• Journal of Environmental Health Sciences
• /
• v.36 no.3
• /
• pp.236-246
• /
• 2010

In preparative anti-corrosive coating experiments, polyaniline was obtained by reacting an oxidizing agent with the monomer aniline. Further, the primer coating was prepared using a variety of widely-used materials such as urethane resin. For the top coating, epoxy resin and acrylic urethane resin were used. Characteristics of the coatings were assessed according to KS and ASTM specifications, and the structure of the polyaniline was characterized using FT-IR and TGA. For analysis of anti-corrosive properties in salt-spray experiments, measurements of the oxidation state of iron and surface atomic analysis were conducted using XPS and SEM-EDX. Unlike general anti-corrosive coatings which exhibit anti-corrosive effects only as a primer coating, the anti-corrosive coatings using polyaniline as the anti-corrosive pigment showed a marked synergistic effect with the top coatings. In other words, the top coatings not only produce a fine view effect, but also increase, through interaction with the primer coatings, the resistance to diffusion of corrosive factors from the external environment. It was also found that, unlike the heavy metal oxide-forming layer of the passive barrier alone, the polyaniline anti-corrosive pigment oxidized iron at the interface with the iron substrate to form a passive barrier in the oxidic layer, and itself formed a potential barrier layer with anti-corrosive factors from the external environment. Although the passive layer was damaged, the damaged area did not become completely oxidized iron; on the contrary, it showed a tendency to reduction. This can be interpreted such that a passive layer is formed again on the damaged area, and that at the same time there is a tendency to self-healing.

• Journal of Ocean Engineering and Technology
• /
• v.21 no.3 s.76
• /
• pp.65-70
• /
• 2007

There are many kinds of protection methods for marine structures, with varyingeconomical and environmental advantages. The coating protection method is being widely used in both continental and marine structures. In this study, by adding some additives, such as Zn powder(Zn), carbon black(CB) to epoxy anti-corrosive paint, the effect on the corrosion resistance was investigated throughan electrochemical method. The additive of Zn(20)+CB(10) showed the lowest passivity current density. Polarization resistance in both cyclic voltammogram and impedance measurement of an additive of Zn(20)+CB(10) was also the largest value, compared to other additives. Furthermore, rusting and bubbling was not observed on the surface of the test specimen with the additive of Zn(20)+CB(10), compared to other specimens. It is suggested that the corrosion resistance of the anti-corrosive paint can be improved by using some additives.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.173-176
• /
• 2006

There are many kinds of protection methods for marine structures by using and environmental condition. Coating protection method, one of these methods is being widely adopted to both all ground and marine structures. In this study, by adding some additives such as Zn powder(Zn), carbon black(CB) to epoxy anti-corrosive paint, the effect to promote corrosion resistance was investigated with electrochemical method. Corrosion potentials with additives shifted to negative direction than no additive. However passivity current density increased than no additive except for Zn(20)+CB(10), especially, additive of Zn(20)+CB(10) showed the smallest passivity current density. Polarization resistance of Zn(20)+CB(10) by both cyclic voltammogram and impedance measurement was the largest value than other additives. And also surface phenomenon by adding Zn(20)+CB(10) was observed a good add condition not showing bubbling than other additives.

• Corrosion Science and Technology
• /
• v.12 no.6
• /
• pp.295-303
• /
• 2013

Silane surface treatments have been developed as an alternative for toxic and carcinogenic chromate-based treatments for years. It is consistently observed that ultra-thin films offer excellent corrosion protection as well as paint adhesion to metals. The silane performance is comparable to, or in some cases better than, that of chromate layers. Based on the tetra-ethylorthosilicate(TEOS) and methlyl trieethoxysilane(MTES), inorganic sol was synthesized and formed hybrid networks with $SiO_2$ nano particle and polypropylene glycol(PPG) on Zn alloyed steel surface. According to SST results, addition of 10nm and 50nm $SiO_2$ nanoparticle in synthesized solution improved anti-corrosion property by its shear stress relaxation effect during curing process. Also, SST results were shown that anti-corrosive property was affected by the amounts of organic compounds.

• Corrosion Science and Technology
• /
• v.8 no.3
• /
• pp.126-131
• /
• 2009

The interaction between wear and corrosion can significantly increase total material losses in water chemistry environment. The corrosive wear tests of a PWR steam generator tube material (Alloy 690) against the anti vibration bar material (409 SS) were performed at room temperature. The tests were performed in alkaline water chemistry conditions. NaOH solution was selected for test condition to investigate the corrosive wear effect of steam generator tube material in alkaline pH condition without other factors. The flow induced vibration can caused tube damage and the corrosion can be occurred by water chemistry. The test results showed that, in the alkaline solution at pH 13.9, the corrosion current density was increased about ten times than that in the distilled water. And wear rate at pH 13.9 was increased about ten times from that at neutral condition. However, the wear rate was decreased with time. The decrease would be attributed to the change in roughness of specimen or sub-layer of the worn surface with time. From microstructure observation, severe abrasive shape and several wear debris were found. From those results, it could infer that the oxide film on Alloy 690 changed to easily breakable one in the alkaline water, and then abrasion with corrosion became the main wear mechanism.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.17 no.6
• /
• pp.95-103
• /
• 2013

