ASTM D4042 Test Method for Sampling and Testing for Ash and Total Iron in Steel Mill Dispersions of Rolling Oils
3. Summary of Test Method
3.1 Polyethylene disposable sample bags in a suitable holding device are used to collect representative samples of nonhomogeneous dispersions of rolling mill oils in water from an operating mill coolant system.
3.2 The collected sample and disposable bag are analyzed as one for ash and total iron.
3.2.1 Ash content is determined gravimetrically by evaporating all water from the sample bag before heating the residue and bag in a muffle furnace to a constant weight (Test Method D482).
3.2.2 Total iron content is determined by digesting the iron in the ashed sample and bag in an acidified solution. The iron in the solution is reduced with stannous chloride and titrated with standardized potassium dichromate.
3.2.3 The ash and total iron contributed by a sample bag alone are determined separately and are subtracted from the values of bag and sample to obtain the values for the sample alone.
NOTE 1 - There are a number of alternative methods available for determining total iron in an ashed solution such as Test Methods D2795 and D1068.
4. Significance and Use
4.1 The life cycle and cleanliness of a recirculating steel mill rolling oil dispersion is affected by the amount of iron present. This iron consists mainly of iron from acid pickling residues and iron from attrition of the steel sheet or rolls during cold rolling. In sampling rolling oils for total iron it is difficult to prevent adherence of iron containing sludge to the sample container. Thus, the accuracy of a total iron determination from an aliquot sample is suspect. This practice provides a means for ensuring that all iron contained in a sample is included in the analysis.
4.2 Although less significant, the ash content is still an essential part of the procedure for obtaining a total iron analysis. Generally, the ash will be mostly iron, and in many cases, could be used as a substitute for total iron in determining when to change the dispersion.
