Final report

Dura-White-Plated Zinc 
(variant) 
Copper Thickness (micron) 
Tin Thickness 
(micron) 
12-5 
12.0 
5.0 
12-8 
12.7 
7.7 
11-10 
11.2 
10.2 
*Thickness measured at the center of the obverse and reverse.  Each datum is the mean of six measurements. 
The three Dura-White-plated zinc variants struck well at 54 tonnes, but surface appearance looked 
better at 62 tonnes.  United States Mint engineers advised striking the three variants at 54 tonnes 
because dimensional targets were met at the lower load.  This load is lower than the 62 tonnes 
used for volume production of the incumbent quarter dollar coins.  The surface color was slightly 
duller and grey-white relative to the incumbent 5-cent coin as shown in Figure 2-24. 
(a)  Variant 12-5 
(b)  Variant 12-8 
(c)  Variant 11-10  
Figure 2-24.  Dura-White-plated zinc quarter dollar nonsense pieces struck at 54 tonnes.  
Roll-clad 669z on C110 strip was designed to provide an EMS match with the incumbent quarter  
dollar coin.  The material struck very well at nominal press loads of 62 tonnes – see Figure 2-25.  
81  

Figure 2-25.  669z-clad C110 quarter dollar nonsense piece struck at 62 tonnes. 
(a)  Obverse 
(b)  Reverse 
Although neither of the other two copper-based alloys, i.e., G6 mod and unplated 31157, 
evaluated for the 5-cent coin were roll clad onto C110 and then tested during any striking trials, 
CTC has confidence from the 5-cent coin striking trials and from the compositions of these alloys 
that roll cladding to C110 can be successfully accomplished.  Verification should be completed 
before committing to these materials for future quarter dollar coins. 
To be consistent with the weight of incumbent quarter dollar coins, the nickel-plated steel quarter 
dollar planchets from the Royal Mint were approximately 10% thicker than the United States 
Mint planchet specifications for incumbent coins.  These planchets also had a larger rim profile 
than incumbent quarter dollar planchets.  The increased amount of material at the edge of the 
planchet allowed for early fill of the edge of the die; after the edge features were filled, resistance 
to additional deformation inhibited material flow into the central design features as seen in Figure 
2-26.  The striking trial for this material was performed at 65 tonnes to achieve good fill; 
however, it is speculated that properly sized planchets might require less tonnage to achieve 
comparable appearance and dimensional precision.  Note that Figure 2-26 shows the nonsense 
piece at 62 tonnes. 
82  

Figure 2-26.  aRMour quarter dollar nonsense piece struck at 62 tonnes. 
(a)  Obverse 
(b)  Reverse 
In summary, with the exception of 302HQ stainless steel, all of the quarter dollar coin alternative 
material candidates could produce acceptable circulating coins if the striking load was sufficiently 
high (but within the safe operating limits of the current presses and dies) and the planchet rim was 
of optimum size.  The striking load required to attain good coin fill for 302HQ stainless steel was 
higher than could be safely completed on existing United States Mint production presses.  In 
CTC’s opinion, this alloy still shows promise as a candidate material, but only after added alloy 
development demonstrates the viability of the material. 
2.4.9  Phase 4 Post Tr ial Testing – Round Two 
2.4.9.1  Steam Corrosion and Wear Testing 
Steam corrosion and wear tests were conducted on nonsense pieces struck during Round Two 
striking trials.  Nonsense pieces from each alternative material candidate were subjected to the 
two-hour steam corrosion test.  Results of the testing are summarized in Tables 2-32 through 2­
34. 
Steam corrosion testing of one-cent nonsense pieces showed copper-plated materials experienced 
the largest change in color, with the familiar darkening to deeper brown shades.  Both the 
aluminum and stainless steel nonsense pieces showed less color change.  For 5-cent candidate 
materials, the nickel-plated (including Multi-Ply), tin-plated (i.e., Dura-White) and stainless steel 
nonsense pieces showed only small changes in color.  The other 5-cent alternative material 
candidates (all copper-based alloys) displayed color changes essentially equivalent to the 
incumbent cupronickel material.  Color change, resulting from steam corrosion testing, of all but 
one of the quarter dollar candidate materials were similar to or better than the incumbent material; 
669z-clad C110 demonstrated a marginally worse color change than the incumbent quarter dollar 
material. 
Deviations were made to the United States Mint’s wear procedure for the CTC tests.  Preliminary 
wear testing showed a steady increase in weight loss with time.  The results followed a smooth 
and predictable trend.  There was no indication of sudden changes that would reorder the relative 
ranking of one material with respect to others after a two-week test.  The wear test results should 
be taken as a relative indication of potential fitness of a candidate material.  It is CTC’s opinion 
83  

