Prise winners list

Development of steel plate (Eco Coat®-S) for biofuel tank, drastically improving the corrosion resistance

Tobata-ward, Kitakyushu-City
Nippon Steel Corporation, Yawata Steel Works
Other award winners
Teruaki Isaki, Yusho Koyama, Yasuhito Goto, Yuji Sueki, Seiji Sugiyama, Yasuo Takahashi, Masahiro Nunoda, Toshinori Mizuguchi, Shinichi Yamaguchi
Recommended by
The Japan Steel and Iron Federation

Kurosaki, Masao  (50)
Technology Development Dept., Yawata Technical Research Div.
Zinc Plating Research Group
Chief Researcher

The surface of steel plate, not the plating bath, must be controlled to solve the problem. This new idea led to establishment of a breakthrough technology

If biodiesel fuel is stored for a long period, a part of it changes to formic or acetic acid, and bioethanol fuel easily contains water. Therefore if biofuel is kept in a usual metal tank, it may oxidize. This company developed a technology for precise control of the fine plate tissues in submicron order and stable manufacturing of the wide range of products in the same productivity as conventional one. It also developed and commercialized the highly corrosive-resistant tin-zinc plated steel plate for biofuel tanks.


Zinc could not be dispersed uniformly. Everything we performed for control of the plating bath bore no fruit.

People rely on the biofuel on as a carbon-neutral fuel because it is made of grains that grow by absorbing CO2. 
However, the biofuel has one disadvantage for practical use. If the biodiesel fuel is left in a fuel tank for a long period, the plant oil contained in it turns to acid. The bioethanol fuel also tends to contain water because it is water-soluble. In Japan, a plan for mixing a certain amount of biofuel with the gasoline and light oil is ongoing, but if corrosive fuel is contained in a conventional tank, it may oxidize.
"Conventionally lead or aluminum plating was used, but the lead is easily affected by acid and the aluminum reacts to alcohol. We needed new plating that could withstand these two substances.
This company started development of new plaiting in 2000 and Mr. Kurosaki joined in its team two years later. They were trying to further advance the tin-zinc plating (Eco Coat®-T) that were already commercialized together with the aluminum plating because a combination of tin and zinc had a prominent property. Tin has very high corrosion resistance but if it is damaged and the base iron is exposed, it oxidizes. Although it is very unlikely that the interior of the tank is damaged, its exterior may be hit by a stone or exposed to salt contained in an antifreezing agent strewn on a road when it snows and may oxidize. 
However, even if zinc plate is damaged, zinc melts and protects the base iron and this property of zinc is called "sacrifice corrosion prevention".
"Tin has a good barrier effect and zinc has a sacrifice corrosion prevention, and so if these two are combined, it is an ideal combination. However, when the tin-zinc plating was performed in the conventional method, the intended effect could not be obtained. The zinc was segregated (distributed unevenly and solidified) and was not dispersed evenly.
A section, on which zinc is deposited thickly, oxidized selectively and the corrosion resistance of the base steel plate deteriorated.
In tin-zinc hot-dip plating, a steel plate is dipped into a bath of the plating metal that is melted at high temperature and after it is pulled up, gas is blown to the surface to uniform the attached plate amount and it is cooled to solidify the plate. In this process, zinc gathers at a certain section and is solidified.
"We changed the cooling speed, added coagulant into the plating bath and repeated our experiments. However, no new measures for the plating bath produced good results. Then we found a fact"
When we solidified the melted plate, we blew gas to its surface. Therefore we thought that the surface that was exposed to the gas cooled first, but this was not the case. The steel plate cooled first.

Textural control in submicron order solved the problem

"We thought that if we treated the surface of steel plate to accelerate solidification, the problem would be solved because solidification nucleus was formed on the steel plate surface."
We treated the steel plate surface specially before plating to make it finely irregular and performed plating. Then the zinc was distributed evenly. It took Mr. Kurosaki six months to achieve this. However he had to study harder to solve another problem.
"We had to find the conditions in which zinc was distributed evenly, and it was very important for us to establish a manufacturing method to have the same quality regardless of difference in on-site operation."
There was no shortcut to find the optimal conditions. We only had to change the conditions and repeat our experiments. Finally we developed a technology for very fine textural control to have about 10 billion pieces of 0.1m (micron meter) depth of irregularity per 1cm2. We conducted an accelerated corrosion test by exposing the subject plate to salt water equivalent to actual running of ten years, conducted corrosion tests using deteriorated fuels and had to spent three years to establish a stable manufacturing technology. Finally we commercialized the new generation tin-zinc plated steel plate "Eco Coat –S" in July 2005. 
Biofuel is not used widely in Japan. However, "Eco Coat®-S" is used for the fuel tanks of nearly half of new cars that are sold in Japan because it can be used for both biodiesel and bioethanol fuels and its material can be recycled 100%. Technology for using biofuel for automobiles is developing behind the scenes. This company is supporting that development.

Nippon Steel Corporation, Yawata Steel Works

Apr. 1950
419.5 billion yen (for entire Nippon Steel Corporation)
17,646 (for entire Nippon Steel Corporation as of March 2009)
Brief information:
Established as Governmental Yawata Iron & Steel Works in1901. This leading company in the steel industry manufactures the automobile steel plates, railway rails, etc.

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This simulator is used to conduct hot-dip plating in the laboratory. The melted metal (tin and zinc in the case of Eco Coat®-S) is poured into the center bath and a steel plate is submerged into the bath from the upper part to plate it.


This fuel circulating corrosion tester tests the interior of a fuel tank. Corrosive fuels such as deteriorated gasoline containing water are poured into the tank and circulated to conduct an accelerated corrosion test.


The pretreated steel plate is tin-zinc plated to manufacturer Eco Coat®-S. One coil is 2000 to 3000m long, and manufacturers produce fuel tanks from this coil.