For carbon dioxide- Stainless steels are fit for use

For Chlorides- Duplex stainless steels are recommended

For H2S- Nickel based alloys are suitable

Heanjia Super-metals is offering the wide series of corrosion resistance alloys in the best of its class that meet the variable strength needs of your applications. For support in choosing the best fit alloy, contact us online or make a call at +86-134-2641-5867. 

Carbon dioxide and general corrosion

Carbon dioxide (CO2) is the wide source of general corrosion in oil and gas processing plants. In availability of water, carbon dioxide produces carbonic acid that is extremely corrosive in nature. Water condensation usually occurs in the gas areas if the temperature decreases below to dew point. This may specifically become an issue in initializing or shutting down the plant. Besides of water and CO2 magnitude, the attack rates are based on temperature, pH, flow rate and availability of oxygen or organic acids. Acidification and finishing fluids may also make the corrosive agents severe.

The best fact of corrosion resistant alloys is to provide the protection from corrosion by the presence of chromium which develops a security layer. The usefulness of this scale is based on the concentration of chromium. In the nominal conditions the martensitic stainless steels comprise of 13% chromium that is sufficient although if pH lowers down to 3.5, the use of austenitic-ferritic duplex stainless steels is preferred. The chromium steels containing 13% Cr content must not be employed for water injection wells without observing the pH for present and future well environments.

Chloride, oxygen and pitting attack

Chlorides or oxygen may affect the security level of chromium oxide layer causing pitting or crevice attack. Such type of corrosion occurs catastrophically that is complicated to determine. Moreover, the magnitude of chloride and oxygen describes that pitting attack is based on temperature, pH and speed values. For chloride magnitude above 1,000 ppm or oxygen magnitude above 10 ppb, you must use the alloys with large PREN number. Here the martensite stainless steels cannot offer the adequate security. To avoid localized attack in marine water or in high oxygen contamination conditions, PREN of alloy must be above 40.

Chlorides in availability of large tensile stress conditions can cause stress corrosion cracking at the high temperatures. Here the use of high nickel alloys is recommend that are resistant to stress corrosion cracking. Alloys with larger nickel magnitude above 42% such as Nickel span C902 that is resistant to SCC from chlorides.

Hydrogen Sulfide, hydrogen and environmental caused cracking

H2S or hydrogen sulphide in availability of tensile stress may cause catastrophic damage due to hydrogen embrittlement by means of sulphide stress cracking and stress corrosion cracking. Hydrogen embrittlement is caused by other sources such as cathodic security that is normally used in marine water. These damages are usually delayed however occur rapidly without visible warning and may occur at stresses lower than the yield strength. The factors causing environmental assisted cracking are partial pressure of Hydrogen sulphide and carbon dioxide, temperature, pH, chloride and stress.

Conditions with partial pressure of hydrogen sulphide more than 0.05 psi are found sour and cracking can simply be prevented by specific selection of materials. The significant increase in hydrogen sulphide over the service life of the oil well should be taken into consideration. Here Inconel 718 serves the industrial needs of gas units for sour conditions.

The material characteristics enhancing the environmental assisted cracking resistance includes composition, microstructure, processing history and toughness. The martensitic stainless steels may be sufficient where the partial pressure of H2S is below to 1.5 psi and pH is more than 3.5, 25Cr Super Duplex stainless steel is suitable for 3 psi H2S. The nickel base alloys are recommended for use that are used without the limitation to H2S content, besides of their large PREN to prevent pitting corrosion.

 Virtually many traditional copper alloys and pure copper is sensitive to stress corrosion cracking. The alloys that can withstand such corrosion are cupronickel 90/10 and cupronickel 70/30.

The conditions that cause SCC in aqueous ammonia are water, ammonia air or oxygen and tensile stress in the metal. Fracturing is usually intergranular that needs only trace magnitudes of ammonia in several cases and takes place at ambient temperatures.