that small variations probably do not represent reproducible and consistent differences.  The 
candidate materials can be judged as ‘better than’, ‘roughly equivalent to’ or ‘worse than’ 
incumbent materials, but no confident prediction of a service lifetime appears to be possible based 
on the results of the United States Mint’s wear test procedure. 
As discussed in Section 2.4.4 concerning Round One wear testing of mixed materials and the 
associated galvanic corrosion affecting the results, Round Two wear testing was split into two 
groups.  Group One wear testing isolated the materials as much as possible in order to eliminate 
any galvanic corrosion affects.  Group Two was performed while isolating Dura-White nonsense 
pieces with only incumbent circulating coinage materials.  This condition was deemed to 
represent a normal co-circulation situation if Dura-White coins were to be introduced into 
circulation.  Group One wear results are discussed in this section while Group Two results are 
discussed in Section 2.4.9.2. 
Wear for all Group One alternative material candidates was no worse, and in some cases was 
considerably better, than the incumbent materials for all Round Two alternative material 
candidates for all three denominations tested.  All of the alternative material candidates would be 
acceptable from the standpoint of wear.  Note that Dura-White-plated zinc and Al-Mg alloy 5052­
H32 nonsense pieces were tested in isolation for Round Two.  Each showed good inherent wear 
resistance in this test.  Appendix 2-F contains photographs of test specimens after wear testing. 
Color changes and wear patterns can be compared in the photographs.  Note that 1) some color 
effects are related to the materials from other samples in the test, 2) some surface corrosion can be 
induced by the surrounding materials and 3) material could be transferred from softer to harder 
materials, affecting the surface color and wear. 
Table 2-32. 
Round Two Post Striking Trial Test Results – One-Cent Nonsense Pieces 
Material 
Steam 
Corrosion 
Wear (% weight change at 
specified time) 
Total Color 
Vector Change 
120 hours 
380 hours 
Copper-Plated Zinc 
(Incumbent Material) 
6.6 
–1.4 
–3.4 
Al-Mg Alloy 5052-H32 
1.8 
–0.2 
–0.3 
Copper-Plated Steel – RM 
11.2 
–1.1 
–1.5 
Copper-Plated Steel – JZP 
6.5 
–1.0 
–1.4 
302HQ Stainless Steel 
2.8 
0 
0 
84  

