Hastelloy G30 (UNS N06030) is a nickel-chromium-iron alloy. Developed by Haynes International, this alloy offers a unique combination of resistance to both oxidizing and reducing acids.
This article provides a comprehensive overview of Hastelloy G30 plate properties and their uses.
Hastelloy G30 Plate Key Properties
1. Exceptional Resistance to Wet-Process Phosphoric Acid
Hastelloy G30 demonstrates proven resistance to wet-process phosphoric acid, having been used successfully in evaporator tubes for over 30 years.
Wet-process phosphoric acid (P₂O₅) is produced by reacting phosphate rock with sulfuric acid. This industrial process creates a highly corrosive environment containing impurities such as unreacted sulfuric acid, metallic ions, fluoride ions, and chloride ions. The acid must be concentrated through evaporation, typically from about 30% to 54% P₂O₅ concentration, using metallic tubing that must withstand continuous corrosion.
G30 alloy excels in this environment due to its high chromium content combined with molybdenum and copper additions. Laboratory tests conducted at 121°C in actual wet-process phosphoric acid from Florida producers have confirmed the alloy's superior performance. The iso-corrosion diagrams developed by Haynes International show that G30 maintains corrosion rates below 0.1 mm/year across a broad range of acid concentrations and temperatures, significantly outperforming standard stainless steels like 316L and even many competing nickel alloys.
2. Superior Resistance to Oxidizing Acids
The high chromium content of G30 provides outstanding resistance to oxidizing acids such as nitric acid and mixtures containing nitric acid.
With approximately 30% chromium-one of the highest levels among nickel-based alloys-G30 forms a stable, protective oxide layer on its surface when exposed to oxidizing environments. This passive film effectively shields the underlying metal from attack by nitric acid, sulfuric acid, and complex mixtures such as nitric-hydrochloric and nitric-hydrofluoric acid combinations.
Testing data shows that G30 maintains corrosion rates below 0.1 mm/year in sulfuric acid concentrations up to 50% at temperatures approaching 80°C. In nitric acid environments, the alloy demonstrates even greater resistance, making it suitable for metal pickling operations and chemical processing equipment where oxidizing conditions prevail.
3. Moderate Resistance to Reducing Acids
Through its molybdenum and copper content, G30 possesses meaningful resistance to reducing acids such as hydrochloric and sulfuric acids.
While G30 is not primarily designed for pure reducing environments-where alloys like Hastelloy B-series excel-it offers a balanced performance that proves valuable in complex industrial processes where acid conditions fluctuate between oxidizing and reducing states. The alloy contains approximately 5.5% molybdenum and 2% copper, both of which enhance resistance to hydrochloric acid and sulfuric acid in reducing conditions.
Corrosion testing reveals that G30 maintains corrosion rates below 0.1 mm/year in hydrochloric acid concentrations up to 2.5% at 150°F and up to 1% at boiling temperatures. In sulfuric acid, the alloy performs well at concentrations up to 30% at moderate temperatures, with corrosion rates below 0.1 mm/year in 40% sulfuric acid at 125°F (52°C).
4. Resistance to Chloride-Induced Stress Corrosion Cracking
Unlike standard austenitic stainless steels, Hastelloy G30 offers significant resistance to chloride-induced stress corrosion cracking.
Chloride stress corrosion cracking (Cl-SCC) is a common failure mechanism in 304 and 316 stainless steels when exposed to chloride-containing environments under tensile stress. This phenomenon can lead to sudden, catastrophic failure without significant prior corrosion.
G30's nickel-rich matrix (approximately 43% nickel) provides inherent resistance to this failure mode. Combined with its high chromium content and molybdenum additions, the alloy maintains structural integrity even in environments containing chlorides-a critical advantage in evaporators, heat exchangers, and piping systems where chloride concentration can occur beneath deposits or during concentration processes.
