A customer currently uses a Competitor Product at 1.0% to aid in descaling steel in their HCl pickle line. The competitor product is described as both an acid inhibitor and an accelerator. The typical line conditions are 9.7% HCl (w/v), 12% Fe2+ (w/v) at 195°F. The customer submitted a steel sample of steel for evaluation to determine if Actispeed 600 would be a viable alternative to the Competitor Product. The submitted steel contains many micro-craters and rolled in scale from the hot mill. The rolled in scale defect can cause issues in further processing of the steel including, but not limited to, cosmetic defects and improper adhesion of coatings
When received by Harry Miller Corp, the steel sample was cut into 0.875-inch X 3-inch panels and the edges were smoothed on a grinding wheel to remove all burrs. As a result, there were 25 viable panels for evaluation. Each panel was stamped with an alpha ID and cleaned in odorless mineral spirits and acetone. After cleaning, each panel was weighed to 0.0001g. The surface quality of the steel was observed at 40X magnification before descaling. The image below is of panel ID “L.”
Circled in red is an example of the rolled in scale present on the submitted steel. The goal for this evaluation was to quickly and efficiently remove the rolled in scale while still providing adequate base metal protection.
Descaling/ Rolled in Scale Removal
Four panels were selected at random to be pickled under each inhibitor condition to determine the rate of scale removal. All pickle liquor was comprised of 9.7% HCl (w/v), 12% Fe2+ (w/v) at 195°F. The evaluated inhibitor conditions were: uninhibited, 1.0% Competitor Inhibitor, 0.5% Actispeed 600, and 1.0% Actispeed 600. Each inhibitor was added by weight of 20°Be HCl.
To determine the completion of descaling, each panel was observed under 40X magnification every 10 seconds of descaling until all surface scale and rolled in scale was removed. The photographs below show the descaling progress at 20 seconds.
Results of 20-Second Descaling
Uninhibited- Panel ID: I
Competitor Inhibitor @ 1.0% (w/v)- Panel ID: M
Actispeed 600 @ 0.5% (w/v)- Panel ID: O
Actispeed 600 @ 1.0% (w/v)- Panel ID: X
% Efficiency/ Base Metal Protection Determination
Panels were pickled in fresh pickle liquor composed of 9.7% HCl (w/v), 12% Fe2+ (w/v) with the inhibitors as mentioned below. All testing was performed at 195°F. Percent base metal loss was evaluated at 15 minutes and 30-minute pickling intervals.
15-Minute % Efficiency Study
After the 30-second descaling evaluation, the panels were put into fresh pickle liquor for 15 minutes. Each panel was rinsed in tap water and acetone then weighed to 0.0001 g.
30-Minute % Efficiency Study
For this evaluation, fresh pickle liquor was made and a new set of panels were used. The Panel ID’s were: V, S, U, T, E, and W. All panels were rinsed in tap water and Acetone after pickling then weighed to 0.0001 g.
From the % Efficiency Studies, Actispeed 600 at 0.5% provides good % Efficiency at greater than 90% while Actispeed 600 at 1.0% provides the same base metal protection as the Competitor Product. From the descaling studies, all panels were completely descaled after 30 seconds. All scale was removed from the Actispeed 600 panels by 20 seconds while the Competitor Product panel still had rolled in scale in the deeper craters.
The below image compares the surface finish of panels after the 30 minute % Efficiency was completed. All tested panels have an improved surface finish over the uninhibited panel. However, panels tested in Actispeed 600 have the brightest end finish.
From left to right: L- Untested panel with scale V-panel pickled without inhibitor S- Competitor Product@ 1.0% E- Actispeed 600 @ 0.5% W- Actispeed 600 @ 1.0%