Corrosion problem on tin plated brass buttons

Dear all,

Now we have corrosion problem on button material brass with tin plating. During sampling (100 pieces) with 1% NaCl, 24 hr, 38 °C the result is PASS (no discoloration). I also try 3% NaCl, 6 hr, 40 °C, the result still PASS (no discoloration). But our customer complaint that the buttons (material brass with tin plating) change color to dark brown within 4 days during transportation. Do you have any suggestion about this? Can humidity faster corrosion condition (now rainy season in my country) only less than 1 week? Is there any way to check corrosion condition ?

My guess is that the copper is migrating up thru a thin tin coating. Consider a nickel strike under the tin.

Thanks for your information. After we check plating condition, the corrosion button was not our products.

Corrosion product have plating step as below :

Material Brass + Copper Strike + Nickel Plating

Our Product have plating step as below :

Material Brass + Nickel color plating (Nickel-free and lead-free: alloy of tin etc)


After we check corrosion plating condition, nickel plating too thin. Then Copper easy to migrate become discoloration.