U.S. patent application number 10/391906 was filed with the patent office on 2003-09-25 for method for reducing copper solubility at the inner surface of a copper tube.
Invention is credited to Baukloh, Achim, Priggemeyer, Stefan, Reiter, Ulrich, Triquet, Christian.
Application Number | 20030178107 10/391906 |
Document ID | / |
Family ID | 27771523 |
Filed Date | 2003-09-25 |
United States Patent
Application |
20030178107 |
Kind Code |
A1 |
Baukloh, Achim ; et
al. |
September 25, 2003 |
Method for reducing copper solubility at the inner surface of a
copper tube
Abstract
In a method for reducing copper solubility at the inner surface
of a copper tube, the process parameters surface treatment
(degreasing and pickling), flow conditions (flow speed<1 m/s),
temperature (50.degree. C. to 80.degree. C.) and time (1 min to 10
min) are purposefully adjusted to one another, so as to achieve a
uniformly directed crystal growth during the course of the tin
coating. In particular, the planes (101) of the copper crystals and
the tin crystals are aligned parallel to one another and the
directions [101] are aligned perpendicular to one another.
Inventors: |
Baukloh, Achim; (Osnabruck,
DE) ; Priggemeyer, Stefan; (Wallenhorst, DE) ;
Reiter, Ulrich; (Osnabruck, DE) ; Triquet,
Christian; (Bissendorf, DE) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
27771523 |
Appl. No.: |
10/391906 |
Filed: |
March 19, 2003 |
Current U.S.
Class: |
148/519 ;
148/536 |
Current CPC
Class: |
C23C 18/31 20130101 |
Class at
Publication: |
148/519 ;
148/536 |
International
Class: |
C22F 001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 2002 |
DE |
102 13 185.6 |
Claims
What is claimed is:
1. A method for reducing copper solubility at the inner surface of
a copper tube, comprising adjusting: surface treatment; flow
conditions, including flow speed<1 m/s; temperature between
50.degree. C. and 80.degree. C., and time between 1 min and 10 min
with respect to one another, so as to achieve a uniformly directed
crystal growth during the course of a tin coating and formation of
a copper/tin phase.
2. The method according to claim 1, wherein the surface treatment
adjusted includes degreasing and pickling.
3. The method according to claim 1, in which the plane (101) of the
tin crystals is aligned parallel to the inner surface of the copper
tube.
4. The method according to claim 2, in which the plane (101) of the
tin crystals is aligned parallel to the inner surface of the copper
tube.
5. The method according to claim 1, in which the plane (101) of the
tin crystals is aligned parallel to the plane (101) of the copper
crystals.
6. The method according to claim 2, in which the plane (101) of the
tin crystals is aligned parallel to the plane (101) of the copper
crystals.
7. The method according to claim 3, in which the plane (101) of the
tin crystals is aligned parallel to the plane (101) of the copper
crystals.
8. The method according to claim 4, in which the plane (101) of the
tin crystals is aligned parallel to the plane (101) of the copper
crystals.
9. The method according to claim 1, in which the planes (101) of
the copper crystals and the tin crystals are aligned parallel to
each other and directions [101] are aligned perpendicular to each
other.
10. The method according to claim 2, in which the planes (101) of
the copper crystals and the tin crystals are aligned parallel to
each other and directions [101] are aligned perpendicular to each
other.
11. The method according to claim 3, in which the planes (101) of
the copper crystals and the tin crystals are aligned parallel to
each other and directions [101] are aligned perpendicular to each
other.
12. The method according to claim 4, in which the planes (101) of
the copper crystals and the tin crystals are aligned parallel to
each other and directions [101] are aligned perpendicular to each
other.
13. The method according to claim 5, in which the planes (101) of
the copper crystals and the tin crystals are aligned parallel to
each other and directions [101] are aligned perpendicular to each
other.
14. The method according to claim 6, in which the planes (101) of
the copper crystals and the tin crystals are aligned parallel to
each other and directions [101] are aligned perpendicular to each
other.
15. The method according to claim 7, in which the planes (101) of
the copper crystals and the tin crystals are aligned parallel to
each other and directions [101] are aligned perpendicular to each
other.
16. The method according to claim 8, in which the planes (101) of
the copper crystals and the tin crystals are aligned parallel to
each other and directions [101] are aligned perpendicular to each
other.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a method for reducing copper
solubility at the inner surface of a copper tube.
[0003] 2. Description of Related Art
[0004] It is known that one can coat the inner surface of a copper
tube with tin, in order to prevent, with the aid of such a tin
layer, copper ions dissolved from the copper from going over into
drinking water, if such a copper tube is being used as a component
of a drinking water line. In this connection, the European
guideline for drinking water regulations should be noted.
