Vulcan Materials cem20u ml-138078 ユーザーズマニュアル

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Corrosion on metals is everywhere. It is
recognized quickly on iron and steel as
unsightly yellow/orange rust. Such metals are
called “active” because they actively corrode
in a natural environment when their atoms
combine with oxygen to form rust.

Stainless steels are passive metals because
they contain other metals, like chromium,
nickel and manganese that stabilize the atoms.
400 series stainless steels are called ferritic,
contain chromium, and are magnetic; 300
series stainless steels are called austenitic,
contain chromium and nickel; and 200 series
stainless, also austenitic, contains
manganese, nitrogen and carbon. Austenitic
types of stainless are not magnetic, and
generally provide greater resistance to
corrosion than ferritic types.

With 12-30 percent chromium, an invisible
passive film covers the steel’s surface acting as
a shield against corrosion. As long as the film is
intact and not broken or contaminated, the metal
is passive and stainless. If the passive film of
stainless steel has been broken, equipment
starts to corrode. At its end, it rusts.

There are three basic things which can break
down stainless steel’s passivity layer and
allow corrosion to occur.

1. Mechanical abrasion
2. Deposits and water
3. Chlorides

Mechanical abrasion means those things that
will scratch a steel surface.  Steel pads, wire
brushes and scrapers are prime examples.

Water comes out of the faucet in varying degrees
of hardness. Depending on what part of the
country you live in, you may have hard or soft
water. Hard water may leave spots, and when
heated leave deposits behind that if left to sit, will
break down the passive layer and rust stainless

steel. Other deposits from food preparation and
service must be properly removed.

Chlorides are found nearly everywhere. They
are in water, food and table salt. One of the
worst chloride perpetrators can come from
household and industrial cleaners.

Here are a few steps that can help prevent
stainless steel rust.

When cleaning stainless steel products,
use non-abrasive tools. Soft cloths and
plastic scouring pads will not harm steel’s
passive layer. Stainless steel pads also
can be used, but the scrubbing motion
must be in the direction of the
manufacturer’s polishing marks.

Some stainless steel comes with visible
polishing lines or “grain.” When visible
lines are present, always scrub in a motion
parallel to the lines. When the grain cannot
be seen, play it safe and use a soft cloth or
plastic scouring pad.

While many traditional cleaners are loaded
with chlorides, the industry is providing an
ever-increasing choice of non-chloride
cleaners. If you are not sure of chloride
content in the cleaner used, contact your
cleaner supplier. If your present cleaner
contains chlorides, ask your supplier if
they have an alternative. Avoid cleaners
containing quaternary salts; it also can
attack stainless steel and cause pitting
and rusting.

Though this is not always practical,
softening hard water can do much to
reduce deposits. There are certain filters
that can be installed to remove distasteful
and corrosive elements. To insure proper
water treatment, call a treatment specialist.