cleanser stain on cylinder liners

[neo3]

I removed the heads on an LS engine, prior to having them worked on. This means of course I had to do a lot of cleanup work on the block surfaces before the heads can be re-installed (which won't happen for awhile). I found that Barkeepers Friend cleanser, which contains oxalic acid and also some citric acid, works great to remove the gasket remains that can't be scraped off the aluminum block. But some drips ran down the cylinder bores (which are iron liners), and after wiping them away, they left stains in the metal, which are sort of just more silvery/white than the surrounding area, which is more brownish/yellowish. I've tried cleaning the stains away with acetone, and wd40, but no effect. The honing lines are not affected as far as I can tell, and the surface still feels completely smooth. So there must have been some chemical interaction. Could this be related to ingredients in the oil that was run (PP 5W30 Euro L)? I do use Lubegard Biotech, which has lots of moly and Phosphorus, could that actually coat the metal in a way that acetone can't remove it, but the oxalic acid did? Has anyone seen that kind of staining before?

 

[Dave9]

Yes acid can discolor metal. It has nothing to do with the oil, is a reaction between the acid and the metal. I wouldn't worry about (not that slight, mild amount) it as long as it is still completely smooth.

However if it is more silvery/white and the rest is more brownish/yellowish, it seems more like it cleaned the area it contacted rather than stained it, at least initially until it ate through to the metal, then just left a cosmetic blemish.

Had you tried using a plastic scraper or a gentle hand with a razor blade?

 

[CT8]

Gasket remover?

 

[sdowney717]

Metal is porous. The oxalic acid has bleached the oil stains which is embedded in the metal. Dont worry about it.