A Blade-Abrading Method for Surface Pretreatment of Mg Alloys

Sungmo Moon 한국표면공학회 2015 한국표면공학회지 Vol.48 No.5

A blade-abrading method was newly developed for the preparation of clean Mg alloy surface and reported for the first time in detail in this paper. The blade-abrading method includes abrading of the Mg alloy surface with a sharp blade or knife to remove the surface oxide and contaminants on the skin of Mg alloys mechanically, thereby providing very clean surface of Mg alloys. The clean surface prepared by the blade-abrading method in the air was found to be covered with thin and dense air-formed oxide films. Based on the experimental results obtained in this work, it is concluded that the newly developed blade-abrading technique is a very simple and useful pretreatment method which can provide clean and well-defined surface for the following surface treatments.

Quantitative Analysis of the Amount of Aluminium Dissolved in Phosphoric Acid

Sungmo Moon,Cheolnam Yang 한국표면공학회 2017 한국표면공학회지 Vol.50 No.4

The present work addresses how to measure the amount of dissolved aluminum in phosphoric acid, based on volumetric and gravimetric measurements of the precipitates formed by reaction between the H₃PO₄ solution containing dissolved aluminum ions and 10 % KF solution. The volume of the precipitates increased with dilution of the dissolved aluminum-containing H₃PO₄ solution up to 1/4 dilution above which it decreased with further dilution. The lowered amounts of the precipitates at low dilution less than 1/4 and high dilution more than 1/4 are attributed to high acidity of the solution and decreased amount of dissolved aluminum in the solution, respectively. Volumetric measurement of the amount of precipitates was found not to be very reliable with the experiments, while weight measurement of the precipitates after drying for 80 min at 60 ℃ appeared to be very reproducible. In the present work, it is suggested that the amount of Al dissolved in 85 % H₃PO₄ solution can be calculated by multiplying 50 to the weight of precipitate obtained by reacting 8 ml of 1/4 diluted H₃PO₄ solution containing dissolved aluminum ions with 6 ml of 10 % KF solution.

Lateral Growth of PEO Films on Al1050 Alloy in an Alkaline Electrolyte

Sungmo Moon,Yeajin Kim 한국표면공학회 2017 한국표면공학회지 Vol.50 No.1

This article reports for the first time on the lateral growth of PEO (plasma electrolytic oxidation) films on Al1050 alloy by the application of anodic pulse current in an alkaline electrolyte. Generation of microarcs was observed at the edges initially and then moved towards the central region with PEO treatment time. Disc type PEO film islands with about 20 μm diameter were formed first and they grew laterally by the formation of new disc type PEO films at the edge of pre-formed PEO islands. The PEO film islands were found to be interconnected completely and form a continuous PEO film when generation of small size microarcs are terminated at the central part of the specimen, resulting in very smooth surface with low surface roughness less than 1 μm of Ra. Further PEO treatment after the complete interconnection of PEO films islands showed local thickening of PEO films by vertical growth. It is concluded that very mooth PEO film surface can be obtained by lateral growth mechanism rather than vertical growth of them.

PEO Film Formation Behavior of Al1050 Alloy Under Direct Current in an Alkaline Electrolyte

Sungmo Moon,Yeajin Kim 한국표면공학회 2017 한국표면공학회지 Vol.50 No.1

This work demonstrates arc generation and anodic film formation behaviors on Al1050 alloy during PEO (plasma electrolytic oxidation) treatment under a constant direct current in an alkaline electrolyte containing silicate, carbonate and borate ions. Only one big arc more than 2 mm diameter was generated first at the edges and it was moving on the fresh surface or staying occasionally at the edges, resulting in the local burning due to generation of an extremely big orange colored arc at the edges. Central region of the flat surface was not fully covered with PEO films even after sufficiently long treatment time because of the local burning problem. The anodic oxides formed on the flat surface by arcing once were found to consist of a number of small oxide nodules with spherical shape of 3~6 μm size and irregular shapes of about 5 ~10 μm width and 10~20 μm length. The anodic oxide nodules showed uniform thickness of about 3 μm and rounded edges. These experimental results suggest that one big arc observed on the specimen surface under the application of a constant direct current is composed of a number of small micro-arcs less than 20 μm size.