The thermal stress reduction is not just a better kind of preventive measure because ammoniacal stress corrosion cracking takes place at minor stresses. Normally mild ammonia based conditions like cooling tower water units employ copper-nickel alloy 90/10 that offers adequate performance. Minor magnitudes of hydrogen sulphide are found to prevent SCC of brasses in petroleum refinery treatment streams definitely by decreasing the magnitude of dissolved oxygen magnitude.

There are nickel based alloys that are also prone to SCC in the different conditions. Although stabilized alloys Incoloy 825 and Inconel 625 are inhibitors to this type of attack. They are suggested for use in the petrochemical process streams where chlorides are present with polythionic acids.

It is found that Nickel 200 and Nickel 201 are resistant to many conditions. Monel 400 is resistant in annealed and thermally stress-relieved conditions. Atmospheric air or oxygen speeds up the corrosion rates and SCC susceptibility. But Monel 400 offers excellent resistance to general corrosion over a large range of temperature and concentration limits hence its use in HF alkylation systems and other operation streams comprising of HF or fluorides is extensive. Thermal stress relief at the lowest temperature of 540oC or 1000of will inhibit SCC attack and offer long service life.

Design of petrochemical system consideration

Several corrosion damages occur due to bad design of system or equipments, inadequate fabrication of piping and units and improper precautions to be used to decrease the atmospheric failure. It is possible to control the corrosion or decrease it by good design that is achieved by taking the surface conditions, surface smoothness, cleanliness, dissimilar material control, prevention of crevices, suitable design of supporters, by offering suitable drainage, preventing electrical contact among the unlike metals, preventing sharp edges in the pipes, offering thicker structures to be careful of the impingement, considering the standards, adequate structure withstanding vibration and choosing plant position unwind from the different polluting sectors, by preventing vapour spaces, non-uniform and stress dispersions from metal surface temperature, atmosphere, stress, by welding process, preventing the contaminants, decreasing fluid speed, maintenance and replacement of failed components etc help in improving the outcomes. An adequate welding process choice is also crucial. Construction material and corrosion allowances must be chosen on the base of expected attack or material failure rates in the aggressive combination of process parameters and prolong material performance of similar kinds of services and operations and facilities.

Internal pipe corrosion

However dry crude oil and gases with standard additives are non-attacking in nature, they can become vigorous when contact with water and air. Carbonate or biocarbonate have been found as responsible for stress corrosion cracking of internal pipe lines. 

External pipeline corrosion

A pipeline while in service is open to several types of corrosion. The attack on the material surface in contact with soil occurs by direct soil attack includes the presence of corrosion cells on the pipe surface or dispersed current attack in which stray driven electricity causes attack on the pipe in contact with soil.

Corrosion prevention

Choosing the correct corrosion resisting material for construction, using corrosion inhibitor, avoiding the contact of material with attacking media, changing the media by process alteration, choosing electrochemical control methods such as cathodic and anodic security, producing and fabricating the material to decrease the localized attack and corrosion analysis.

Avoiding material contact with the corrosive media

In addition of choosing the suitable construction alloy material, in many cases surface treatments for example coating, heat processing, diffusion processing and surface finishing are also significant in controlling the corrosion of the material in the specific corrosive media. Coatings can be done with metallic or ceramics. In addition of external coating, internal coating of pipelines, storage containers and other are also demanded. For use in petrochemical plants and refineries, securing the heated surfaces from breaching, boilers, heat exchangers, stills, furnaces and several other equipments need the higher levels of coating. Coating is the premiere line of security from the corrosion. It offers several characteristics such as direct application, efficient adhesion to pipe surface, chemical and electrical stability and versatility.

Why Us for Petrochemical alloys?

Heanjia Super-Metals is the trusted supply for Oil and Gas and petrochemical products. We not just keep the stock that you demand in fact we are also specialized in value added services. The oil, gas and petrochemical sectors need special materials for their processes. Many operations can easily leave the machines unworkable and lost deliveries, for which you need to an industrial expert who can supply the extensive product knowledge and provide the chain management to offer the materials delivered on time as guaranteed. We are a leading manufacturer and metal specialist for use in the oil and gas and petrochemical processing systems.

