Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Citric Acid

Galvanic Corrosion of Dental Alloys and Amalgam in Artificial Saliva Containing Citric Acid

Rana A. Majed

Engineering and Technology Journal, 2013, Volume 31, Issue 12, Pages 2200-2310

In this work galvanic corrosion potentials and currents were measured using
polarization curves of some dental alloys (amalgam, Co-Cr-Mo, Ni-Cr-Mo, SS 316L, Ti-
6Al-4V alloys) in artificial saliva containing citric acid with three concentrations 3,6 and
9 g/l at 37oC. All galvanic corrosion data were measured to coupling of amalgam and
other alloys to investigate the galvanic corrosion between filling and other dental devices
such as partial-denture framework, crowns, bridges, and endodontic instruments.
The results of galvanic corrosion show that the coupling between amalgam and Ni-
Cr-Mo alloy gives higher galvanic corrosion current than other metallic contact, and then
the contact between amalgam and Co-Cr-Mo alloy was heavier compared with coupling
of SS 316L and Ti-6Al-4V alloy with amalgam. The increasing of corrosion for alloys
containing chromium due to rapidly converting of Cr6+ to Cr3+ and this phenomenon
decreases the concentration of chromium ions at surface and then increases the
dissolution of metal atoms, while decreasing of galvanic corrosion of Ti-alloy coupled
with amalgam due to the passive oxide surface layer (TiO2).

Using Citric Acid As An Admixture and It's Influence on Some Properties of Concrete

Wasan I. Khalil

Engineering and Technology Journal, 2009, Volume 27, Issue 1, Pages 32-41

The objective of this investigation is to find the effectiveness of the citric acid as
retarding admixture. The experimental results indicate that the optimum dosage of citric
acid is 0.02% by weight of cement. This dosage causes a delay in initial and final setting
time of 1:42 and 3:18 hour: minute, respectively; and a reduction in water-cement ratio
of 13% relative to reference concrete mix. So, citric acid can be classified according to
ASTM-C494 as water-reducing and retarding chemical admixture type D.
The investigation also extends to evaluate the effect of using citric acid on
properties of concrete such as, compressive strength, splitting tensile strength, modulus
of rupture and dynamic modulus of elasticity at normal conditions and after exposure to
salt solutions. Generally the results indicate that using citric acid in concrete enhance it's
properties at normal conditions, the percentage increase in compressive strength,
splitting tensile strength, modulus of rupture and dynamic modulus of elasticity at age
180 days was about 56%, 13%, 24% and 8% respectively relative to reference concrete.
Also it was observed that concrete containing citric acid has good performance after 180
days exposure to salt solution in comparison with reference concrete.