Which materials are compatible with methanol

[mrmalcolm]

Methanol is corrosive to certain materials, however, opinions vary on which materials are compatible with methanol.

For example,
(1) can aluminum alloys, bronze, copper alloy, cast iron, nickel steel, galvanized steel, lead alloys, etc. be applied to methanol fuel systems(methanol tank, methanol piping, pumps, valves, vents and their joints).
(2)Can methanol pipelines be connected using flanges
Your promote reply will be greatly appreciated.

 

[3DDave]

Nothing personal but the Methanol.org people do:

https://www.methanol.org/wp-content...of-Metals-Alloys-in-Neat-Methanol-Service.pdf

 

[shvet]

(2)Can methanol pipelines be connected using flanges

Methanol is a serious public health concern. In some jurisdictions fittings are restricted or even prohinited to avoid MeOH stealing and infiltration to food grade EtOH market.
Here are some notable examples of mass MeOH poisoning incidents:
2019 Costa Rica: 25 dead
2016 Russia: 78 dead after ingesting body lotion
2012 Cambodia: 49 dead and over 300 hospitalized after drinking rice wine
2012 Czech Republic: 28 dead and 4 in Poland
2001 Estonia: Pärnu, 68 dead and 43 disabled after the consumption of bootleg liquor
2000 El Salvador: ~122 dead from consuming low-quality liquors

 

[mrmalcolm]

Thanks very much for your early reply.

According to the document "Compatibility-of-Metals-Alloys-in-Neat-Methanol-Service", corrosion rates of cast iron Valves(ductile cast Iron ASTM A 395 heat treated), for applications in methanol service are very-very low: 0.02 in/year.However, the literature did not mention the purity of methanol.It has also been reported in another literature, cast iron are prone to general corrosion, sometimes pitting corrosion. Considering the diversity of methanol fuels((It's likely to contain contaminants in it), are cast iron valves unsuitable for methanol fuel service?

 

[3DDave]

Neat-Methanol is 99.85% pure.

 

[mrmalcolm]

Thank you for your professional reply. According to the above description, if it is neat-Methanol, corrosion rates of cast iron for applications in neat-methanol service are very-very low. For applications in other types of methanol, cast iron are prone to general corrosion, sometimes pitting corrosion.Is the above understanding correct?Thanks al lot.

 

[shvet]

B.3 Corrosivity to metals, alloys, gaskets, and plastic
Corrosivity points immediately to the issue of materials selection, which in turn points directly to application. What type of equipment is in question: pumps, piping, vessels, heat exchangers distillation towers, accumulators, reformer furnaces, strippers, etc.? What are the normal, abnormal, and emergency process conditions? What are maximum, minimum, and typical control parameters: flow, temperature, pressure, composition, impurities, etc.? Is it a batch process or a continuous process? What is the anticipated inspection and testing schedule, the anticipated maintenance program, the intended service life? Given a particular selection, what are the anticipated failure modes and mechanisms?
All of these considerations enter into materials selection. The process is technically complex and organizationally difficult. The vast array of conditions and circumstances that fall within the purview of materials selection for methanol service means that the most appropriate material is based on the particular details of the specific application. While issues pertaining to materials selection are fundamental and likely among the most often asked questions, there are no standard or universal answers. Recognizing this, the following guidance is provided as very general in nature. It is the responsibility of those asking the questions to search out the best answers for their particular circumstance.
• Pure anhydrous methanol is mildly corrosive to lead and aluminum alloys and more so to magnesium, and platinum. That is not to say that aluminum alloys are unfit for methanol service, but rather to alert users to the necessity of periodic inspection and nondestructive testing. Positive materials identification, inspection, and nondestructive testing are essential for fitness for continued service. This applies to all pressure boundary materials in all chemical services, including methanol. Rate of attack on aluminum alloys is typically a slow pitting form of corrosion; however, it can be accelerated to the point of compromising integrity of structural components if not anticipated and monitored.
• Methanol-water solutions can be corrosive to some non-ferrous alloys depending on application and environmental circumstances. This caution applies to equipment built with copper alloy, galvanized steel, titanium, aluminum alloy components, and some plastics and composites. Coatings of copper (and copper alloys), zinc (including galvanized steel), and aluminum exhibit corrosive degradation of various types and at various rates depending on circumstances accompanying application. In general, corrosive attack of structural components such as aluminum alloy floating roofs on storage tanks is slow; it requires periodic visual inspection and nondestructive testing to verify “fitness for continued service.” The same can be said for heat exchanger tube materials, pump components, valve trim, and sensing elements in direct contact with methanol.
• Mild steel is usually selected as the construction material, provided moisture is excluded from the system. If moisture and trace amounts of inorganic salts are expected to exist within the system from time to time, then one should consider upgrading from carbon steel to 316 L stainless steel or a titanium or molybdenum stabilized grade of 316 L stainless steel. The issue in the presence of moisture and inorganic salts is corrosion within weldheat-affected zones. Weld integrity can become an issue.
• Best practice uses molybdenum-stabilized low carbon 300 series stainless steel. Though expensive, this material protects against generalized corrosion, pitting corrosion, stress corrosion cracking, hydrogen induced cracking, and product contamination. Mild steel is widely used for piping. Piping connections are made with welded flanges and methanol compatible gaskets. Threaded connections are not considered suitable in methanol service. Non-ferrous materials should not be used for the construction of permanent pipework. It is recommended that underground storage, buried pipelines, and underground piping be protected with a cathodic protection system and be inspected on a regular basis.
• Many resins, nylons, and rubbers, such as neoprene, nitrile (Buna-N), and ethylene propylene (EPDM), are suitable, though some are more suitable in flowing applications than others. Buna-N is NOT recommended by its manufacturers for dynamic applications (i.e., service in flowing methanol). Buna-N is satisfactory for fluid-static applications; however, it is not considered to be a superior material for methanol service.
• Fluorinated materials such as Teflon are used satisfactorily as equipment components in methanol service. Of these, Teflon offers good dimensional stability and is resistant to attack and degradation.
• Rubber hoses should have an internal wire coil for strength and electrical continuity. Use of hoses should be restricted to temporary applications, such as loading and unloading. Hose material must be compatible with methanol service. All hoses should be clearly labeled for methanol service only. Hose ends must be capped or otherwise protected to avoid contamination during storage. Hoses should be periodically replaced with new hoses, rather than kept in service to the point of failure.
• First-time hose and piping must be washed with water and then methanol to ensure that contaminants are removed before being placed in service.
...
Methanol is one of the few specialized environments that may cause stress corrosion cracking (SCC) in titanium alloys. SCC failures have occurred in dry methanol, methanol/acid, and methanol/halide mixtures.

https://www.methanol.org/safe-handling/

 

[MortenA]

i think your problems will be with any elastomers. Check this first.

BUT you could have tried good ol' google, this was at the very top (for metals and alloys):

https://www.methanol.org/wp-content...of-Metals-Alloys-in-Neat-Methanol-Service.pdf

and this was the second (for elastomers):

https://www.methanol.org/wp-content...ty-of-Elastomers-in-Neat-Methanol-Service.pdf

so it seems like there should be some common cheap alternatives to select from

Best regards, Morten



--- Best regards, Morten Andersen