Faster, Simpler Pickling of Stainless Steel
Stainless Steel does not use hydrochloric acid for pickling. It uses the even more hazardous hydrofluoric acid (HF) and nitric acid. That means stainless pickling lines must be dedicated to that product, so there are fewer lines and the cost is higher than pickling carbon steel.
EPS pickling of stainless steel solves these problems. With no acid involved, special facilities, permitting, hazardous material transportation and handling are no longer needed. The EPS line that pickles stainless steel can also run low carbon, high carbon and HSLA with no ‘changeover’ between products. You simply adapt line speed to the product being run.
These grades of stainless steel have been EPS pickled:
- 304, 316
- 409, 410, 412, 420R, 430, 433, 435, 440R
- ATI 825™
- ATI 2102® alloy
- ATI 2205™ Duplex
All except the 409 were unprocessed hot roll black; the 409 was annealed hot roll. None of the material was shot blasted prior to EPS processing.
“We’re launching an exciting new method of how we process our stainless steel material to remove mill scale and rust. This innovative technology, called ‘Eco Pickled Surface’ or EPS, creates an ideal proﬁle for paint adhesion on stainless steel. In addition, it preps the steel better than any acid chemicals currently available for wash systems.”
Central Moloney, Inc.
A Surface Optimized For Painting
A problem from cold rolling of stainless steel is the surface becomes too smooth and presents poor adhesion properties if the stainless is to be painted. To solve the problem and improve adhesion, the stainless surface is roughened by – guess what? – etching with acid !
EPS offers a much better method to improve stainless steel paint adhesion. The EPS production line is simply operated with an elevated turbine RPM. This has the effect of increasing surface roughness for better adhesion. It also produces a very consistent surface texture that yields a more smooth, premium surface appearance after painting.
Paint adhesion testing was performed for stainless steel processed this way on an EPS line. Roughness levels (Ra) of some samples were even higher than the R110 level we normally recommend.
REVIEW THE FULL TEST RESULTS >
The Economics of EPS for Stainless
The scale on hot rolled stainless steel is different than carbon steel and more difficult to remove. For EPS pickling, it requires more exposure to the Slurry Blast stream – accomplished by slowing strip travel through the line. Now, slowing down the line increases variable cost. Despite that, EPS pickling of stainless is still more profitable than EPS pickling of carbon steel. Why? Because stainless pickling’s revenue as a multiple of variable cost is consistently higher than low carbon’s revenue multiple.
To evaluate the economics of EPS processing of stainless for you, try the EPS Operations Cost Calculator. The Calculator models EPS processing of both carbon steel and stainless steel, as well as HSLA and silicon steels.
Taiyuan Iron and Steel Group (TISCO), the world’s largest producer of stainless steel, operates a three-cell EPS pickling line.