Sodium Acetate

Sodium acetate is a ….

Weak alkaline, buffer substance for the pH stabilisation of organic dyebaths and other buffer solutions.

Anhydrous sodium acetate

  • Is a weak alkaline buffering agent
  • Should (or must) be added to many anodising dyeing baths
  • Stabilises the pH range
  • Improves even adsorption of the organic dye across the metal surface
  • Some deeper tones can be created by using it
  • Only 5-7 g/L buffer additive is required

Requirements

As the pH value unavoidably changes during dyeing (e.g. due to anodising acid introduced, water hardness, evaporation etc.) buffer substances are often added as a matter of preference to the dye bath. These guarantee stable pH values over an extended period and help to ensure the identical colouring of the end products. Local pH variations in dyeing baths (minor bath movement, complex shaped parts) can be reduced by using buffer additives.

Major pH value deviation in a system without buffering influences adsorption of dyes and their fastness to light. If a small concentration of dye is used in the bath the buffering substance ensures even adsorption of the dye.

Application

Typical quantity used : 5-8 g/L

Dissolve the sodium acetate in five times (5x) the amount of water then pour the mix into the dye bath. Adjust the pH value as required using acetic acid. When strengthening the dye bath add sodium acetate in proportion to the dye addition.

Example
Dye bath with 10g/l Deep Black MLW. If 1 kg of dye is added to the bath (at 10g/L this equals a water quantity of 100 litre) then 500 g of sodium acetate (5g/L) should also be added.

According to the manufacturer the following anodising dyes must be buffered:

  • Deep Black MLW liq
  • Turquoise PLW liq
  • Grey NL liq

The following anodising dyes benefit from being buffered:

Orange3LW liq
Red B3LW
Green 3LW
Deep Black H3LW
Fast Gold L
FieryRed ML
Bordeaux RL
Violet CLW
Green LWN
Bronze G
Bronze 2LW
FastBronze L
Brown GSL
Yellow Brown 2G
Olive Brown 2R
Yellow 3GL
Red GLW
Red RLW