On Jun 28, 10:12 pm, "Michael Koblic" wrote:
I am going to run a small trial of various surface coatings to assess their
ability to protect steel from corrosion (rusting). A bunch of identical
steel washers, coated on one side with the experimental substance and
uncoated on the other side as a control will be suspended in salty water for
a period of time.

It occurred to me that brine may not be the best simulation of corrosion
occurring naturally. Can anyone suggest anything else?

--
Michael Koblic,
Campbell River, BC

Salt will make otherwise acceptable treatments fail. Cor-ten is the
steel that is left unpainted.
http://greenisles.com/objectio.htm

I ran this test by surface-grinding steel scrap to get a clean oil-
free surface, applying patches of several spray-on preservatives, then
leaving it out under the gutter downspout. The roof concentrates at
least some of the pollution in the air so I think that was an
intensified but accurate test of rust in this area. The result was
that LPS-3 lasted the longest, around 6 months, and I bought a few
gallons. In less severe places it lasts 2-3 years for me, about as
advertised. There are still a few unrusted spots on the bare machined
steel of my front end loader, which has been outside (covered) for 4
years and used on snow that contains road salt. I use the other,
cleaner sprays on my basement machines and tools.

If you have a lot to protect the pump spray bottle and bulk refills
are much cheaper than spray cans and you can dilute the thick product
with kerosine so it wicks into threads and cracks and rust pits
better. I bought what the local MSC store had in stock; you might find
something better where you are.

We ran a similar test in a materials science course in college. Strips
of steel were left immersed in tap water, sodium hydroxide, and zinc
chromate solutions. The water rusted its strip in a day, the lye in 2
weeks, the chromated strip stayed shiny all semester.

Military rifles were oxidized to iron oxide or phosphate and oiled.
They are a very severe application because they have precision bearing
surfaces that are exposed to salt water, rain and sand and a failure
is fatal. The Springfield Armory test was to leave prototypes on the
roof for a few weeks. The climate here is often very humid, currently
91%. In a drier climate phosphate + oil protects for a very long time.
The oil was butter, not mentioned in this article:
http://en.wikipedia.org/wiki/Iron_pillar_of_Delhi

Supposedly the best protection for steel is an etching primer and
automotive paint. I repainted the rusty bumpers on my truck that way
about 10 years ago and haven't seen any rust. More recently I tried
brush-on zinc paint on the bed fenders; the top coat didn't adhere
well and some rust shows.

There are several anti-corrosion greases available for moving wear
surfaces that you can't paint. LPS-3 dries to a thick wax rather than
a good grease. LPS used to sell LPS-100 which was a better lube but I
haven't seen it in years. I have enough and haven't tested the others.
http://www.lpslabs.com/product_pg/co...Corrosion.html

I like the spray-can chain lube for motorcycles and garden equipment.
The industrial stuff with graphite or moly is effective but hard to
wash off clothing. Lubriplate marine trailer bearing grease works
pretty well, too.

Jim Wilkins