Coins as Dive Weights: Pioneering Lead-Free Diving

In our mission to eliminate toxic lead from diving, we found a solution hiding in plain sight: coins. This extensively researched approach transforms everyday currency into effective dive weights, proving that sustainable diving can be both accessible and practical. While precision-crafted stainless steel weights remain the gold standard for performance and longevity, coin-based weights offer an immediate path for divers to join the movement toward lead-free diving. Our analysis reveals how specific coins, particularly those made from marine-grade cupronickel alloys, can provide reliable weighting while eliminating the environmental and health risks associated with traditional lead weights.

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Split image: traditional lead weights vs coin weights

Why Consider Coins?

Unlike purpose-made weights, coins provide unique advantages in recyclability and recovery incentive. If lost during a dive, coins retain their monetary value, encouraging retrieval. More importantly, they can always return to circulation as currency, exemplifying true circular economy principles. This stands in stark contrast to lead weights, which require specialized recycling facilities and often end up abandoned in marine environments.

Circular economy diagram

Material Science: Understanding Coin Alloys

Modern coins utilize sophisticated alloys that often surpass traditional dive weight materials in corrosion resistance. The following table compares common coin materials with conventional dive weight options:

Alloy Type Density (g/cm³) Corrosion Rate (mm/year) † Seawater Stability Toxicity Risk
Lead (Reference) 11.3 0.02-0.56 ★★ High
304 Stainless Steel (Reference) 8.0 0.01-0.02 ★★★ Low
316 Stainless Steel (Reference) 8.0 0.002-0.01 ★★★★★ Low
Aluminum-Bronze (92Cu-6Al-2Ni) 8.5 0.02-0.07 ★★★★ Low
Cupronickel (75Cu-25Ni) 8.9 0.02-0.05 ★★★★ Low
Nickel-Brass (75Cu-20Zn-5Ni) 8.6 0.02-0.08 ★★ Low
Nordic Gold (89Cu-5Al-5Zn-1Sn) 8.7 0.08-0.12 ★ Low

† References for alloy corrosion rates in sea water:

A key measure of how well a material will survive in the ocean is the corrosion rate. While there are many published measures of corrosion rate available, it can be confusing because corrosion depends on the salinity, pH, agitation, flow rate, temperature, and abrasion. For a granular dive weight in particular, the mechanical stability of the corrosion layer is key because granular dive weights are constantly shifting and adjusting as the diver moves. As a result, a material with a weaker corrosion layer such as lead will experience the fastest corrosion.

A further factor that affects corrosion rate is geometry. In general, an object with less surface area will degrade slower. Thus a small coin or lead shot will degrade much faster than a monolithic weight such as a dive steel weight or lead belt weight.

Key Alloy Characteristics:

Aluminum-Bronze: Found in some Australian and British coins, this alloy combines good corrosion resistance with high strength. Its aluminum content forms a protective oxide layer, while copper provides necessary density.

Cupronickel: Used in U.S. nickels, this copper-nickel alloy offers strong corrosion resistance at a lower cost point. Its proven marine performance makes it a practical choice for diving applications.

Nordic Gold: A copper-based alloy used in Euro coins, offering moderate corrosion resistance while maintaining an attractive appearance.

Nickel-Brass: Common in higher-denomination coins worldwide, this alloy provides moderate corrosion resistance with excellent wear characteristics.

Stainless steel: Rarely used as coins, but showa some of the best overall corrosion resistance. However it can experience pitting corrosion if salt water is allowed to dry on it.

Lead: Not suitable for coins due to toxicity, mechanical weakness. Good corrosion resistance, but passive surface is easily mechanically damaged.

Global Coin Comparison

Nation Coin Type Value Alloy 4lb Qty USD Cost Bulk Notes
🇺🇸 USA Nickel $0.05 Cupronickel 363 $18.15 Moderate Most cost-effective readily available option
🇦🇺 Australia 2 Dollar $2.00 Aluminum-Bronze 275 $357.00 Low-Moderate Good corrosion resistance
🇲🇽 Mexico 10 Peso 10 MXN Aluminum-Bronze (Ring) 176 $103.00 Low Bi-metallic construction, most compact option
🇪🇺 Euro Zone 2 Euro €2.00 Nickel-Brass/Core 214 $467.00 Low-Moderate Sophisticated bi-metallic design
🇯🇵 Japan 500 Yen ¥500 Nickel-Brass 260 $867.00 Moderate Special anti-corrosion plating
🇬🇧 UK 1 Pound £1.00 Nickel-brass (Ring) 280 $356.00 Low-Moderate Bi-metallic construction
🇵🇰 Pakistan 5 Rupee Rs.5 Cupronickel 404 $7.40 High Lowest theoretical cost, but hard to source
🇵🇭 Philippines 5 Peso ₱5 Cupronickel 252 $16.80 Moderate Good weight-to-value ratio but limited availability

Analysis reveals interesting patterns across global currencies. The U.S. nickel presents a compelling alternative dive weight, offering excellent marine stability at remarkably low cost—just $18.15 for a 4 pound weight. Note that this nickel weight is less expensive than most comparable lead weights, non-toxic, and retains its economic value. Globally there are many other cupronickel coins like the U.S. nickel and these will in general provide the best dive weights.

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The Australian 1 Dollar and 2 Dollar , crafted from aluminum-bronze, demonstrate good seawater stability. While their cost approaches $360 for a 4-pound set, their durability could justify the investment.

Bimetallic coins, zinc containing coins, and steel core coins are generally poor choices. These coins are subject to galvanic corrosion and would not last as long in sea water. However, even these coins could be used if they are used infrequently and care is taken to rinse and thoroughly dry the coins between uses.

Implementation and Usage

Coins can be used similarly to lead shot in soft weight systems, adapting easily to existing diving equipment. They can be housed in mesh bags, integrated belt pouches, or removable BCD weight pockets. Their granular nature allows precise weight adjustment and weight distribution around the diver's body.

To maximize longevity and maintain performance, proper coin care is essential. After each dive, rinse the coins thoroughly in fresh water to remove salt residue. Allow them to dry completely before storage, and keep them in a dry environment between dives. This simple maintenance routine significantly reduces corrosion risk and extends the useful life of the coin weights.

Implementation examples

A Way Beyond Traditional Lead Weights

The diving community often cites a lack of alternatives as justification for continued lead weight use. However, this analysis demonstrates that viable options exist using readily available materials. While Dive Steel offers precision-crafted stainless steel weights as one solution, coin-based weights represent another practical path forward.

Furthermore, coins can play a crucial role in our mission to eliminate lead from diving environments worldwide. Through our trade-in program concept, travelers can bring appropriate coin weights to remote diving locations and exchange them for operators' lead weights. This approach provides immediate value to operators while allowing divers to properly recycle the lead weights in their home countries. This exchange reduces lead exposure for dive operators, visiting divers, and marine environments while supporting local economies through the introduction of usable currency.

Consider this analysis not just as information, but as an invitation to action. Whether choosing premium stainless steel weights, assembling coin-based alternatives, or participating in weight exchange programs, every diver can contribute to eliminating lead from our oceans. The options exist—now we must choose to use them.

Trade-in program world map