FI109488B - Corrosion resistant pipe and process for its manufacture - Google Patents

Description

1 109488

Corrosion resistant tube and method for its manufacture

The invention relates to a corrosion-resistant tube made of copper or copper alloy according to the preamble of claim 1.

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When copper and copper alloys come into contact with water, a certain amount of copper dissolves. In principle, this is corrosion. However, this copper donation generally does not go so far as to cause a real corrosion hazard. However, the health effects of copper leaching, particularly in drinking water systems 10, have recently been the subject of increasing environmental awareness. Germany, for example, is likely to tighten the existing benchmarks in the future (3 mg Cu / 112 hours stagnation time) and Europe will probably set even stricter benchmarks. In Germany, these guidelines are generally not exceeded at present. Exceptions may be new systems or unfavorable water quality.

Many publications are known which describe the internal corrosion protection layers of pipes. These are relatively thick layers of about 1 to about 200 µm, which are plastic / resin or metal. For example, plastic / resin coatings are sprayed (DE-OS 3 038 084), applied by coating devices not disclosed (EP 0 299 408) or similar materials are applied during or after cold forming: · : as an apology (DE-PS 4 110 584). Metallic coatings consist of main •; ·; in the case of tin, which is applied by chemical separation (EP-A 0 503 389, JP-OS 4-45 282) or by a special heating / cooling process in a high frequency furnace (DE-OS 3 823 309). All of these went. These methods are laborious and usually involve additional work steps that need to be integrated into the normal manufacturing process and therefore expensive. In addition, plastic / resin coatings generally do not have sufficient heat resistance and, on the other hand, are susceptible to swelling and under-migration of the material, which may result in an adhesive strength of. '1: The problem. Small faults can cause underdrain and local corrosion.

»» · ·. ···. It is therefore an object of the invention to provide copper or copper alloy

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· '35 made of corrosion-resistant tubing with reduced copper deposition with a suitable protective layer.

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2,109,488

The invention solves this task by selectively inserting the elements chlorine, phosphorus, silicon and sulfur individually or in combination into a tube to form a coherent modified surface layer of a few molecules, wherein these elements are chemically bound or adsorbed on the surface of the substance. first from the surface in the direction of the substrate at a proportion of 0.1 to 4 atomic percent by weight (the rest of the oxygen, carbon and alloy constituents), traverses near the surface through a maximum of 5-50 atomic weight by weight and drops toward the substrate to unavoidable concentrations; the evolution of the elemental concentration in the q ker-10 can be represented by the following equation: "3: X 3jCjQ _o y ci (X) = ci0e + —--- xea'X, 1 'aiXtemax 15 where q: elemental i content, qo: elemental i concentration on the layer surface, q max: maximum depth of the concentration XiCmax, 20 x: penetration depth,

Xic max- 'place of maximum concentration of elemental i, a *: constant depending on additives and elements (see Figure 1).

: · · J (The total concentration is obtained as the sum of the individual concentrations.) 1 * »25 The curve q (x) is shown in Figure 1.

• · · •> M (

Organic-based corrosion inhibitors for use in: ;; * in the heat exchanger industry and refrigeration systems, often containing sulfur, but also '' phosphorus, chlorine or silicon atoms or compounds. Simply dispensing these inhibitors into a system that delivers a barrier creates an interface between substance and medium. ·· a potentially reversible deposit for the teddy bear that follows the laws of temperature and pressure dependence of adsorption events. The inhibitory molecules fed are applied in a selection of:. . without reacting to the surface of the substance through supportive measures such as pressure, kit, '·· *, kan, temperature, etc. They are therefore only effective in closed systems, 35 since in open systems they do not attach sufficiently firmly to the substance to be protected and thus migrate again over time. Furthermore, they cannot be used in the food sector.

3, 109488

The modified surface layer according to the invention preferably contains chloride, phosphate, silicate, siloxane, sulfide and / or sulfate moieties, in particular the sulfide / sulfate ratio is from 2: 1 to 4: 1.

5 Only substances that are in ionic form in water, contained in naturally-formed surface layers, or permitted in the drinking water treatment / food industry, shall be introduced so as to avoid additional chemical loading of the water.

Depth profiles are prepared by XPS (= X-Ray Photoelectron Spectroscopy = X-ray Spectroscopy) after various ion bombardment removals to obtain information on the altered surface layer and concentrations within this layer. The layer thickness D is only a few atoms. The thickness D of the layer is primarily 15-100 nm, and the elements chlorine, phosphorus, silicon and / or sulfur are deposited on the upper part of the surface layer of about 10 nm. Depending on the 15 elements, the highest concentration is preferably at a depth of about 1-5 nm. The concentration gradually drops to zero in the direction of the substrate, and the concentration of copper or other alloys increases accordingly until the substrate is finally reached.

