Lead-Acid Battery Grid Corrosion Resistance via Silver Alloying
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Solution Overview
Problem
Lead-calcium alloys used in lead-acid battery grids face challenges such as inadequate hardness, difficulty in handling, slow hardening, and increased corrosion at high temperatures, leading to premature battery failure and the need for costly curing processes to adhere pastes effectively.
Innovation Solution
A lead-based alloy with a silver concentration of 0.003 to 0.015 weight percent, subjected to mechanical deformation, resulting in a predominant equiaxed grain structure that enhances corrosion resistance and rapid hardening, allowing for the production of thin, durable grids without extensive aging or artificial processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-calcium alloys are used for positive grids, then corrosion resistance is improved, but hardness is insufficient and handling becomes difficult
Solution Approach 1:
The patent uses a composite alloy system combining lead-calcium-tin with small additions of silver (0.003-0.015 wt%) and other elements. This composite material approach allows the grid to achieve both corrosion resistance from the lead-calcium base and enhanced hardness from the synergistic effects of tin and silver additions, resolving the contradiction between these two properties.
Solution Approach 2:
The patent optimizes the chemical composition parameters within specific ranges: calcium (0.02-0.08 wt%), tin (0.3-1.8 wt%), and silver (0.003-0.015 wt%). By precisely controlling these parameter ranges, the alloy achieves the optimal balance between corrosion resistance and hardness, allowing the material to satisfy both requirements simultaneously.
2Productivity
If grids are made thinner to increase battery performance, then productivity and voltage are improved, but handling difficulty and corrosion resistance worsen
Solution Approach 1:
The enhanced alloy composition with optimized calcium, tin, and silver content provides superior corrosion resistance that enables the use of thinner grid sections. The composite material structure maintains integrity and resistance even at reduced thickness, allowing productivity improvement through thinner grids without sacrificing reliability.
Solution Approach 2:
The patent creates local quality enhancement at grain boundaries through silver segregation, which provides concentrated corrosion protection at critical locations. This localized strengthening allows the overall grid to be made thinner while maintaining sufficient corrosion resistance in the thinner sections.
3Strength
If lead-antimony alloys are used, then hardness and handling are improved, but corrosion resistance deteriorates due to antimony release
Solution Approach 1:
The patent replaces the lead-antimony composite system with a lead-calcium-tin-silver composite system. This substitution eliminates the harmful antimony release while maintaining the desired hardness through tin and silver additions, achieving both mechanical strength and corrosion resistance without the detrimental effects of antimony migration.
4Temperature
If rapid cooling is applied to thin grids, then temperature control is improved, but mechanical deformation increases due to inadequate hardness
Solution Approach 1:
The patent applies preliminary alloying with specific additions of tin and silver before the cooling process. These pre-added elements ensure that the material has sufficient hardness and mechanical strength before rapid cooling occurs, preventing deformation during the temperature reduction process while still allowing rapid cooling to be applied for productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The alloy provides improved corrosion resistance, rapid hardening, and enhanced mechanical properties, enabling the production of thin grids that can withstand high temperatures and maintain active material retention, reducing premature battery failure and handling issues.
Implementation Method 1
the concentration of silver is sufficient to stabilize a significant portion of said grain boundaries such that the corrosion resistance of the alloy tends to be better
Implementation Method 2
the lead-based alloy comprises silver and is subjected to mechanical deformation to increase the number, amount, or density of grain boundaries
Data Source
AI summary
A process of preparing a continuous cast lead-based alloy strip for use in the manufacture of a battery grid of a lead-acid battery, the process comprising mechanically deforming, at a deformation temperature in a range of about 15 to about 150° C., a continuous cast lead-based alloy strip having a thickness of tcast that is in a range that is from about 0.6 to about 2 mm to reduce the thickness of the strip to a thickness of treduced that is in a range that is from about 0.4 to about 1.5 mm such that the reduction in thickness is in a range of about 10 to about 50%, wherein the lead-based alloy comprises lead and silver and is essentially free of calcium, and wherein the silver is at a concentration that is in a range of about 0.003 to about 0.015 weight percent.