Reasons for choosing us as your best resource

1. Heat processing, cutting length and grinding value added services.
2. Rapid turn-around on value added services
3. Skilled, professional and trained supportive team
4. Vast stock and supply
5. Competitive cost
6. Heat lot traceability
7. Long bar stock offers additional length flexibility
8. Large capacity bars
9. Cutting tolerances

Corrosion and erosion are the main wear mechanisms that occur in the chemical and petrochemical industries. Stainless steel, nickel alloys and nickel based alloys are widely used in the oil and petroleum refining industries for offering excellent corrosion resistance in aqueous, gaseous and high temperature conditions for their good mechanical characteristics at the entire range of temperatures from cryogenic to the high limits and are prominent for their special physical features. Nickel plating is employed for its corrosion prevention and toughness. Moreover, the nickel based alloys are used as catalysts.

Heanjia Super-Metals is a leading Chinese manufacturer and processor of corrosion resistant and high performance alloys for use in the petrochemical and refineries market.

Our materials include high temperature and corrosion resistant materials that offer remarkable performance in the construction and processing plants of refineries. Becoming the leading global supplier of high performance precision fabricated products, our sales team is backed by technical marketing team and in-house production and testing facility enables Heanjia to consistently fulfil and exceed your requirements. We offer a complete range of solutions to meet the needs of demanding operations that include bar, sheet, coil, pipe, tube, flanges, wire and strips, laser cut components and machines parts are ideal for an extensive range of challenging applications.

We stock Hastelloy B-2, B3, C-276, Monel 400, Inconel 600, 601, 625, Incoloy 800H/HT, Stainless steel 310S and 321 and duplex steel grades 2205 and 2507.

Common applications

Pressure vessels, heat exchangers, condensers, separators, fractional distillation towers, crude heaters, hydro heaters, transfer lines, drums, flare tips, protection systems, flow control system etc.

By following the demands of this tempting industry, we always strive to use the innovative technologies to meet your stringent needs. We offer a special line of high performance materials that offer excellent corrosion resistance and high processability.

The established alloys for petrochemical processing industry are 800H, 600, 601, 617, 625 that contain the major elements such as chromium, nickel and minor magnitudes of molybdenum, titanium, cesium, nitrogen and columbium (or niobium).

Chromium and molybdenum enhance resistance to localized corrosion whilst with nitrogen they improve the inhibition to chloride stress corrosion cracking. Availability of nitrogen increases localized corrosion resistance. Increasing the magnitudes of chromium and molybdenum increase the resistance of stainless steels against pitting and crevice corrosion. Stainless steel with high molybdenum content has offered good resistance to chloride induced corrosion cracking in aqueous sodium chloride. Sulphide stress corrosion is a key issue in the petroleum and petrochemical industry because of availability of hydrogen sulphide. Large strength alloys such as nickel based alloys are less resistant to sulphide induced stress corrosion cracking when mixed with iron showing that the damages are caused by hydrogen charging the metal while the corrosion.

Choosing the suitable material to control the corrosion attack in the crude oil processing systems such as for construction, crude desalting with water, neutralizing the crude and vacuum column overhead, water rinsing in crude column overhead system and using the corrosion preventer. Resistance of alloys to concentrated sulfuric acid increases with improving the magnitude of Chromium (Cr), Molybdenum (Mo), Copper (Cu) and silicon (Si). Attack of sulfuric acid is widely based on concentration, temperature limit and acid speed. High Ni-Cr-Mo alloys for example Hastelloy C-276, Hastelloy C-22 etc can suitably handle the sulfuric acid at all magnitudes. Nickel, chromium, molybdenum, copper and silicon are the major elements to improve the corrosion resistance characteristics of alloys in the units handling sulfuric acid.

High temperature halide resistance increases by improving the magnitudes of nickel and chromium. Decreasing molybdenum and tungsten improves the resistance of an alloy to oxidizing halogen attack. Titanium offers ideal resistance to sulphur dioxide, hydrogen sulphide and nitrogen and general operations in refineries including regenerators, boilers and overhead condensers. In the commercial scale elevated temperature process conducted at 750oC, the commonly employed materials are Chromium-Molybdenum steels.