I'm designing a heat exchanger for a solar thermal system and need to choose between copper and stainless steel for corrosion resistance in high-temperature water. What are the key factors to consider for long-term durability?

For a heat exchanger in a high-temperature water environment, stainless steel is often the better choice for corrosion resistance compared to copper. Here's a breakdown of key factors:

• Corrosion Mechanisms: Copper can suffer from pitting corrosion and dezincification in oxygenated water at high temps, while stainless steel (e.g., grade 316) resists this due to its chromium oxide layer.
• Material Properties: Consider factors like thermal conductivity (copper is higher, but stainless steel is adequate) and mechanical strength. Stainless steel offers better long-term stability in harsh conditions.
• Practical Example: In solar thermal systems, stainless steel is commonly used for components exposed to hot water to avoid leaks and maintenance issues. Copper might be used in lower-risk areas for cost savings.
• Resources: Check the ASM Handbook for detailed corrosion data or consult with suppliers for specific alloy recommendations.

Prioritize stainless steel if corrosion is your main concern, and factor in lifecycle costs when making your decision.