**1. Is there corrosion between 304 and 316?**
Generally, no. Since both 304 and 316 are austenitic stainless steels with similar electrochemical potentials, they can typically be used together without significant galvanic corrosion. The risk of corrosion is very low in most normal environments, such as atmospheric or freshwater conditions. However, in highly conductive electrolytes like saltwater or certain chemical solutions, there is a theoretical risk, though it remains very small due to their similar nobility.
**2. What is the main difference between 304 and 316?**
The main difference is the addition of molybdenum. Type 316 stainless steel contains 2-3% molybdenum, while Type 304 has none. This molybdenum significantly enhances 316's resistance to corrosion, particularly against chlorides and other industrial solvents. This makes 316 much better suited for harsh environments, such as coastal areas or chemical processing applications.
**3. Is 316L stainless steel good quality?**
Yes, 316L is considered a very high-quality and versatile stainless steel. The "L" stands for "Low carbon," which gives it excellent resistance to sensitization (grain boundary carbide precipitation) and intergranular corrosion, especially after welding. This combination of very good corrosion resistance (thanks to its molybdenum content) and superior weldability makes 316L a premium-grade material for demanding applications in marine, chemical, pharmaceutical, and architectural fields.
**4. What are common problems with 304 steel?**
The most common problems with 304 stainless steel are:
* **Pitting and Crevice Corrosion:** It is susceptible to attack from chlorides, which can be found in saltwater, de-icing salts, and some industrial chemicals. This can lead to localized pitting.
* **Stress Corrosion Cracking (SCC):** Under tensile stress and in the presence of chlorides and high temperatures, 304 can be prone to cracking.
* **Sensitization:** When heated in the range of 800-1500°F (425-815°C), carbon in 304 can precipitate with chromium at grain boundaries, reducing chromium content nearby and making the material susceptible to intergranular corrosion. This is a key concern for welding thicker sections.
**5. What is the temperature difference between 304 and 316 stainless steel?**
Both grades have similar high-temperature strength and scaling resistance in intermittent service up to about 1600°F (870°C). However, 316 generally performs better in continuous high-temperature service, especially in environments containing sulfurous gases or chlorides. The molybdenum in 316 provides better resistance to creep and scaling at elevated temperatures (above approximately 800°F / 427°C) compared to 304, giving it a slight advantage for certain high-temperature applications.
