Lead Alloy Grid Composition for Corrosion Resistance
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Solution Overview
Problem
Current lead-acid battery grid alloys face challenges in maintaining mechanical properties, corrosion resistance, and preventing thermal runaway, especially in deep discharge-charge cycling regimes, while also dealing with environmental concerns from cadmium-containing alloys and the high cost of silver-based alternatives.
Innovation Solution
A lead-based alloy with specific compositions of tin, calcium, bismuth, and copper is developed, which provides enhanced mechanical properties, improved corrosion resistance, reduced gassing, and lower sulfation, eliminating the need for post-casting treatments and offering better performance than existing alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous direct casting process is used to manufacture grids, then manufacturing efficiency and economy are improved, but corrosion resistance deteriorates due to oriented grains creating shorter intergranular paths
Solution Approach 1:
The patent modifies the chemical composition parameters of the lead alloy by adding specific amounts of bismuth (0.01-0.05 wt%), tin (0.5-2.0 wt%), and calcium (0.01-0.1 wt%), which changes the corrosion behavior and grain structure of the alloy, thereby improving corrosion resistance while maintaining the continuous casting process
Solution Approach 2:
The patent creates a composite alloy system by combining lead with multiple alloying elements (bismuth, tin, calcium, copper, silver), where each element contributes specific properties that collectively enhance corrosion resistance and mechanical properties while allowing continuous casting
2Strength
If cadmium-containing alloys are used to improve mechanical properties and corrosion resistance, then grid strength is improved, but environmental harm increases
Solution Approach 1:
The patent removes cadmium from the alloy composition entirely and replaces it with environmentally friendly alternative elements (bismuth, tin, calcium), thereby eliminating the harmful environmental effects while maintaining or improving the desired mechanical and corrosion resistance properties
Solution Approach 2:
The patent changes the chemical composition parameters by substituting toxic cadmium with non-toxic alternative elements in specific concentrations, transforming the alloy from harmful to environmentally friendly while preserving performance
3Reliability
If silver-based alloys are used to enhance corrosion resistance, then corrosion protection is improved, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the concentration parameters of alloying elements, using silver at low levels (0.01-0.1 wt%) combined with more cost-effective elements like bismuth and tin, thereby achieving the desired corrosion resistance at a lower overall cost than traditional silver-based alloys
Solution Approach 2:
The patent creates a multi-element composite alloy where silver works synergistically with other elements (bismuth, tin, calcium, copper), allowing reduced silver content while maintaining or enhancing corrosion resistance, thereby lowering manufacturing cost
4Duration of action of stationary object
If grid alloy undergoes corrosion during service life, then electrical conductivity decreases causing cell failure, but this is a natural degradation process
Solution Approach 1:
The patent modifies the chemical composition parameters of the grid alloy by adding elements that form more stable and conductive corrosion products, changing the corrosion mechanism itself to preserve electrical conductivity over time
Solution Approach 2:
The patent transforms the harmful corrosion process into a beneficial one by designing an alloy that forms protective, conductive corrosion products (such as calcium sulfate and stable lead oxides) that actually protect the grid and maintain conductivity, converting the degradation process into a protective mechanism
Data Source
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AI summary
A lead-acid battery grid made from a lead-based alloy containing tin, calcium, bismuth and copper and characterized by enhanced mechanical properties, corrosion resistance, less battery gassing, lower sulfation and water loss, and no post-casting treatment requirements for age hardening. In one embodiment, the battery grids are formed from a lead-based alloy including about 2.0% tin, about 0.0125% copper, about 0.065% calcium, and about 0.032% bismuth. Preferably, the battery grid is free of silver beyond trace levels in the alloy.