The process for producing a corrosion-resistant pipe according to the invention is characterized in that one or more elements chlorine, phosphorus, silicon and sulfur are added individually or in combination to the lubricant used in the pipe forming (drawing) process and these additives are modified at least at different temperatures: ··· : by thermal activation in the regions. Activation takes place at different temperatures and at different times, depending on the additives used, • the type of dressings and the binding energy.

• · ·. 25 Depending on the temperature, hard, semi-hard or soft tubes are formed.

. When atoms / molecules interact with one another or with an interface,;:; in order to allow the formation of bonds, various structural and energetic conditions must be met. The atoms on the surface of the body produce outwardly a certain (boundary) surface energy due to their unsaturated valences. By binding to these free valences, foreign atoms / molecules can interact with this interface.

. ·· '. A free atom can in principle provide free valences in all directions, but the same does not apply to a surface bound atom. It uses only • · i .: for one-way connection. Again, the number of coordination points at the edge or corner atom using ':': is greater. It follows that the number of unsaturated valences and surface energy, and thus also the number of reaction possibilities, increases with increasing vacancies and micro-roughness.

In the case of the invention, the surface of the material is mechanically loaded during molding, i.e. errors are made in the microstructure. The surface is "activated" in this way. The additives to be modified are transferred by means of a lubricant under pressure to the activated surface on which they react, supported by the molding heat released. Initially, a chemical reaction layer is formed. In the simplest case, a single molecule layer is formed. It can grow as a result of subscriptions and networking-10 actions. However, farther away from the substrate, bonding forces and dipole interactions induced by adjacent compounds diminish, crosslinking reactions are reduced, and the reaction layer is gradually converted to an adsorption layer. This complex layer structure is much more tightly bound to the parent metal due to the chemical bond than the layer physically adsorbed on the metal surface alone, and is not washed away by temperature, pressure variations, and flow effects.

As additives, organic substances according to the groups of compounds mentioned in claims 7 to 10 can be used.

In particular, calcium-containing compounds are preferred because they facilitate carbonate incorporation. This promotes the formation of the desired carbonate protective layer, which is generally formed depending on the conditions of use and consists mainly of: * ·: calcium and copper carbonate.

·· *. The total amount of additives in the lubricant is 0.2-40% by weight, preferably 0.5-10% by weight. The additive (s) can be reacted both by molding heat (during molding heat generated during the drawing process and subsequently by a corresponding heat treatment. Alternatively, the additional heat treatment takes place at 100-850 ° C, preferably 200-600 ° In C, under shielding gas In addition to the individual effects, the synergistic * · ': effects of the elements chlorine, phosphorus, silicon and sulfur and the mode of attachment in the additive are important.

• v. Additives may additionally react at room temperature for a few days to weeks. - · ·. 35, which corresponds at least to the time that usually elapses between leaving the semi-finished plant and being installed at the customer.

:: The advantages of the method described are that it can be added to the manufacturing process used without the hassle of working. The thin surface layer, unlike the bulky layers, is characterized by good adhesive strength, which is due in particular to the fact that the layer is attached to the substrate by chemical change. In addition, neither bending nor joining processes such as soldering, screwing or pressing are affected.

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The invention will be further illustrated by the following embodiment.

For this purpose, a 15 x 1 mm copper mounting tube was prepared, using standard traction oil for the first strokes and special oil with 2% by weight of sulfur for the last three strokes. As sulfur carrier, calcium sulfonate (Ca (SO 3 -R) 2) was added to the traction oil as an additive. The heat treatment was carried out in a continuous oven at 400 ° C / 2h under shielding gas.

Copper Dispensing Test Method: 15 A stagnation test was performed in the laboratory on 0.5 m long tubes (regular water change every 24 hours except on weekends and holidays. Determination of copper content in water samples which were then discarded and then filled again with fresh water).

20 Standard SF copper tubes (hard, shiny) serve as reference points.

Water sample A (averages): Water sample B (averages): pH = 6.7 pH = 8

: ··· GH = 4.2 ° dH GH = 4.9 ° dH

; ·; KH <1 ° dH KH = 2.5 ° dH

··. ' 25 S042 '= 56 mg / L S042' = 2 mg / L

Cl '= 8 mg / L Cl' = 60 mg / L. · t. (GH = total hardness; KH = carbonate hardness; ° dH = German hardness) »· • · * ·

Results: 30 Copper donation has decreased after 42 days of trial in both waters tested compared to the reference values. Concentrations in water A are <1 mg Cu / l (Figure 2), in water B predominantly <0.5 mg Cu / l (Figure 3).

