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Corrosion by glycol
Does anyone know, or have any data on glycol's compatibility with tin based brazes. Can glycol attack a joint that has a tin based braze?
thanks
Tino Volpe
Producer of braze - Warwick, Rhode Island, USA
2007
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2007
Pure glycols at ambient temperature may attack tin. The chapter 'Ethylene Glycols' in Materials Selection for the Chemical Process Industries, 2nd Edn., ISBN 1-57698-025-1, mentions "Neither galvanized steel nor tinned steel is permitted in shipment and storage."
The attack on tin is likely less aggressive than that on zinc, as propylene glycol is specified as the adjuvant carrier for corrosion inhibitors used on steel and tinplate per 21 CFR § 178.3300.
Glycols solutions are more corrosive due to DI water, non-DI water, acidity, chloride, copper or other dissimilar metal, heat and oxygen. Heat, light and oxygen degrade glycols into organic acids, and this degradation is accelerated by metals such as aluminum and copper. Hence, pH buffers and corrosion inhibitors are necessary. L. L. Shreir et al., in Corrosion, Vol. 1, 3rd Edn., ISBN 0750610778 (for both vols.) mentions 1% borax, sodium benzoate and 0.1% mercaptobenzothiazole (MBT) as inhibitors for ethylene glycol solutions used in soldered auto radiator systems.
Tin is anodic vs. the Cu6Sn5 & Cu3Sn intermetallics formed by hot dipping tin, soldering or brazing of copper.
See also compatible materials in 'A Guide to Glycols' from the Dow Chemical Co.
http://www.dow.com/PublishedLiterature/dh_02aa/09002f13802aaf25.pdf
The degradation of glycols and the need for corrosion inhibitors is discussed in 'Uninhibited Ethylene Glycol' from Thermo Electron Corp. http://www.thermo.com/eThermo/CMA/PDFs/Various/File_26366.pdf
Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
Ethylene and propylene glycol have been used in billions of auto radiators as antifreeze. Until recently those radiators were brass, soldered together with tin/lead...so...I'm guessing you'll have no problem.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
2007
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Thanks, guys for all that great information. I figured that the auto radiators is basically the same system here but I'm sure that car antifreeze is full of pH buffers and corrosion inhibitors (at least that's what they advertise). Thanks again.
Tino Volpe [returning]
Producer of braze - Warwick, Rhode Island, USA
2007
Sorry! Finishing.com is temporarily Read-Only.
Ted Mooney is retiring but I have several offers to take it over.
We're working hard to make sure we find it the best new home.
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Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.