Abstracts Book - IMRC 2018

• SE2-P028
SIMULTANEOUS IMPROVEMENT OF CORROSION RESISTANCE
AND STRENGTH OF Al-Mg-Si ALLOY BY STEAM PROCESS
Ai Serizawa 1 , Kotaro Mori 1 , Yuta Shimada 1 , Takahiro Ishizaki 1
1 Shibaura Institute of Technology, Materials Science and Engineering, Japan.
Al alloys have been used as advanced structural materials in automobile, railway
and aerospace industries because of the excellent physical and mechanical
properties such as low density, and high specific strength and ductility. Their low
corrosion resistance, however, hinders their use in the corrosive environment.
To improve the corrosion resistance of the Al alloys, the development of a novel
coating technology has been highly desirable. In this presentation, we report a
newly-developed process, “steam process”, which enables to control the
corrosion resistance and strength of Al alloy simultaneously using only steam.
In this study, Al-Mg-Si alloy and Al-Zn-Mg alloy were used as a substrate. The
substrates were ultrasonically cleaned in absolute ethanol for 10 min. The
cleaned substrates were set in the autoclave. Ultrapure water was located at the
bottom of the autoclave to produce steam. The autoclave was heated to a
temperature of 373 to 453 K, and then held at this temperature for up to 48 h,
and was subsequently cooled naturally to room temperature, resulting in the
formation of anticorrosive films on magnesium alloys. The resultant films were
characterized by XRD, XPS, FE-SEM and electrochemical measurements. FE-SEM
image of film surface treated at 453 K for 48 h using steam demonstrated that
plate-like nanostructure was densely formed on the surface. XRD patterns
indicated that the film formed on two types of Al alloys by steam process was
mainly composed of crystal AlOOH. The Micro-Vickers hardness of the Al alloys
was increased by applying the steam process. The potentiodynamic polarization
curves of the film coated and uncoated substrates after immersion in the 5 wt%
NaCl aqueous solution for 30 min revealed that the corrosion current density,
j corr , of the film coated substrates decreased by more than two orders of
magnitude as compared to the uncoated substrates, indicating that the
corrosion resistance of the alloys alloy were improved by the formation of the
film via steam process.
Acknowledgment:
This research was supported by Japan Science and Technology Agency (JST)
under Industry-Academia Collaborative R&D Program Heterogeneous Structure