6 Alloys With Aqueous Corrosion Resistance

Aqueous corrosion resistance; the key to better sleep for every marine engineer!

If you’re looking for an alloy with outstanding resistance to aqueous corrosion, the below six are some of the best alloys on the market.

All alloys listed have incredible resistance to various forms of aqueous corrosion, including acids such as Sulfuric, Hydrofluoric, Nitric, Hydrochloric, salts, and seawater.

INCONEL® Alloy 22

Alloy 22, also known as Nickel alloy 22 or Hastelloy C-22, this high-grade alloy offers a wide variety of corrosion resistance. Its aqueous corrosion resistance is known as a top choice for resistance at higher temperatures. This alloy is used frequently for processing nuclear fuel and, thanks to its resistance to seawater, general marine industries.

INCONEL® Alloy 625

This nickel-chromium alloy offers high strength and thermal strength, resistance to oxidation and resistance in a large range of temperatures. This INCONEL alloy is known for its versatility which makes it a great choice for within a number of industries. It is known for its incredible heat-resistance, up to 815°C cryogenic temperatures. Inconel 625 has proven indispensable within the aerospace and marine industries.

INCONEL® Alloy 625LCF

This version of 625(LCF – Low Cycle Fatigue) is specifically designed with low cycle fatigue resistance at temperatures up to 649°C. Apart from the LCF benefits, this alloy holds properties similar to alloy 625 because of such a closely related chemical composition.

INCONEL® Alloy 686

Used mostly in areas of extreme corrosion – classed as a “super alloy”, Inconel 686 provides function at high temperatures and stresses. With a content of 59% Nickel, 19-23% Chromium and up to 17% Molybdenum on average, it can handle up to 104700 psi (tensile strength.)

INCONEL® Alloy G-3

Alloy G-3 is a nickel-chromium-iron alloy that has good weldability and resistances to intergranular corrosion. It is commonly used for dealing with phosphoric and sulfuric acids in particular. Another alloy developed by Special Metals Corporation, it has a low carbon content and high resistance to atmospheric and acid corrosion. It is machinable with use of high-speed tools at a continuous pace to avoid work-hardening.

INCOLOY® Alloy 825

Alloy 825, (along with Inconel 625) is one of the most popular choices of alloy for resisting corrosive substances. Most Incoloy’s in the 800 series, such as 800, 800H and 800HT are known for their incredible heat resistance, especially in treatment plants, pipelines, and tubing. Incoloy 825 is just as impressive, giving fantastic overall resistances, with high strength and resistance against stress-cracking, pitting and intergranular corrosion.

We recommend 825 for customers requiring a material that lives up to the “super alloy” name, particularly within petrochemical, oil and gas, pollution and processing industries.

Waverley Brownall manufacture fittings, components and valves from INCONEL® and INCOLOY® Special Metals materials for engineers within the UK and around the world.

The corrosion of metals is the destructive attack of an alloy and its material properties by an external environment.

With roughly 71% of the Earth’s surface being water, it’s not surprising that aqueous corrosion is such a big concern.

If left to corrode, metal (as part of large structures such as those in the offshore industry) can cause devastating damage.

4 Types Of Aqueous Corrosion

Galvanic Corrosion

This is the most basic form of aqueous corrosion. It occurs when two metals have physical or electrical contact with each other and are immersed in a (liquid) common electrolyte. A car battery is a common example of galvanic corrosion at work, the natural process of corrosion is used to supply electrical energy.

Filiform Corrosion

Filiform is actually a type of Galvanic corrosion that can often be seen on painted alloy engine components working in harsh industrial environments. The thread-like corrosion can appear on coated metals such as steel, iron and even zinc.

Continue scrolling for prevention tips.

Pitting Corrosion

Pitting is one of the most commonly known types of corrosion that can happen to a range of alloys. It is a gradual breakdown of the metals surface. In this type of corrosion, it tends to penetrate the metal rather than spread and this is particularly notable on horizontal surfaces where gravity affects the intensity of the pitting.

Crevice Corrosion

As the name suggests, this type of corrosion is seen commonly in areas where metals are overlapping or areas of cracking. This occurs when one part of a metal is exposed to a different oxygen concentration than other parts. It is not a corrosion type that is exclusive to stainless steels – it can also effect other alloys such as aluminium and copper.

How can Aqueous Corrosion be prevented?

1. One way in which many industries are working against corrosion is to cover their alloys in a resistance coating.

“Rising demand for high performance anti-corrosion coatings in oil & gas, marine, power generation, construction, and other industries is estimated to positively impact the market growth by 2023.”

Source: High performance anti-corrosion coatings, High demand from emerging economies boosts market, industry outlook 2016 to 2023 by Transparency Market Research and Your Oil and Gas News

2. The use of special metals on instrumentation, valves, fittings and pipeline can help prevent the effects of corrosion. High performance alloys that counter aqueous corrosion are especially useful for industries such as Offshore, to be used on rigs and piping applications.

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Waverley Brownall are proud to supply numerous companies where seawater is one of the biggest issues facing the performance of an alloy. Our engineers understand the severity of corrosion issues and work towards providing the best solutions to prevent costly – and potentially, life-threatening problems.

Corrosion

Learn more about the selection of special metals for corrosive environments.
Covering atmospheric and acidic demands.