Formation Mechanism of Titanium Dioxide Nanotubes by Anodization

Sungmo Moon,Yongsoo Jeong 한국표면공학회 2008 한국표면공학회 학술발표회 초록집 Vol.2008 No.-

Surface Hardness Measurement of Anodic Oxide Films on AA2024 based an Ink-Impregnation Method

Sungmo Moon,Jong-joo Rha 한국표면공학회 2020 한국표면공학회지 Vol.53 No.2

This paper is concerned with type of imperfections present within the anodic oxide films on AA2024 and surface hardness of the anodic film measured after ink-impregnation. The anodic oxide films were formed for 25 min at 40 mA/cm² and 15±0.5oC and 300 rpm of magnet stirring rate in 20% sulfuric acid solution. The ink-impregnation allows clear observations of not only the imperfections within the anodic oxide films but also an indentation mark on the oxide film surface made by a pyramidal-diamond penetrator for the hardness measurement. There were observed four different regions in the anodic oxide films on AA2024 and the surface hardness of the anodic oxide films appeared to be crucially dependent on the type of defects, showing 60~100 Hv on the oxide surface region I with large size black defect, 100~140 Hv on the oxide surface region II with large size grey defect, 140~170 Hv on the oxide surface region III with mall size black and/or grey defects and 170~190 Hv on the oxide surface region IV without defects. The pyramidal indentation marks were observed to be distorted in the regions with a large size black and grey defects, while no distortion of the indentation mark was observed in the regions with small size defects and without visible defects.

Ink-impregnation method for the study of imperfections and hardness of anodic oxide films on AA2024

Sungmo Moon,Jong-joo Rah 한국표면공학회 2020 한국표면공학회 학술발표회 초록집 Vol.2020 No.6

Surface hardness measurement of NiP-plated AA7050

Sungmo Moon(문성모),Juseok Kim(김주석) 한국표면공학회 2021 한국표면공학회지 Vol.54 No.4

This paper is concerned with the surface hardness measurement of NiP-coated AA7050 using different loads from 10 to 100 g. The surface hardness was observed to increase from 180 to 600 Hv with increasing NiP layer thickness, depending on the load applied for indentation. When NiP coating thickness is thinner than 2 ㎛, the surface hardness of NiP-coated AA7050 was mainly determined by AA7050 substrate, while it was significantly increased by NiP coating layer when NiP coating thickness is thicker than 2 ㎛. Hardness of AA7050 substrate itself was not dependent on the applied load but the hardness of NiP-coated AA7050 was largely influenced by the load applied for indentation. The largest difference of hardness between 10 g and 100g of applied loads, was obtained at the NiP thickness of about 8 ㎛ above which the measured hardness at 10 g reached a maximum value of about 600 Hv. It was also observed that indentation-induced plastic deformation next to the indented zone occurs when NiP layer is 5.64 times thicker than the depth of impression formed by indentation.

Lateral growth of PEO films on Al7050 alloy in 0.1 M NaAlO₂

Sungmo Moon(문성모),Gi Yeob Kim(김기엽) 한국표면공학회 2021 한국표면공학회지 Vol.54 No.4

This paper investigated generation behavior of micro-arcs and growth behavior of PEO films on the AA7050 disc specimen in 0.1 M NaAlO₂ solution under the application of 1200 ㎐ anodic pulse current. Morphologies, thickness and surface roughness of PEO films were examined at the edge part and central part separately. Micro-arcs were generated first at the edge part and then moved towards the central part with PEO treatment time, indicating lateral growth of PEO films. The lateral growth resulted in uniform PEO thickness of about 5 ㎛ and surface roughness of about 0.5 ㎛. Moving of the arcs from the edge towards the central part appeared only one time and large size arcs were generated at the edge before completing the central part with small size micro-arcs. This suggests that vertical growth starts before completing the lateral growth. Large size arcs generated at the edge resulted in the formation of relatively large size pores within the PEO films on the AA7050 disc specimen.

Anodic Surface Finishing Technologies for Metals

Sungmo Moon 한국표면공학회 2019 한국표면공학회 학술발표회 초록집 Vol.2019 No.11