Table 2-33. 
Round Two Post Striking Trial Test Results – 5-Cent Nonsense Pieces 
Material 
Steam 
Corrosion 
Wear (% weight change at 
specified time) 
Total Color 
Vector Change 
120 hours 
380 hours 
Cupronickel (Incumbent 
Material) 
4.4 
–0.5 
–0.8 
Nickel-Plated Steel 
2.8 
–0.2 
–0.4 
Unplated 31157 
5.5 
–0.2 
–0.4 
Multi-Ply-Plated Steel 
1.3 
–0.2 
–0.5 
Dura-White-Plated Zinc 
1.4 
–0.1 
–0.6 
669z 
5.1 
–0.4 
–0.7 
G6 Mod 
4.0 
–0.4 
–0.7 
302HQ Stainless Steel 
1.5 
0 
0 
Table 2-34. 
Round Two Post Striking Trial Test Results – Quarter Dollar Nonsense Pieces 
Material 
Steam 
Corrosion 
Wear (% weight change at 
specified time) 
Total Color 
Vector Change 
120 hours 
380 hours 
Cupronickel-Clad C110 
(Incumbent Material) 
4.5 
–1.0 
–4.7 
Nickel-Plated Steel 
3.3 
–0.2 
–0.4 
Multi-Ply-Plated Steel 
3.6 
–0.3 
–0.5 
302HQ Stainless Steel 
4.4 
0 
0 
669z-Clad C110 
6.5 
–0.4 
–0.9 
Dura-White-Plated Zinc 
1.9 
–0.1 
–0.2 
2.4.9.2  Additional Round Two Wear Testing 
Wear testing during the course of this project was problematic.  Test results proved to be 
inconsistent at times, particularly for some materials that were subject to galvanic corrosion, 
depending on the composition of the mix of different nonsense pieces being tested within the 
same batch.  Performing wear tests with a specific alternative material candidate by itself often 
provided significantly different results than with wear tests of mixed materials.  To gain further 
insight into this phenomenon, an additional wear test was performed concentrating specifically on 
Dura-White nonsense pieces being mixed with incumbent circulating coinage materials, a 
situation deemed to represent a typical co-circulation scenario if Dura-White coins were to be 
introduced into circulation. 
Standard wear tests were conducted in two test chambers, one containing incumbent coinage 
materials only, and one with mixed Dura-White and incumbent materials.  Table 2-35 shows the 
results of these wear tests, compared with selected earlier wear test results.  Dura-White 5-cent 
nonsense pieces were wear tested in Round One (mixed with other materials), in Round Two 
(isolated with other Dura-White nonsense pieces in one test chamber) and mixed with incumbent 
coinage for this additional wear test.  Dura-White quarter dollar nonsense pieces were wear tested 
in Round Two and also during this additional wear test.  Results from corresponding one-cent, 5­
85  

cent and quarter dollar incumbent materials are reported in Table 2-35 in planchet form, after 
striking and tested without other metal alloys (isolated), and combined with Dura-White test 
materials (mixed). 
Table 2-35. 
Round Two Post Striking Trial Wear Test Comparison 
Material 
Sample 
Condition* 
Wear (% weight change at specified 
time) 
24 hours 
320 hours 
650 hours 
Copper-Plated Zinc 
(Incumbent One-Cent 
Material) 
Planchet 
–0.02 
–0.88 
–4.76 
Isolated 
–0.61 
–3.22 
–4.17 
Mixed 
–0.33 
–3.59 
–7.35 
Cupronickel (Incumbent 
5-Cent Material) 
Planchet 
–0.02 
–0.25 
–0.33 
Isolated 
–0.28 
–1.18 
–1.36 
Mixed 
–0.12 
–0.89 
–1.04 
Cupronickel-Clad C110 
(Incumbent Quarter Dollar 
Material) 
Planchet 
–0.05 
–0.31 
–0.88 
Isolated 
–0.29 
–0.80 
–1.08 
Mixed 
–0.13 
–0.40 
–1.10 
Dura-White-Plated Zinc 
(5-Cent Nonsense Pieces) 
Round One 
Mixed 
–0.10 
–10.5 
N/A 
Round Two 
Isolated 
–0.02 
–0.55 
N/A 
Round Two 
Mixed 
–0.15 
–1.67 
–4.13 
Dura-White-Plated Zinc 
(Quarter Dollar Nonsense 
Pieces) 
Round One 
Mixed 
N/A 
N/A 
N/A 
Round Two 
Isolated 
–0.01 
–0.16 
N/A 
Round Two 
Mixed 
–0.22 
–1.17 
–1.98 
*Coins/nonsense pieces placed in the wear test:  planchet – as stated; isolated – after striking and with no other 
metals; mixed – wear tested with other materials. 
Several comments can be made about these wear test results.  The relatively smooth planchets 
typically (but not always) wear less quickly than struck pieces, which have raised design features. 
The somewhat surprising result is the high wear rate observed for the copper-plated zinc nonsense 
pieces when tested ‘mixed’ with Dura-White materials.  Copper and nickel have relatively similar 
corrosion potentials, tin would selectively corrode in the presence of either copper or nickel. 
Hence the substantial increase in wear rate for the mixed tests cannot readily be explained.  The 
Dura-White surfaces certainly show higher wear rates in the presence of other materials.  The 
mixed wear testing shows large differences between 5-cent and quarter dollar nonsense pieces and 
between Round One mixed test and the Round Two mixed test.  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 controlled manner so as to ensure 
consistent results. 
86  

