Grauer & Weil, leaders in the metal finishing industry in the Indian sub-continent, are constantly endeavoring to induct new technologies and offer the latest facilities and services to the Surface Treatment industry. Backed by a rich experience of more than five decades, our Research & Development department has the privilege of introducing many "Firsts" in the Plating industries of our country. In keeping with this tradition, we have joined hands with M/s. Nippon Dacro Shamrock Company of Japan to introduce the world famous 'Dacrotizing' processes in India. 'Dacrotizing provides outstanding protection to metallic surfaces, against corrosion. This famous coating known by the name 'Dacromet' consists of inorganic silver grey deposits comprising Zinc and Aluminum flakes, uniformly eistributed on the entire substrate.
DACROMET is applied by a three-stage process
As with every surface treatment, DACROTIZING requires a perfect surface cleaning. A mechanical preparation is generally proffered but chemical cleaning can also be approved for many types of components.
Parts to be treated in bulk or on racks are covered with a wet film by immersing in a cold aqueous dispersion, without any electrolyte action. The use of a pneumatic electrostatic spray gun is an alternative method of applying the coating.
The final structure of the coating is achieved by curing at about 300 0C. This advantage develops the properties of adhesion and corrosion, resistance for the film.
Two coats are a minimum for bulk dip-spin treatment. Parts treated by other coating methods can have either a single or multiple layers.
ADVANTAGES OF DACROTIZING
NO HYDROGEN EMBRITTLEMENT
Mechanical surface preparation (degreasing + abrasive cleaning) prevents any risk of hydrogen embrittlement during the entire process.
When chemical surface cleaning is used, the curing at 300 C. and the non crystalline structure of the coating ensure the absence of embrittlement.
During the dipping processes also the internal surface of parts are protected, e.g. spring pins, small assemblies, clips, etc.
PROTECTION OF THE ENVIRONMENT
DACROTIZING is almost a pollution free process.
No air pollution (only aqueous products), water pollution is limited only to the surface cleaning stage and the periodic cleaning of coating equipment (e.g. baskets).
PROPERTIES OF DACROTIZED PARTS
Under normal atmospheric conditions, the DACROTIZED coating provides very long life which is proportioned to the thickness of the coatings itself.
At equivalent coating weights, DACROMET has a corrosion resistance superior to many other systems. This resistance is due to the barrier effect created by the overall coverage of zinc and aluminium flakes and to the sacrificial protection of zinc controlled by the aluminium in the coating and by the chromate passivation throughout the film.
Indeed, compared to other zinc coatings, the internal passivation of DACROMET considerable reduces the formation of white rust (zinc corrosion products).
As with all sacrificial coatings, corrosion protection by DACROMET is proportional to the quantity of coating applied.
In practice, two grades have been standardized
- Grade A : min 24g/m2 = (approx. 5 )
- Grade B : min 36g/m2 = (approx. 8 )
- N.B : Up to 25 can be applied if required.
RESISTANCE TO 5% NEUTRAL SALT SPRAY TEST (ASTM B 117, BS 7479, DIN 50021)
DACROMET performances considerably exceed the requirements specified by the automobile industry
- Min. 250 hrs. without white rust
- Min. 500 hrs. without red rust
- Min. 250 hrs. without white rust
- Min 1000 hrs. without red rust
These performances remain unchanged after a heat treatment of 8 hrs. at 260 C.
RESISTANCE TO CYCLIC TESTS
DACROMET conforms to the different cyclic tests used by the automobile industry (3C Renault, P-VW 1210 VW / Audi, APGE, CCTI2, etc.
RESISTANCE TO KESTERNICH TEST (DIN 50018-SFW 2.0 S)
This test is an acidic attack on the coating. Therefore, the resistance is directly proportional to the coating weight. Depending on the parts, coating thickness of 8 to 10 provides a resistance superior of 3 cycles or more.
RESISTANCE TO BIMETALLIC CORROSION
Excellent performances in contact with aluminium, chromium, zinc and tin; but less corrosion resistance with stainless steel, copper, nickel and lead.
Properties of DACROTIZED parts are maintained up to about 280 C. DACROMET is therefore perfectly suitable for parts in the engine compartments of vehicles.
RESISTANCE TO ORGANIC PRODUCTS
Excellent resistance to solvents, fuel and hydraulic fluids. DACROMET is an electrically conductive coating.
