Mag Drive 5 with metal screws

A question - I ordered a Mag Drive 5 pump; it arrived today, and when I
unpacked it I saw it has metal screws holding the impeller housing. Is
that normal? It states salt water application, but I'm not comfortable
with metal for salt and would appreciate your opinions. (I contacted
Danner and am waiting for a reply, but I'd like your input as well.)

Thanks!
Marty

MartyPowerJazz wrote:
A question - I ordered a Mag Drive 5 pump; it arrived today, and when I
unpacked it I saw it has metal screws holding the impeller housing.

Hi Marty,

Many people replace the metal screws with nylon ones. Here's a link
with some info on sizing (the message is almost at the bottom of the
page):
http://tinyurl.com/yexo45

Depending on where you live, you may be able to find them locally but,
if not, US Plastics has them for about US$0.03 each:
http://tinyurl.com/ycjaeo


Corrosively yours,

Alex

They are safe.

Wayne Sallee
Wayne's Pets



MartyPowerJazz wrote on 11/2/2006 10:22 PM:
A question - I ordered a Mag Drive 5 pump; it arrived today, and when I
unpacked it I saw it has metal screws holding the impeller housing. Is
that normal? It states salt water application, but I'm not comfortable
with metal for salt and would appreciate your opinions. (I contacted
Danner and am waiting for a reply, but I'd like your input as well.)

Thanks!
Marty

Alex and Wayne,

Thanks! I had a few minutes from work to give Danner a call - they told
me that the screw are medical grade stainless steel, so as Wayne said,
they're safe. I'm going to avoid my usual overdoing and try not to
order the plastic ones...

Marty

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

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

Mag drive uses two types of screws, stainless steal, and a
dark colored screw. The dark colored screw holds up better
than the ss screw. It seems odd the way they sometimes use
one over the other.

Wayne Sallee
Wayne's Pets

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

Tidepool Geek wrote:

The article describes why stainless steel is stainless and also why
stainless steel often isn't stainless in certain environments.

It also describes the some of the different formulae for stainless steels. One
thing it doesn't make clear is the fact that each of the different types of
stainless is susceptible to different types of corrosion and immune to others.
The type which is called "CRS" by the USN is relatively benign in a marine
environment. Other types may pit badly or otherwise corrode.

George Patterson
If there are obstacles, the shortest path between two points may be the
crooked one.