SEM: Investigation of corrosion in plant engineering and construction

In technical procedures damages due to corrosive processes occur frequently. The illustration of the damage symptoms and of the involved phases, mostly microscopic scale, can be realized by electron microscopy. In the present case an Al-pipe was examined which showed corrosive symptoms (pitting) as well as formation of new substances in form of white mineral efflorescence.

Other than that macroscopic image, small, brown, radial aggregates were found at the inner surface of the pipe. The base of this formation traces an intact inside of the pipe and contains predominantly Ca and S. These elements were deposited from the medium flowing through the pipe. Subsequently the wall started to dissolve and due to the formation of Al oxides the actual corrosive process took place. The increase in volume of the new substances and crack formation continually led to the solution of the Al-pipe and finally to partial pitting.