Galvanic Corrosion of Brass Tubesheet 1

[eml]

We have a brass exchanger tubesheet with Monel tubes. The brass tubesheet is failing in a manner that I haven't seen before. The brass is coming off in a "stringy" type fashion instead of pitting or cracking. Is this common in brass ? Is this typical of brass/monel galvanic corrosion ?

 

[mcguire]

brass with more than 15% zinc and without tin undergo dezicification. The less corrosion resistant zinc is lost leaving a porous network of copper. see the Metals Handbook, desk edition page 7.36 for explanation and solutions.