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"Yellowing in electroplated tin on aluminum"

February 26, 2010

Good afternoon,

I need your help so that we can solve the problem of yellowing / oxidation in various locations outside the bushings after applying acid tin with the following composition:

Bath Tin Tin methane sulphonate = methane sulfonic acid + + Additive Plutino

Analysis 23/02/10 Sn = 37.2 g / l Acidity = 259.0 g / l Sn control Range = 30 to 40 g / l Acidity = 250 to 300 g / l

Following the automatic tinning line:

Recipe for alloy aluminum alloy Recipe for Bronze

Chemical degreasing degreasing chemical
Electrolytic electrolytic degreasing Degreasing
3 washes 3 washes
Methane sulfonic acid activation = activation = 10% Sulfuric Acid 20%
3 wash 3 wash
Activation = methane sulfonic acid 1% xxxxxxxxxxxx
Tin Tin Bath Bath
3 washes 3 washes
Hot Water Hot Water
Oven drying oven drying

Important notes:

1 - The yellowing occurs in bushings (aluminum alloy) in the recipe for tinned aluminum alloy, because when these same tin bushings bronze in revenue this yellowing does not occur (where the outside of the sleeve is steel and the inner aluminum or bronze) .
2 - Parts tinned bronze in revenue yellowing does not occur.
3 - We are applying a aperagem at least twice the normal amperage, because the rectifier coseguirem not rectify the corrente.Já are buying filters for rectifiers to remedy the problem.
4 - In the bathroom is not being made to organic (Resorcinol 1.5 Kg / Shift + Additive Plutino 600 ml / Shift ANTAROX and 100 g 1 time / week) as was being done to the bath base fluoborate Tin + Acid Fluobórico . Please check what the possible problems that would have to do is go back to organic in the bath today.
5 - Note that at the point where the yellowing, almost no deposition estanho.The pictures attached (Ok = layer normal and po = Points where almost no tin deposition and oxidation possible points).

First 2 pictures "Okay"


Last 2 pictures "PO"

6 - There was also need to increase the flow of water washes.
7 - What are the possible problems if the two tin alloys in a single recipe (bronze alloy), since for now we are not having problems.

Francisco Dias
chemical technician - São Paulo, Brasil

March 1, 2010

I did not understand your use of revenue and a word that was aspergem (or something).
I ran a MSA tin line for a couple of years and it would yellow in a few weeks if it was not rinsed in DI water.

James Watts
- Navarre, Florida

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