Corrosion-resistant alloy

Japanese: 耐食合金 - たいしょくごうきん（英語表記）corrosion-resistant alloy

An alloy material that can withstand use in a corrosive environment. The criteria for determining whether an alloy is corrosion-resistant or not are often as follows: an erosion rate of 0.05 mm/year or less is completely corrosion-resistant, 0.05-1.00 mm/year is corrosion-resistant, and 1.00 mm/year or more is not corrosion-resistant. Alloys that fall into the category of completely corrosion-resistant or corrosion-resistant are called corrosion-resistant alloys. Corrosion-resistant alloys include iron alloys, nickel alloys, copper alloys, aluminum alloys, and titanium alloys.

[Katsuhisa Sugimoto]

Iron alloy

Iron-chromium and iron-chromium-nickel alloys containing 12% or more chromium are called stainless steels, and are the most widely used of all corrosion-resistant alloys. Other low-alloy corrosion-resistant steels include weathering steel, which has high resistance to atmospheric corrosion, seawater-resistant steel, which has excellent corrosion resistance in seawater splash zones, and dew-point corrosion-resistant steel, which is resistant to sulfuric acid dew-point corrosion caused by sulfur in combustion gas. Additionally, acid-resistant cast irons such as Durilon, which contains 15% silicon, and Niresist, which contains 15-30% nickel, are also used.

[Katsuhisa Sugimoto]

Nickel Alloys

They are characterized by their high corrosion resistance in reducing acids and alkalis, and their resistance to chloride stress corrosion cracking. Well-known examples include Monel, a nickel-copper alloy, Inconel, a nickel-chromium-iron alloy, and Hastelloy, a nickel-molybdenum alloy.

[Katsuhisa Sugimoto]

Copper alloy

It has excellent corrosion resistance against the atmosphere and natural water, and is also characterized by its resistance to flowing seawater. Well-known alloys include aluminum brass, which is a copper-zinc-aluminum alloy, cupronickel, which is a copper-nickel alloy, tin bronze, which is a copper-tin alloy, and aluminum bronze, which is a copper-aluminum alloy.

[Katsuhisa Sugimoto]

Aluminum alloy

It has good corrosion resistance in neutral aqueous solutions, but poor resistance to acids and alkalis. Aluminum-magnesium alloys and aluminum-manganese alloys are known as corrosion-resistant alloys, and these have good corrosion resistance even in seawater.

[Katsuhisa Sugimoto]

Titanium Alloy

Pure titanium has good resistance to many acids and chlorides, but there are also titanium-molybdenum alloys with improved corrosion resistance to reducing acids, titanium-palladium alloys with improved self-passivation properties, and titanium-tantalum alloys with improved corrosion resistance in high-temperature, high-concentration nitric acid.

[Katsuhisa Sugimoto]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

腐食環境中での使用に耐える合金材料。耐食合金であるか否かの判定のための規準としては、侵食度が0.05ミリメートル／年以下のものを完全耐食、0.05～1.00ミリメートル／年のものを耐食性あり、1.00ミリメートル／年以上のものを耐食性なしとすることが多く、完全耐食または耐食性ありの部類に入るものが耐食合金とよばれている。耐食合金としては鉄合金、ニッケル合金、銅合金、アルミニウム合金、チタン合金などがある。

［杉本克久］

鉄合金

クロムを12％以上含む鉄‐クロムおよび鉄‐クロム‐ニッケル合金はステンレス鋼とよばれ、耐食合金のなかでもっとも使用量が多い。そのほか、低合金耐食鋼として大気腐食抵抗性の大きい耐候性鋼、海水飛沫(ひまつ)帯で優れた耐食性を示す耐海水鋼、燃焼ガス中の硫黄(いおう)に起因する硫酸露点腐食に強い耐露点腐食鋼などがある。また、耐酸鋳鉄として、ケイ素を15％含むデュリロン、ニッケルを15～30％含むニレジストなども使われている。

［杉本克久］