Page 464 - 4300 Catalog Cover.pdf

U12 Parker Hannifin Corporation
Tube Fittings Division
Columbus, Ohio
http://www.parker.com/tfd
4300 Catalog General Technical
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 T4
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) Phospher 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 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
the potential for 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 contact po-
tentials, or the electromotive voltages of themetals 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.Inotherwords, the larger theseparationdistance
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; thereforepotential for corrosionwhen these twometals are
in contact is very low. On the other hand, aluminum and passiv-
ated 316 stainless steel are far apart; hence, when in contact,