Which statement about stainless steel is true?

• A. Stainless steel corrodes rapidly in rain.
• B. Stainless steel will stain other metals when in contact.
• C. Stainless steel is magnetic in all grades.
• D. Stainless steel resists corrosion and will not stain other metals when in contact with them.

Answer: (D)

Stainless steel resists corrosion because a chromium-rich passive film forms on its surface, protecting the metal from rust in many environments, including rain. That’s why the claim that it corrodes rapidly in rain isn’t correct. When stainless steel is in contact with other metals in the presence of an electrolyte, galvanic action can occur, causing the less noble metal to corrode more quickly; however, the stainless steel itself remains protected and does not typically transfer staining to the other metal. In practice, stainless steel will not stain or leave marks on nearby metals under ordinary conditions. Also, magnetism varies by grade, so saying it’s magnetic in all grades isn’t true. The statement that best fits is that stainless steel resists corrosion and will not stain other metals when in contact with them.