[0005] In the methods known up to this point for depositing a tin
layer on the inner surface of a copper tube, only random crystals
are formed. The packing density of the tin crystals was therefore
unsatisfactory. Thus, copper ions are able to go over into the
drinking water by way of the tin layer.
SUMMARY OF THE INVENTION
[0006] It is an object of the invention to create a method that
will ensure a clear reduction of copper solubility at the inner
surface of the copper tube.
[0007] These and other objects of the invention are achieved by a
method for reducing copper solubility at the inner surface of a
copper tube in which the process parameters surface treatment
(degreasing and pickling), flow conditions (flow speed<1 m/s),
temperature (50.degree. C. to 80.degree. C.) and time (1 min to 10
min) are purposefully adjusted to one another, so as to achieve a
uniformly directed crystal growth during the course of the tin
coating and the formation of a copper/tin phase.
DETAILED DESCRIPTION OF THE INVENTION
[0008] The invention recognized that a high packing density of tin
crystals is able to be reached in the case of a directed crystal
growth during the course of the tin coating. The high packing
density of the tin layer leads to a very homogeneous, evenly formed
and most stable copper/tin phase. In addition to that, the tin
layer is deposited evenly and having a thickness of an order of
magnitude of about 0.1 .mu.m to 3 .mu.m, at a low pore number. The
directed crystal growth is achieved by purposeful setting of the
process parameters surface pretreatment (degreasing and pickling),
flow conditions (flow speed<1 m/s), temperature (50.degree. C.
to 80.degree. C.) and time (1 min to 10 min).
[0009] In spite of the fact that, even after a relatively short
operating time, metallic tin can no longer be detected at the tube
surface, still, the property of the low copper solubility because
of the extremely stable Cu/Sn phase is maintained. Tube surfaces
treated according to the invention distinguish themselves by having
a very low copper solubility and a high stability.
[0010] Ascertaining the crystal structure of tin is preferably done
using the results of X-ray diffraction experiments. During the
interaction of the X-rays and the monocrystals, the incident waves
are diffracted in discrete spatial directions on account of the
lattice-like structure of the tin crystals. Whereas the position of
a diffraction direction is determined by the orientation of the
crystal lattice to the primary beam, the lattice dimensions and the
wavelength used, the intensity of the diffracted beam depends on
the distribution of the tin atoms in the unit cell.
[0011] For this purpose, a length section was cut off as a sample
from the copper tube coated with tin according to the invention.
This sample was then slit in the longitudinal direction, and the
longitudinally slit sample was subsequently bent open to form a
flat material. This flat material with the tin coating facing
upwards was then irradiated with X-rays having
lambda(FeK.sub.a)=1.9373 .ANG., the X-ray being directed at the
flat sample at various diffraction angles. The results show that,
at various angles, a high X-ray diffraction intensity was detected,
which proves that the X-rays were reflected close to 100%. It
follows that the tin atoms have a very high packing density. A
satisfactory barrier layer is formed for the copper ions against
transition into the drinking water.
[0012] In an advantageous further design of the basic idea
according to the invention, plane (101) of the tin crystal is
aligned parallel to the inner surface of the copper tube.
[0013] In this connection, it is then further advantageous, if
plane (101) of the tin crystals is aligned parallel to plane (101)
of the copper crystals.
[0014] A further improvement going beyond this is achieved, if
planes (101) of the copper and tin crystals are aligned parallel to
each other and directions [101]are aligned perpendicular to each
other.
[0015] The advantageous tin coating was confirmed by the following
internal comparison investigation:
[0016] A copper tube coated according to the invention was brought
into contact with drinking water for 15 months. As a result of this
contact, a tin hydroxide layer (Sn.sub.3O.sub.2(OH).sub.2) was
formed on the inner surface. From this copper tube a lengthwise
section was removed, cut open in the longitudinal direction, bent
flat, and then submitted to an X-ray irradiation having
lambda(FeK.sub.a)=1.9373 .ANG.. It was thereby determined that the
reflection of the X-rays (X-ray diffraction intensity) was clearly
less than 100%. Thus, one might have assumed that the object of the
present invention was not attained.
[0017] The tin hydroxide layer was subsequently completely removed,
so that the original coating state was present again. That is, on
the copper there was a copper/tin phase (Cu.sub.6Sn.sub.5).
[0018] Then an X-ray irradiation was again carries out, at which
time an almost 100% reflection was found. Thereby the method
according to the invention was fully confirmed in its
advantageousness.
* * * * *