The DACROMET film can be covered by a paint film which has direct metal adhesion (e.g. DACROKOTE).
USE OF THE DACROTIZING PROCESS
DACROTIZING WILL PROTECT
Steel, particularly high strength steels normally sensitive to hydrogen emrbrittlement.
Some sintered metals.
Aluminium and some of its alloys.
It is used for protection of small parts (screws, clips, nails, springs, etc.), but also for important parts such as (brake discs, chains, containers, pallets, etc.)
It has been developed principally within the automobile industry but is being extended to other industries such as house-building and appliance industries, etc.
LIMITS OF USE Some visible contact marks may occur on flat surfaces treated in bulk by dip-spin method.
Parts have to accept curing at approx. 3000C
Limited ductility restricts further plastic deformation (crimping-bending) but is entirely adequate for the protection of parts which deform elastically, i.e. springs and clips.
* In Collaboration with Nippon Dacro Shamrock Co., Ltd.
- Alfa Romeo 9.57511
- Audi Tl 245
- BMW N600 00.0
- Chrysler Corporation PS-5873
- Citoren B 15 3312
- Fiat 9.57511
- Ford WSD-M21P13
- Motors Corporation GM 6173-M
- Honda Motor Co. HES D 2008
- Jaguar JMS 10.22.05
- Lancia 9.57511
- Mazda Motor Co. MES CG 311C
- Mercedes-Benz DBL 9440 & 8440
- Nissan Motor Co. NES M 4052
- Opel 4256
- Peugeot B 15 3312
- Porsche PN 11 003
- Renault 01-71-002
- Rover Group Ltd. RES.21.ZS.05
- Seat Tl245
- Suzuki Motor Co. SES D 2204
- Toyota Motor Co. TS H 7700
- Volkswagen TL 245
- Volvo STD 5752,52
- AFNOR (F)
- British Standard (GB)
- UNI (I)
- *ABB (Sweden) 20620034-5
- *Bechtel Power Corp. 12259C-121A&C-121B
- *Bendix Corporation ES-1825
- *Bendix (Allied Automotive) 5.J.01.16
- *Bendix Heavy
- *Vehicle Systems BW-254-P
- *Bosch N67F 603 31
- *Caterpillar 1 E 675
- *Colt Industries Operating
- Corp. Holley Carburetor
- Division 31206
- SP 11 C
- *Delco Moraine DM-7308
- *Delco Moraine NDH
- Stakpole MS4316
- Merriman MS4314
- *Electricite de France X MA04 01 T1
- *Eurotunnel (Climaneu) C46 000 MVT
- NYJX 2723/1
- *Fiamm Q-1C-033
- *Fuji Heavy Industries TS 430-9-4
- *General Electric Company F 71H1-S
- *Girling T.S. 2-21-101
- *Hino Motor B-4-1-24
- *Isuzu Motors ISC B 22-003
- *ITT Automotive (A. Teves) ATE N 106 36
- *Iveco Standards 18-1101
- *John Deere LAN 930
- *Kelsey-Hayes MS-104025
- *Lucas Standards 17-550-13A&B
- *Mercury Marine M-1-24-P & D
- *Div. of Brunswick Corp.
- *North American Lighting
- Engineering Specification ENG-036
- *Piaggio 2827
- *Renault Vehicules
- Industriels 01-71-4002
- *Roper Corporation 301533
- *Saab-Scania STD 2883
- *S.I.G. SIG 17.226
- *Sulzer Q 049-24-034
- *Unbrako P.47 VI A.2
- *Valeo 2 519 222
- *Wabco Westinghouse JED 378
- Friedrichshanfen AG ZFB 811
- BS 7371
All information, recommendations and suggestions appearing in this literature concerning the use of our products are based upon tests and data believed to be reliable. However, it is the user's responsibility to determine the suitability for his own use of the products described herein. Since the actual use by others is beyond our control, no guarantee expressed or implied is made by GROWEL as to the effects of such use of the results to be obtained, nor does GROWEL assume any liability arising out of use, by other, of the products referred to herein.
Nor is the information herein to be construed as absolutely complete since additional information may be necessary or desirable when particular or exceptional conditions or circumstances exist or because of applicable laws or government egulations. Nothing herein contained is to be construed as permission or as a recommendation to infringe any patent.
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