Useful Testing

New thread started at the member's request.

There has been no end of concern about scratching the surface and leaving something to promote growth. 1000 different opinions, 1000 different quotes, 1000 different solutions. Limitless headbutting and personality conflicts but nobody has taken the time to prove it. I think that's what we really need. This is the first step in a series of tests I'm going to run that should put all of this to an end. The next will be a process specific corrosion test on various passivation methods versus surface conditions. For the time being, let's start with the whole scratching the surface issue.

I'm not intending to step on anybody's toes or compare size of genitalia. I am interested in useful testing with comparative results in a real world environment that is specific to a homebrewer's perspective.

I started with a top of an AB beer keg and attacked it with various abrasive surface treatments.

Photo #1 The Keg Top
Photo #2 A used 40gt flapwheel in a 4-1/2in grinder
Photo #3 Used 100gt sandpaper in a random orbit sander
Photo #4 The standard Scotch Green Scrubbie

Photo #5 Scotch S/S Scrubbie
Photo #6 A S/S Toothbrush
Photo #7 Polished on a bench buffer.

Surface analysis showed:
The untreated surface of the keg interior was 24ra
The 40gt Flapwheel was 80-115 ra (depending on the location of the test)
The 100gt sandpaper was 16ra
The Green Scrubbie was 18ra
The S/S Scrubbie was 27ra
The S/S Toothbrush was 19ra
The polished area was 10ra or less.

So, just about any scrubbing short of a grinder will provide a surface near original or even better.
(Keeping in mind that this data is based on a beer keg kettle. If you have a pretty Blinkmann polished brewpot the starting surface ra is probably closer to 10ra and and scrubbing short of polishing will likely be a step down.)

Stay tuned.... The next test will be various forms of surface passivation and process specific corrosion testing on varied surface treatments. Anything particular that you guys might want to address in the next test?