SEVERE STP corrosion internally on Diesel

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ZMiller
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Re: SEVERE STP corrosion internally on Diesel

Post by ZMiller » Sun Mar 25, 2018 8:58 am

Remembering this is a diesel tank.

Would (any) one guess at what the PH value of this atmospheric condition might be expected to be?

Would (could) one expect a PH of between 6.5 and 9.0?
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Re: SEVERE STP corrosion internally on Diesel

Post by bugbuster » Sun Mar 25, 2018 1:27 pm

Zane:

Were these readouts from permanently installed gauges, or handheld meters?

It makes a difference. In my experience, automated gauges need often need to be cleaned and calibrated more often that manufacturers prescribe.

Assuming that the values are real, it's most likely that they are indicative of minimal circulation (not surprising) and consequent heterogeneity. Folks who venture into the dazzling world of multiple sampling - gauge/meter readings, physical sample collection & sampling - are invariably shocked and dismayed at the variability they discover. In my in press chapter on sampling, in the latest edition of ASTM Manual 1, I spend several pages discussing heterogeneity issues. Remarkably (for me) most of the discussion has nothing to do with fuel/fuel system microbiology.

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Re: SEVERE STP corrosion internally on Diesel

Post by CherokeeUST » Tue Apr 03, 2018 11:06 am

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Re: SEVERE STP corrosion internally on Diesel

Post by bugbuster » Tue Apr 03, 2018 11:30 am

Thanks for this pass along!

It opens with an answer to one of the central questions about ETOH-related corrosion issues: "what's the cost impact?"

Any discussion about investing in preventive measures must begin with a cost-basis. A $1million investment to prevent $80million damage is a bargain. The same investment to prevent an $800,00 problem is not.

I'll comment more, once I've read the full report.

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Re: SEVERE STP corrosion internally on Diesel

Post by CherokeeUST » Wed May 23, 2018 8:11 am

The opinions expressed here are entirely mine and are not endorsed by my employer.

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dieselengine9
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Re: SEVERE STP corrosion internally on Diesel

Post by dieselengine9 » Wed May 23, 2018 8:52 am

Awesome! So all we need to do is come up with a Sulfur additive to treat the diesel tanks :!:

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Re: SEVERE STP corrosion internally on Diesel

Post by bugbuster » Wed May 23, 2018 10:04 am

Great question, Zane.

Of course, pH is a measurement of the hydrogen ion concentration in water. For the non-technical readers of this string, the "p" is shorthand for "negative Log." Google "pH" for more detailed explanation. Theoretically, the pH of tank ceiling condensate water would provide the best surrogate measurement of headspace pH. From a practical perspective, capturing condensate samples is not a trivial task. I ship's tanks, where overhead corrosion, related to fungal growth is an issue, condensate pH values can be <4. I have not seen UST condensate data. That said, remember that aggressiveness (i.e., corrosivity) depends on alkalinity (acidity), hardness, and pH. Alkalinity and acidity are measures of a fluid's resistance to pH change (to measure acidity, one adds caustic to a sample until it reaches a target pH; to measure alkalinity, on adds acid until it reaches a target pH). A hard water, strongly acidic sample at pH 6 can be more aggressive than a soft water, weakly acidic sample at pH 4.

Regarding sulfur: as I've written inprevious posts, thert have now been a number of peer reviewed techincal papers that have demonstrated that biodeterioraiton rates are independent of sulfur concentration in diesel fuels. Yes, some forms of sulfur are toxic (there was a time when surgons dusted wounds with powdered sulfur to prevent sepsis). However, sulfur is one of the basic building blocks of all life. The hydrotreatment process used to desulfurize fuels also beaks aromatic molecules apart. Many aromatics are biocidal (Lysol was orignially orthophynylphenol). Between the reduced aromatic contant and the use of lubricity additives needed to restore fuel lubricity lost due to sulfur and aromatic removal, ULSD is more susceptible than LSD or HSD to biodeterioration.

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Re: SEVERE STP corrosion internally on Diesel

Post by CherokeeUST » Thu Jul 19, 2018 7:11 am

Came across this site today. Some interesting articles.

http://www.materialsperformance.com/
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Re: SEVERE STP corrosion internally on Diesel

Post by bugbuster » Thu Jul 19, 2018 1:56 pm

Right! MP is NACE's version of PEI Journal. If you search the archive (I'm not sure if non-NACE members can), you'll find tons of great articles addressing all aspects of corrosion, including my personal favorite - MIC

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