Half Cell Potential (HPC) technique has been widely adopted for its quantitative evaluation of corrosion possibility. In this study, RC specimens with three different cover depths (10mm, 30mm, and 60mm) and w/c ratios (0.35, 0.55, and 0.70) are prepared and accelerated salt spray test (SST) is performed for 45 days. Steel corrosion occurs in the specimens with 0.55 of w/c and 10mm of cover depth. In the case of 0.70 of w/c and 30mm of cover depth, steel corrosion is also monitored. Considering the effect of cover depth and w/c ratio, HCP evaluation equation is proposed and the condition which can control steel corrosion is obtained. Furthermore, anti-corrosive conditions containing w/c ratio and cover depth are analyzed through Life 365 program and the conditions are compared with the results from this study.

• Journal of the Korean institute of surface engineering
• /
• v.51 no.2
• /
• pp.95-103
• /
• 2018

Recently, many types of constructional steels have been often exposed to under severe corrosive environments due to acid rain with increasing environmental contamination. In order to inhibit their corrosion in severe corrosive environments, a painting method has been widely applied to numerous constructional steels of land as well as marine. Therefore, development of paint having a good quality of corrosion resistance is considered to be very important. In this study, four types of anti-corrosive paints (AP: Phenol epoxy, AC: Ceramic epoxy, AT: Coal tar epoxy, AH: High solid epoxy) were coated to the specimens, and then, were immerged in various salt solutions (0.1, 0.3, 3, 6, 9 and 15% NaCl solutions) for 11 days. And, the corrosion resistance of these samples by effect of osmotic pressure with salt concentration was investigated with electrochemical methods such as measurement of corrosion potential, impedance and corrosion current density. The corrosion current densities of all samples (AC, AT and AH) submerged in 3% NaCl solution exhibited the smallest values compared to other salt solutions. However, in the case of lower values of salt solutions than 3% NaCl solution, the corrosion current density increased again because it makes easier for water, dissolved oxygen and chloride ion etc. to invade toward inner side of coating film due to increasing of the osmotic pressure than 3% NaCl solution, but in the case of higher values of salt solutions than 3% NaCl solution, the coating film is easily deteriorated due to high concentration of chloride ion rather than the osmotic pressure, which resulted in increasing the corrosion current density. In particular, the AC sample indicated the best corrosion resistance in 6% NaCl solution compared to other samples. Consequently, it is considered that the corrosion mechanism of the coated steel plate is completely different from bare steel plate, and the corrosion resistance of coating film by osmotic pressure and chloride ion depend on various types of epoxy of paint in NaCl solution.

• Journal of Advanced Marine Engineering and Technology
• /
• v.22 no.2
• /
• pp.219-224
• /
• 1998

Recently to achieve the anti-corrossive effect in propeller shafts the coating technique with suit-able coating materials is available instead of bronze-sleeved shafts. In this case the coating mate-rials in service must not be delaminated from the shaft and the crack must not be originated. Thus the various performance and security test for coating materials of propeller shaft must be carried out under the real conditions or more severe circumstance. The most important factors effecting on the funtion of coating materials in propeller shaft are the strain and the environment of sea water. In this paper therefore the maximum possible strain which can be occured in real propeller shaft was calculated based on IACA standard classification rule in order to give the proper level of strain to the test samples in performance test of propeller shaft coating materials.

• Journal of Welding and Joining
• /
• v.29 no.5
• /
• pp.58-62
• /
• 2011

Stainless steels are alloy steels with a nominal chromium content of at least 11 percent, with other alloy additions. The stainlessness and corrosion resistance of these alloy steels are attributed to the presence of a passive oxide film on the surface. When exposed to conditions like Resistance Spot Welding (RSW) process that remove the passive oxide film, stainless steels are subject to corrosive attack. And exposure to elevated temperatures causes oxidation (discoloration) of areas around indentation in Spot welding. In this paper, deal with the effect of shielding gas (Ar) preventing the corrosion, oxidation of stainless steel. And find the optimal shielding gas flow rate. In addition, suggest effective purging method for direct/indirect spot welding process.

• Corrosion Science and Technology
• /
• v.15 no.1
• /
• pp.13-17
• /
• 2016

The aim of this study was to evaluate the use of iron-nickel oxide ($Fe_2O_3$.NiO) nanopowder (FeNi) as an anti-corrosion pigment for a different application. The corrosion protection ability and the mechanism involved was determined using aqueous solution of FeNi prepared in a corrosive solution containing 3.5 wt.% NaCl. Anti-corrosion abilities of aqueous solution were determined using electrochemical impedance spectroscopy (EIS) on line pipe steel (API 5L X-80). The protection mechanism involved the adsorption of metallic cations on the steel surface forming a protective film. Analysis of EIS spectra revealed that corrosion inhibition occurred at low concentration, whereas higher concentration of aqueous solution produced induction behavior.