Mag Drive 5 with metal screws

rust WILL hurt stuff. SPS will start to die with rust in the system, The
screws on the mag pumps will eventually rust in salt water. Save yourself
the headache and the money and replace them with nylon screws from us
plastics

"Wayne Sallee" wrote in message
k.net...
Rust won't hurt anything. Rust is iron oxide. There are other metals in
stainless steel, but I would not think that they would stay in solution
any longer than iron.

As far as stainless steal holding up in salt water, that depends on the
grade of stainless steal.

Low oxygen does not cause rust. In fact keep iron in an oxygen free
environment, and it will never rust.

But yes the chlorine in the salt can dissolve it by creating metal
chlorides. I would not worry about it unless it was creating a structural
problem.

Where screws corrode fast is where they are in contact with a different
metal in salt water.

Wayne Sallee
Wayne's Pets



Tidepool Geek wrote on 11/3/2006 2:26 PM:
MartyPowerJazz wrote:
I'm going to avoid my usual overdoing and try not to
order the plastic ones...

Hello again,

Before you decide that replacing the screws is "overdoing" read this:
http://tinyurl.com/y9jqz7

The article describes why stainless steel is stainless and also why
stainless steel often isn't stainless in certain environments.
Specifically, two situations that can overcome the chemistry of SS are
as follows:

1. An oxygen poor environment - This is what you get on SS surfaces
that are in tight contact with another surface such as in the case of
SS screws. It's sometimes referred to as "crevice corrosion" and is a
well known problem in the marine trades (ships, boats, offshore oil
rigs, etc.)

2. Galvanic corrosion - This one comes from the chloride ions in
sal****er attacking the protective film that SS produces on its
surface; basically, seawater is capable of breaking down this film
faster than the SS can regenerate it.

Read through the thread I linked in my earlier post and you'll see that
some of the participants had rusting of the SS screws in their Mag 5's.
One guy claimed that it caused some mortality in his tank but I'm a bit
suspicious of that claim. OTOH: At the very least, corroded screws
would make pump maintenance more difficult.

Caveat: I have never owned a Mag 5 but I have seen many instances of
crevice corrosion in sal****er environments.


Stainlessly yours,

Alex