Finishing Publications & Metal Finishing Information Services
Jump straight to:

Finishing Publications Ltd &
Metal Finishing Information Services

Metal Finishing : Surface Engineering : History of Technology : CD-ROM : Books : Online Database :Helpline : Information to help you and your business


A key to Quality, Productivity, Cost-Savings and a Cleaner Environment

Browse the resources listed on the left to see how important Analysis is in maintaining
high quality and maximising profitability in Metal Finishing operations.


We need to know the chemical composition of our process solutions. Putting it simply – what's in there!

How ? We need to take a sample from the solution in the bath, and analyse it, using usually a chemical analysis method, but sometimes a physical method too.

1. Sampling is not a cinch

We have to think carefully about how to take a meaningful sample. The composition of a process bath may differ from top to bottom of a tank, or as between inlet and outlet. The composition may differ when the bath is working and when it is idle. There may be zones in the bath, especially if it is not thoroughly stirred, which are more or less dilute than the rest of the bath. Chemical and electrochemical reactions take place at or around the anodes and the cathodes – sampling too close to these could give the wrong answer.

Don’t short-change the question of sampling. Carry out some simple tests to see whether any of the effects noted above are reflected in the results given by the following analysis.

2. Look after your sample

Try and carry out your analysis as soon as possible after sampling. Don’t let your sample become heated or be exposed to direct sunlight, before analysis. In some cases (e.g with hydrofluoric acid) don’t forget that the solution can react with the container (when this is made of glass) and this will certainly result in a false result. Don’t forget to label each sample. When and where it was taken, maybe who took it. Use a label which won’t wash off by mistake.

These are the main points about sampling - but there’s much more to it, which you might want to read.