaces; the 
magnitude of total color vector changes for other surfaces were typically between the extreme 
values represented by the copper-based and nickel-based materials.  In general, stainless steel had 
very low steam corrosion total color vector change readings, although the 302HQ blanked by 
Carpenter Technology
54 
had a distinct oxide coating due to a non-optimized heat treatment.  This 
undesirable oxide appeared to react to the low-pressure steam with a visible color change. 
Wear test results are also shown in Tables 2-25 through 2-27.  Nominally, the total weight loss in 
the wear test should not exceed 2% of the original weight according to United States Mint’s test 
procedures.  Several of the alternative material candidates met this criterion, while others showed 
wear beyond 2% after only 309 hours of testing.  In the case of Al-Mg alloy 5052-H32 and Dura­
White-plated zinc specimens, the excessive wear could be correlated with testing a mixture of 
different materials at the same time.  Materials were grouped for the wear tests by hardness:  those 
with low hardness were placed in one test container; all other samples were placed in a second 
test container for this round of wear testing.  Performing tests on mixed batches of materials does 
give some insight into possible wear rates during co-circulation of incumbent coins and those 
made of the alternative material candidates. 
Wear testing during the course of this project was problematic.  Test results proved to be 
inconsistent, particularly for some materials that were subject to galvanic corrosion, depending on 
the precise mix of different nonsense pieces being tested.  Performing wear tests with a specific 
54 
Due to lack of proper blanking equipment, Carpenter Technology cut blanks with either a waterjet cutter or a wire 
electro-discharge machine (EDM). 
66  

candidate material by itself typically provided different results than when wear tests were 
completed with mixed materials.  While the wear test was developed to include several commonly 
encountered wear mechanisms in a single test, i.e., rubbing against cloth, leather and cork 
materials in a simulated sweat solution to simulate different usage conditions, it is a difficult test 
to perform in a well-controlled manner so as to ensure consistent results.  The detailed chemistry 
of actual sweat varies considerably from one individual to another, for example.  The wear test 
results should be taken as a qualitative indication of potential fitness of a candidate material, and 
small variations should not be interpreted to represent reproducible differences.  Using the United 
States Mint’s wear test procedure, the alternative materials can be judged as ‘better than’, 
‘approximately equivalent to’ or ‘worse than’ incumbent materials, but no confident prediction of 
a service lifetime can be made based on the results of this wear test procedure. 
Accelerated corrosion of certain materials occurs when contact between them leads to galvanic 
corrosion.  Dissimilar metals that are simultaneously in contact with one another and a conductive 
solution (such as artificial sweat) act like a battery, leading to rapid chemical attack of the anodic 
element of the couple.  When aluminum- and tin-plated materials were tested along with other 
types of coins containing copper or cupronickel in the artificial sweat solution, the aluminum- and 
tin-plated materials appeared to wear rapidly.  This rapid wear was due to a chemical reaction that 
was dissolving the metal leading to significant weight loss.  Subsequent testing of these materials 
in isolation (see Round Two wear results) shows that they are not particularly susceptible to 
normal rubbing and sliding wear.  Co-circulation with copper-based coins is of concern for the 
aluminum- and tin-plated alternative material candidates. 
As described above, Round One wear testing was performed with materials being mixed 
according to hardness.  It is believed that due to galvanic corrosion between the various materials, 
all the alternative material candidates can be judged as having worse wear characteristics than the 
incumbent materials.  The only alternative material candidate providing better wear characteristics 
than the incumbent material; was 302 stainless steel for the 5-cent coin. 
Table 2-25. 
Post Striking Steam Corrosion and Wear Test Results for One-Cent Coin  
Alternative Material Candidates – Round One  
Material 
Steam Corrosion (Total 
Color Vector Change) 
Wear Test (% Weight 
Change) 
139 hours 
309 hours 
Copper-Plated Zinc (Incumbent Material) 
5.5 
–0.19 
–0.89 
Aluminized Steel (Ryerson) 
10.0 
–1.0 
--* 
Aluminized Steel (Atlas) 
7.7 
–0.9 
–12.6 
Al-Mg Alloy 5052-H32 
4.9 
–1.3 
–6.3 
Copper-Plated Steel 
14.9 
–0.67 
–3.3 
430 Stainless Steel 
N/A** 
N/A 
N/A 
* Removed from testing early due to rapid and excessive weight loss in excess of 2%.  
** Grade 430 stainless steel was not successfully coined.  
Note:  Weight loss of all alternative material candidates is above 2% after 309 hours.  
67  

Table 2-26. 
Post Striking Steam Corrosion and Wear Test Results for 5-Cent Coin Alternative  
Material Candidates – Round One  
Material 
Steam Corrosion (Total 
Color Vector Change) 
Wear Test (% Weight 
Change) 
139 hours 
309 hours 
Cupronickel (Incumbent Material) 
4.7 
–0.12 
–0.23 
Dura-White-Plated Zinc 
2.7 
–1.8 
–10.5 
Multi-Ply-Plated Steel (Lot # 11-137) 
0.9 
–0.10 
–0.67 
Multi-Ply-Plated Steel (Lot # 11-170) 
0.7 
–0.07 
–0.46 
G6 Mod 
7.1 
–0.26 
–0.63 
302HQ Stainless Steel (blanked at CTC)* 
0.8 
N/A 
N/A 
302HQ Stainless Steel (blanked at 
Carpenter Technology) 
3.0 
–0.03 
–0.08 
430 Stainless Steel** 
0.4 
N/A 
N/A 
669z 
6.0 
–0.28 
–0.64 
Nickel-Plated 31157 
0.7 
–0.12 
–0.46 
* 302HQ stainless steel blanked at CTC was not wear tested.  Material from Carpenter Technology was expected to 
provide comparable wear.  
** Grade 430 stainless steel was not successfully coined.  
Table 2-27. 
Post Striking Steam Corrosion and Wear Test Results for Quarter Dollar Coin 
Alternative Material Candidates – Round One