Dezincification of brass?

  • Thread starter gomerpyle
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  • #1
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I have a brass part that is showing signs of corrosion, namely the appearance of dark red spots. Through research I've learned that this is probably caused by dezincification, which can occur after exposure to water, acid, or salt. My question is I have noticed brass corrosion also involves the formulation of copper carbonates from the copper oxidizing (green color). Is this simply a later stage of corrosion after dezincification has taken place, i.e.: once the zinc is selectively leached away then the copper is the only element left to react? So is it a fair assumption to assume dark red sports are simply an early stage of corrosion in brass?

OR, is the greenish color of corrosion the result of a different chemical reaction causing the copper to react and not the zinc? (EX, ammonia attacking brass causing copper to react and not zinc?)
 

Answers and Replies

  • #2
The greenish color is independent of the red rot (dezincification) you see.
 
  • #3
The green coloured corrosion is mostly verdigris . The actual composition of verdigris varies a lot . Usually it is a mixture of several different Copper compounds .

White coloured corrosion sometimes seen is mainly simple zinc compounds .

Dezincification causes the Brass to become porous . Sometimes areas of porosity become active sites for corrosion .

There is always the possibility of electrolytic corrosion when brass is in contact with ferrous metals in wet conditions .
 

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