Abstracts Book - IMRC 2018

• SE4-P007
CORROSION RESISTANT PERFORMANCE OF HYDROXIDE
COMPOSITE FILMS PREPARED ON Mg ALLOYS BY STEAM
COATING
Takahiro Ishizaki 1,2 , Yuta Shimada 3 , Tomohiro Miyashita 3 , Taejun Kim 3 , Ai Serizawa 1
1 Shibaura Institute of Technology, Department of Materials Science and Engineering, Faculty of
Engineering, Japan. 2 Shibaura Institute of Technology, SIT Research Laboratories, Japan.
3 Shibaura Institute of Technology, Graduate School of Materials Science and Engineering,
Japan.
Magnesium alloys have superior physicochemical properties such as high
strength ratio and high damping capacity. 1,2 However, they have a significant
fault that is a low corrosion resistance. Various surface treatment methods have
been developed to improve the corrosion resistance. Chemical conversion have
been frequently utilized, however, they required treatment of liquid waste
before disposal, leading to environmental load. Thus, it is essential to develop
an environmentally-friendly surface treatment method to improve the corrosion
resistance. We have developed a novel and environmentally-friendly coating
technology, i.e., steam coating. 3 In this study, we report corrosion resistance of
films prepared on Mg alloys by steam coating.
Mg alloys with sizes of 20 × 20 × 1.5 mm were used as the substrate. Substrates
were ultrasonically cleaned in absolute ethanol for 10 min. The steam coating
was performed using an autoclave made of stainless steel. 20 mL of ultrapure
water was placed at the bottom of the autoclave to produce steam. The cleaned
Mg alloy was set at substrate stage in the autoclave. The autoclave was
maintained at a temperature of 433 K for 6 h.
XRD patterns of film-coated Mg alloy revealed that the film had some peaks at
approximately 2q = 18°, 33°, 38°, 51°, 58°, 62°, 68°, and 72° which were assigned
to the 001, 100, 101, 102, 110, 111, 200, and 201 diffraction peaks of brucite-type
Mg(OH) 2 . Two peaks at approximately 2q = 11° and 23° could be assigned to 003
and 006 diffraction peaks of Mg 1-x Al x (OH) 2 (CO 3 ) x/2 ·nH 2 O (Mg–Al LDH). These
results show that the crystalline Mg-Al LDH was included in the Mg(OH) 2 film.
Polarization curve measurements demonstrated that the corrosion resistance
of the films coated magnesium alloy was greatly improved compared to the
untreated one. Immersion tests in 5 wt.% NaCl aqueous solution were also
performed to evaluate the corrosion rate of the film coated Mg Alloys.