2.4.10  Phase 4 Coin-Pr ocessing Equipment Testing – Round Two 
Lots consisting of 100 nonsense pieces of each alternative material candidate and incumbent 
material, in addition to incumbent circulating coinage were sent for drop testing to three 
manufacturers of coin-processing equipment:  Coinco, MEI and SCAN COIN.  Details of these 
drop tests are given in the Outreach Chapter.  A summary of these results is presented here for 
completeness of the present chapter on material testing. 
All one-cent coin alternative material candidates from Round Two striking trials were 
characterized as having different EMS than the incumbent one-cent coins.  The EMS of CPS 
nonsense pieces was similar to many other coins in use throughout the world.  However, fraud is 
not considered a significant issue with low-value coins.
59 
Interestingly, the two coin-processing 
equipment manufacturers that provided recommendations on low-value coin material selections 
preferred plated-steel alternatives to the other candidate materials.  They cited low cost and 
minimal security needs in their rationale for recommending plated-steel coins.  The low density of 
aluminum as an alternative material candidate did cause coin-acceptance equipment jamming 
problems, and was therefore strongly discouraged by all the manufacturers; all three coin-
processing equipment manufacturers have experienced problems with aluminum coins used in 
their equipment within other countries. 
The 5-cent coin alternative material candidates drop test results fell into two categories.  The 
copper alloy alternative materials closely matched the EMS of the incumbent cupronickel coins. 
Two of the three manufacturers did not detect any EMS difference between the incumbent 5-cent 
coin and any of the 5-cent nonsense pieces made of 669z, G6 mod or unplated 31157.  The third 
manufacturer, however, did detect EMS differences between the incumbent 5-cent coin and both 
the G6 mod and 669z nonsense pieces; no detectable differences were observed by this 
manufacturer between incumbent 5-cent coins and the unplated 31157 nonsense pieces.  Alloy 
669z nonsense pieces had a low rate of acceptable (i.e., indistinguishable) matches with 
incumbent 5-cent coins; G6 mod consistently failed to be accepted during drop tests at this third 
coin-processing equipment manufacturer.  It is speculated that minor changes to alloy 
composition, rolling practices and/or heat treatment may sufficiently change the EMS 
characteristics so that a later generation of these alloys would result in 5-cent coins that would 
correctly validate in the devices made by this third manufacturer using the currently fielded 
equipment settings.  Doing so would avoid the need for changes to fielded units should one of 
these alternative material candidates be used in future US circulating coins.  Determination of 
precise measures required to improve the EMS of these copper-based alloys would be an 
appropriate topic for future research and development. 
The second category of alternative 5-cent materials consisted of those with distinctly different 
EMS than the incumbent cupronickel 5-cent coin; this category includes Multi-Ply- and nickel-
plated steels and Dura-White-plated zinc.  The plated-steel nonsense pieces exhibited a relatively 
large piece-to-piece variation in properties, which is commonly seen with plated-steel coins [7]. 
More problematic, however, is the fact that one of the coin-processing equipment manufacturers 
has sensors that cannot be adjusted to accept ferromagnetic-based coins.  Use of the 
ferromagnetic-steel-based alternative material candidates evaluated for the 5-cent (or any other) 
59 
Although no clear definition has been offered to define the transition in value from a low-value to a high-value 
coin, experts in the field typically place the transition at about 25 cents. 
87  

