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SANODURE BLACK CRO
Sanodure® Black CRO
Homogeneous black dye with rapid adsorption for the dyeing of anodized aluminium.
Sanodure® Black CRO is of primary interest for finishing processes in which rapid dye adsorption is
desired and the fastness properties are of secondary importance.
Only recommended for interior use.
1. Dye-specific properties
Commercial form : black fine powder
Chemical character : homogeneous azo dye, metal-free
Storage stability : virtually unlimited (close package tightly after removal of dye)
Bulk density : 830 g/l
Solubility in water at 20°C : 40 g/l
Shade : black (not suitable for grey shades)
Intrinsic pH : 6-9 (at 10 g/l)
Ecotoxicological data : see Safety Data Sheet.
2. Application conditions
Concentration, dyeing temperature and time
Concentration Dyeng temperature Dyeing time
Standard coatings (>10 µm) 10 - 20 g/l 25 - 60°C 10 - 30 min
Continuous coatings (3-5 µm) 20 - 30 g/l 50 - 80°C 2 - 5 min
Dyeing pH : 7.0 ± 0.5
Adjustment and correction of the pH : with acetic acid or dilute caustic soda
Water quality : preferably deionized
Stability of the dyebaths : avoid pH values below 6 (gel-like precipitates are
formed, tinctorial strength falls off)
Sealing : preferably with Anodal® ASL (one or two stage).
3. Preparation of the dyebath
When preparing the dyebath care must be taken that the dye is dissolved well.
The dye is preferably dissolved in a separate container with hot water (80-90°C) (1 part to ca. 5
parts water). This stock solution is then stirred into the dyebath.
4. Scope of application
Sanodure® Black CRO is particularly recommended when the finishing process calls for rapid
adsorption of the dye and the fastness properties are of less importance.
This dye is of special interest for the following applications:
- short time dyeing
- cold dyeing
- dyeing of continuously produced oxide coatings (coil anodizing or similar thin coatings)
- dyeing of cast parts of high silicon content
- dyeing of oxide coatings with low adsorption power.
For building elements which require light and weather resistant finishing anodized to a coating
thickness of 20 µm or more, the following special dyes are recommended:
For exterior architectural aluminium (by the Sanodal process) :
Sanodal Deep Black MLW
Sanodal Black GL Paste
Sanodal Deep Black H3LW
Sanodal Deep Black HBL Liquid
5. Remarks on application
5.1 Behaviour in cold dyeing
With 20 g/l Sanodure® Black CRO deep black dyeings can be produced under standard
conditions at room temperature.
5.2 Effect of entrained foreign substances in the dyebath
Foreign substances Sensitivity
Aluminium ions and sulphates little sensitivity
Chromic acid tinctorial strength declines
5.3 Strengthening the dyebath
A reduction in tinctorial strength caused by impurities can be made good by adding fresh dye,
provided it is within the normal limits.
5.4 Behaviour of dyeings in the sealing solution
Sealing solution Bleeding
deionized water medium
with Anodal® ASL low
Note: cold dyeings tend to bleed more heavily than others.
5.5 Prevention of mould formation :
An addition of an antimicrobial product can inhibit mould formation for a long time. We
recommend the addition of Nipacide CI 15 (See Technical Information) 25 – 50 mg/l.
6. Fastness and other properties of the dyeings
6.1 Light fastness (ISO 2135)
GS Standard 12 µm (20 g/l, 60°C, 15 min) 3-4
GS Standard 20 µm (20 g/l, 60°C, 20 min) 7-8
Continuous coatings 3-5 µm 2-3
6.2 Heat stability
- Assessment: poor (rating 2, red-brown)
- Test conditions: coating thickness 12 µm
dyeing conditions 10 g/l, 20 min, 60°C
sealing with Anodal® ASL
time 2 h at 200°C
6.3 Strippability of unsealed dyeings
Unsealed dyeings are virtually unstrippable in diluted nitric or sulphuric acid.
They can be stripped in nitric acid 10 % + potassium permanganate 5 %.
After the treatment in Potassium permanganate, neutralization must be carried out for 1-5 min
in a sodium bisulphite 5 % solution.
Dyeings which have aged for a few days are not strippable. Freshly produced.
7. Disposal of spent dyebaths
Spent dyebaths must be disposed of with Anodal® WT-1 Liquid. The precipitation method is
described in the Technical Information bulletin for Anodal® WT-1 Liquid.
The table below gives the dosages necessary for precipitating Sanodure® Black CRO:
Precipitation FeCl3, 40% Etching lye Anodal® WT-1 Residual dye
ml/g dye ml/g dye ml/g dye Liquid in the filtrate mg/l
A 1.0 - 0.7 < 1
B 1.0 - 0.7 < 1
C - 1.0 0.7 < 1
Many of their dyestuffs, pigments and chemicals are patented by Clariant in numerous industrial countries.
® Trademark of Clariant registered in numerous countries.
®* Trademark registered in numerous countries and licensed to Clariant.
®+ Other Manufacturer's registered trade mark
The signs ®, ®* and ®+ appear only at the first mention of the product.
The information and recommendations presented here were compiled with the utmost care, but cannot be extended to cover
every possible case. They are intended to serve as non-binding guidelines and must be adapted to the prevailing conditions.