Page 287 - untitled

Parker Hannifin Corporation
Parflex Division
Ravenna, Ohio
281
Coiled Air Hose,
Fittings
& Accessories
Hydraulic &PneumaticHose & Fit.
PTFEHose &Fittings
The
rmoplasticTu
bing
Truck (Fleet)
Products
Tooling &Equipment
Hose
Accessories
Technical &
Design
Information
Approvals &
Guides
Alphanumeric
Index
Metals Corrosion Scale
Corrosion of Base Metals in Contact
Electromotive or Galvanic Series for Metals
Magnesium
Magnesium alloys
Zinc (Parker steel fittings are zinc plated)
Berillium
Aluminum 5052, 3004, 3003, 1100, 6053
Cadmium
Aluminum 2117, 2017, 2024
Mild steel (1018), wrought iron, free machining steel (12L14)
Low alloy high strength steel, cast iron
Chrome iron (active)
430 Stainless (active)
302, 303, 321, 347, 410, 416, stainless steel (active)
Ni-resist
316, 317 stainless steel (active)
Carpenter 20Cb-3 stainless (active)
Aluminum bronze (CA 687)
Hastelloy C (active) Inconnel 625 (active) Titanium (active)
Lead/Tin solder
Lead
Tin
Inconnel 600 (active)
Nickel (active)
60 Ni-15 Cr (active)
80 Ni-20 Cr (active)
Hastelloy B (active)
Naval brass (CA 464), Yellow brass (CA 268), Brass (CA360)
Red brass (CA 230), Admiralty brass (CA 443)
Copper (CA 102)
Maganese bronze (CA 675), Tin bronze (CA 903, 905)
410, 416 Stainless (passive) Phosphor bronze (CA 521, 524)
Silicon bronze (CA 651, 655)
Nickel silver (CA 732, 735, 745, 752, 754, 757, 764, 770, 794)
Cupro Ni 90-10
Cupro Ni 80-20
430 Stainless steel (passive)
Cupro Ni 70-30
Nickel aluminum bronze (CA 630, 632)
Monel 400, K500
Silver solder
Nickel (passive)
60 Ni 15 Cr (passive)
Inconnel 600 (passive)
80 Ni 20 Cr (passive)
Chrome iron (passive)
302, 303, 304, 321, 347 stainless steel (passive)
316, 317 stainless steel (passive) (Parker stainless steel fittings are passivated)
Carpenter 20 Cb-3 stainless (passive), Incoloy 825
Silver
Titanium (passive), Hastelloy C & C276 (passive), Inconnel 625 (passive)
Graphic
Zirconium
Gold
Platinum
+ Anodic
(least noble)
corroded
- Cathodic
(most noble)
protected
Electric current flows from plus to minus
Direction of attack
Table U5 — Electromotive or Galvanic Series for Metals
corrosion is very high. Aluminum, being more anodic metal,
will corrode in this combination.
As a general guideline, if the metals are half the length of
the chart or more apart, the combination should be avoided.
Also, it is not a good idea to combine an anodic metal part
with thin cross section, such as thin wall tubing, with a
cathodic or less anodic metal part of a heavy cross section,
such as a fitting.
Example: A thin wall brass tube with steel fitting is a better,
although not ideal, combination than a thin wall steel tube
with brass fitting.
The susceptibility of different base metals to corrosion while
in contact, depends upon the difference between the con-
tact potentials, or the electromotive voltages of the metals
involved. The greater the potential difference is, the greater
is the tendency for corrosion. The metal with the higher
potential forms the anode and is corroded. The larger the
separation distance in the electromotive chart between the
two metals in contact, the higher the contact potential and
chances for corrosion. For example, zinc and aluminum are
very short distance apart in the chart; therefore potential for
corrosion when these two metals are in contact is very low.
On the other hand, aluminum and passivated 316 stainless
steel are far apart; hence, when in contact, the potential for