. · · ·. Using the tubes according to the invention would therefore leave the current (German) ': 35 even when tightening to 3 mg Cu / l, for example 1.5 mg Cu / l, for a certain variation (cf. the horizontal line in Fig. 2/3). .

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Figure 4 shows the concentration curves of sulfur (a.), Sulfur carrier calcium (b.) And copper (c.) Obtained by XPS (X-ray spectroscopy) over the modified surface layer.

In particular, they show that Equation 5 according to the invention (claim 1) is an excellent representation of the sulfur concentration curve.

Claims (17)

1. Corrosion resistant pipe of copper or a copper alloy, the pipe surface of which is protected by a protective layer, characterized in that by regulating the incorporation of the elements chlorine, phosphorus, silicon and sulfur individually or in combination, a few molecules of thick, modified surface layer are formed. in which these elements are chemically bonded or adsorbed to the material surface, whereby the total concentration of said elements in this layer increases from surface to base material, starting from a percentage of 0.1 to 4 atom percent (the remainder oxygen, carbon dioxide). and alloying elements), in the surface area within a range of 10 nm, a maximum of 5-50 atomic percent is passed, and against the base material it drops to levels of inevitable impurities, and the concentration process q of the individual elements within the layer can be described by the following reaction: ___ "aix. AiCiO -a, x ci (X) - ° ί0® + · x · e, 1. aixic 1 max where q: concentration of the element i, Cjo: concentration of element i at the surface of the layer, Q max: concentration maximum in depth xic max, x: penetration depth, * * xic max: location of maximum concentration for element i, 4 · S a,: additive and element dependent constants ( compare Figure 1). 25 Corrosion-resistant pipe according to claim 1, characterized in that the surface layer contains: chloride, phosphate, silicate, siloxane, sulfide and / or sulphate parts. Corrosion-resistant tube according to claim 2, characterized in that the sulfide / sulfate -...: ratio in the layer is from 2: 1 to 4: 1. Corrosion resistant according to one or more of claims 1-3, characterized in that the thickness of the modified surface layer D = 15-100 nm. Corrosion-resistant pipe according to claim 4, characterized in that the elements are chlorine, 1! ' '. phosphorus, silicon and / or sulfur in the surface area of the modified surface layer are enriched over a range of about 10 nm and their maximum concentration is at a depth of about 1-5 nm. u 109488 Process for producing a corrosion-resistant pipe according to one or more of claims 1-5, characterized in that the lubricant used in the conformational (drawing) process of the pipe is provided with one or more additives which decompose the elements chlorine, phosphorus, silicon and sulfur individually or in combination and that these additives are reacted by at least one thermal activation in different temperature ranges. Process according to claim 6, characterized in that chlorine-releasing additives from the group of compounds of chloro paraffins, hydrochloride-containing olefins or fatty acid esters with disulfur dichloride are used. 10 Process according to claim 6, characterized in that phosphorus-releasing additives from the group of compounds of phosphorus-containing zinc-organyls, phosphoric acid esters or phosphonic acid derivatives are used. 15 9. A process according to claim 6, characterized in that silicon emitting additives from the group of compounds of silicone polymers are used. Process according to claim 6, characterized in that sulfur-emitting additives from the group of compounds of organic sulfides, polysulfides, sulfur-containing zinc-organyls, sulfur-treated olefins, sulfur-containing fats, sulfonic acid derivatives, chlorine-sulfur-treated olefins or fatty acid esters with disulfuric dichloride. 11. A method of producing a corrosion-resistant pipe according to one or more of claims 1-5, wherein the surface layer is formed by incorporation of sulfur, characterized in that during the reshaping (drawing) process, the tube used with the lubricant •: ··: is supplied with elemental sulfur and is reacted by at least one thermal: activation in different temperature ranges. • # « Method according to one or more of claims 6 to 11, characterized in that the proportion ... 30 of additives in the lubricant accumulate to 0.2-40% by weight. »· *; The method according to claim 12, characterized in that the proportion of additives is added to::: 0.5-10% by weight. '. 35 Process according to one or more of claims 6 to 13, characterized in that the additives are reacted by the heat generated during the conversion (drawing) process. * * 12 109488 Process according to Claim 14, characterized in that the additives are reacted by a heat treatment connecting to the conversion (drawing) process at 100-850 ° C. 5 Process according to claim 15, characterized in that the heat treatment is carried out at 200-600 ° C. Process according to one or more of claims 14-16, characterized in that the additives react after a period of time from a few days to vector at room temperature. > »· I · * 1 · * 1 # * ·» »*» I * 1 I '· * t · 1