Hello,


You state that because there are visible ‘‘Black Patches’’, the tank may be in need of draining.


The ideas that we must consider are:

The ‘‘Black Patches’’ will be removed by draining,

and

If not removed, the ‘‘Black Patches’’ inside of the tank may cause problems.


To consider the factual content of the above statements we must understand what exactly are ‘‘Black Patches’’ and how they could be affected by draining. We must also consider the origins of the ‘‘Black Patches’’.

Consider the following document:

https://www.autosteel.org/AM/Template.cfm?Section=Home&TEMPLATE=/CM/ContentDisplay.cfm&CONTENTID=32139

The steel fuel tank samples were exposed to different fuels and examined at the end of a test regimen. In the Terne (Lead-Tin) coated steel fuel tank, ‘‘Black Patches’’ were observed. Microscopic examination of the ‘‘Black Patches’’ revealed an oxidation of the Terne coating with no damage to the base steel metal. Because metal oxides often form in crystalline structures, the viability of draining the ‘‘Black Patches’’ away is highly questionable. This was also the note of the author, as there was no contamination of the fuel stock.


Therefore, if we only consider the above evidence, the ‘‘Black Patches’’ are benign and cannot be removed by draining.


Goatman