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Carbon steel cantilever beams are widely used in many applications
in aerospace, civil and mechanical engineering. Pitting corrosion is a
phenomenon which places severe limitations on the design of such applications.
As such, understanding this phenomenon and the methods to deal with it, are of
a great importance. This paper presents numerical investigation by using F. E.
(Finite Element) simulation on the load carrying capacity of corroded
cantilever beams with pitting corrosion damage. The pitting corrosion hole
shape has been modeled using ASTM G46 Standard Guide. Several different cases
of pitting corrosion, represented by hemispherical holes, were modeled and
examined by using ANSYS computer program. Clamped edge constraint was used on
one end, while the other end was free. In these F. E. models, element
of Solid95 was used and comparison to Bernoulli-Euler theory was made. The
effect of the radius of the pitting corrosion holes on the stresses in the beam
was examined in comparison to yield stress. It has been found that the M. S.
(Margin of Safety) has been reduced gradually with increasing radii. Agreement
with Bernoulli-Euler theory has been achieved only for small radii. Moreover,
three methods of pitting corrosion repairs were examined, together with Bernoulli-Euler
theory comparison: 1) Regular surface repair; 2) Extension
surface repair; and 3) “Handy Removal”. It was found that extension surface repair
has the highest M. S. value.
The corrosion inhibition efficiency (IE) of an aqueous extract Allium cepa (onion) in controlling the corrosion of carbon steel ground water in absence and presence of with Zn2+ has been studied by weight loss method. The formulation consisting of 3 mL Allium cepa extract, 50 ppm of Zn2+ and 50 ppm of sodium pattassium tartarate which offers 97% inhibition efficiency. The synergistic effect exists between onion-Zn2+-tartarate system. The addition of N-cetyl-N,N,N- trimethylammonium bromide on onion-Zn2+-tartarate system does not change the excellent inhibition efficiency. Polarization study shows that the onion-Zn2+-tartarate system functions as a cathodic inhibitor. AC impedance spectra reveals that a protective film is formed on the metal surface. The UV fluorescent spectra indicate the possibility of formation of Fe2+-onion complex and also Zn2+-onion complex in solution. Thus the protective film is found to be UV fluorescent.