5. Resistance to Grain Boundary Precipitation
G30 exhibits excellent resistance to the formation of grain boundary precipitates in the heat-affected zone, allowing use in the as-welded condition without post-weld heat treatment.
Many corrosion-resistant alloys suffer from sensitization during welding-the precipitation of chromium carbides at grain boundaries that depletes chromium and creates pathways for intergranular corrosion. G30 overcomes this limitation through careful control of carbon content and the addition of niobium, which preferentially forms stable carbides.
This characteristic makes G30 particularly valuable for large fabrications where post-weld heat treatment would be impractical or cost-prohibitive. Welded components can be placed directly into service without the risk of intergranular attack, significantly reducing manufacturing time and costs for chemical processing equipment.
6. Excellent Fabricability and Weldability
Hastelloy G30 can be readily formed by conventional methods and welded using standard techniques with matching filler metals.
The alloy exhibits good cold forming characteristics due to its high ductility. However, it is stiffer than austenitic stainless steels, requiring more energy during forming operations. Hot forming is typically performed at temperatures between 950°C and 1150°C, followed by rapid cooling to maintain corrosion resistance.
For welding, ERNiCrMo-11 filler metal is recommended, and processes such as TIG, MIG, and shielded metal arc welding are suitable. The welding area must be kept clean to avoid contamination by sulfur, lead, or other impurities that could compromise corrosion resistance. The standard solution heat treatment consists of heating to 1177°C (2150°F) followed by rapid air cooling or water quenching.
Hastelloy G30 Plate Primary Applications
1. Phosphoric Acid Production Equipment
G30 plates are widely used in evaporator tubes, piping, and vessels for wet-process phosphoric acid concentration, where the alloy's corrosion resistance has been field-proven for decades.
The concentration of wet-process phosphoric acid is one of the most demanding applications in the chemical industry. Evaporators operate at elevated temperatures and handle acid containing chlorides, fluorides, and solid particles. G30's combination of resistance to general corrosion, localized attack, and stress corrosion cracking makes it the preferred material for this service.
2. Nuclear Fuel Reprocessing and Waste Management
The alloy's resistance to nitric acid-based solutions makes it suitable for nuclear fuel reprocessing facilities and radioactive waste treatment systems.
In the nuclear industry, G30 components are used where materials must withstand highly oxidizing conditions combined with radiation exposure. The alloy's stability in nitric-hydrofluoric acid mixtures-common in fuel dissolution processes-makes it a reliable choice for critical equipment.
3. Metal Pickling Equipment
G30 plates are employed in nitric acid-based pickling operations for stainless steel and other metals.
Pickling tanks and associated equipment must resist a combination of nitric and hydrofluoric acids at elevated temperatures. G30's excellent resistance to these oxidizing acid mixtures ensures a long service life in these demanding applications.
4. Petrochemical Processing and Fertilizer Manufacturing
The alloy serves in equipment for the production of pesticides, fertilizers, and petrochemicals where mixed-acid environments are encountered.
G30's balanced corrosion resistance makes it suitable for handling sulfuric acid, nitric acid, and complex mixtures in chemical processing plants. Applications include reactors, heat exchangers, piping, and agitation equipment.
5. Gold Ore Extraction
G30 is used in gold processing facilities where nitric and sulfuric acids are employed for ore treatment.
The gold mining industry utilizes G30 in equipment that handles acid solutions for gold extraction processes, benefiting from the alloy's combination of corrosion resistance and good mechanical properties.
6. Flue Gas Desulfurization Systems
For environmental control equipment, G30 plates provide resistance to the acidic condensates and chloride-containing environments in flue gas desulfurization systems.
In coal-fired power plants and industrial facilities with acid gas scrubbing systems, G30 offers reliable performance against sulfuric acid condensates and chloride-induced corrosion, often outperforming stainless steel alternatives.
Contact our sales team for detailed specifications, competitive pricing, or expert advice for your application.