coin would require development of a new sensor and a major upgrade for each of the fielded units 
from this manufacturer.  The Dura-White-plated zinc nonsense pieces had notably consistent 
EMS readings.  These EMS readings were clearly unique and distinguishable from other coins 
throughout the world.  The plated alternative material candidates differ in their EMS from 
incumbent coins; therefore, coins made of these alternative material candidates would require that 
EMS-based coin-processing equipment owners and operators acquire software/hardware upgrades 
for existing machines. 
The quarter dollar nonsense pieces showed similar trends as the 5-cent alternative material 
candidates.  The 669z-clad C110 nonsense pieces were indistinguishable, according to all three 
coin-processing equipment manufacturers, from incumbent circulating quarter dollar coins.  Note 
that although the other two copper alloys, G6 mod and unplated 31157, were not tested in the 
clad-copper configuration, CTC expects that all three copper-based alloys clad to C110 would 
perform in a similar fashion relative to EMS. 
Each plated-steel nonsense piece had a distinctly different EMS than incumbent cupronickel-clad 
C110 quarter dollar coins; however, the EMS of nickel-plated steel quarter dollar coin was found 
to be similar to many other plated-steel circulating coins used around the world.  As with other 
plated-steel nonsense pieces, the EMS readings of plated-steel quarter dollar nonsense pieces 
exhibited a relatively large piece-to-piece variation in properties, which is common with plated-
steel coins.  The Dura-White-plated zinc coins demonstrated an EMS that was clearly unique and 
distinguished from other coins throughout the world.  The Dura-White-plated zinc nonsense 
pieces also had the most narrowly observed EMS readings of all material-denomination 
combinations that were tested. 
2.4.11  Alter native Coatings 
Appendix 2-G shows results from surface-modified zinc materials.  The purpose of these trials 
was to determine the long-term potential of modifying the color of one-cent coins to eliminate the 
need for copper plating while maintaining the color of incumbent one-cent coins.  Before the 
United States Mint can incorporate surface-modification technology into coinage production, a 
significant amount of additional development needs to be completed.  Also shown in Appendix 2­
G are results from early trials of nickel coatings deposited by the carbonyl process.  This process 
also requires significant development before it can be used in production of circulating coins. 
The early trials conducted in this study suggest that the carbonyl process should be considered for 
a more thorough evaluation and development for potential future application in the production of 
US circulating coins. 
2.5 
CONCLUSIONS 
̄ CHAPTER 2 
̄ 
Test results for the one-cent coin alternative material candidates are summarized in Table 2-36. 
These results demonstrate that several potential alternative material candidates could be used for 
future one-cent coins although further development and testing are needed to ensure production 
viability, consistent performance in coin-processing equipment and general acceptance by the 
public.  In particular, stainless steels that have not been specifically developed to have very low 
strength/hardness cannot be struck effectively under current conditions of die profile and 
equipment capability at the United States Mint.  Results of striking trials using commodity 
88  

“aluminized” steels were unsatisfactory.  Specially processed steels, like those used for the 
copper-plated steel tested for this study, did exhibit good coinability. 
For one-cent coins, which are rarely used in vending machine commerce, but are routinely 
processed through coin sorters and counters, security is not a significant issue due to their low 
value.  These coins must feed reliably through coin-handling equipment and should not jam or be 
misvalidated as another coin if mistakenly inserted into any coin-processing device.  The low 
weight of aluminum one-cent nonsense pieces did cause coin-processing machine jamming 
problems, and was strongly discouraged by all manufacturers of coin-processing equipment.  The 
combined test results indicate that copper-plated steel is the leading alternative metallic material 
to replace the incumbent copper-plated zinc used in one-cent coins.  Of course, other factors 
discussed in the other chapters of this report must also be considered before any decision is made 
to change materials of construction for the US one-cent circulating coin. 
Table 2-36. 
Performance Test Results of One-Cent Coin Alternative Material Candidates 
Material 
Color 
Striking 
Load 
(tonne)