Faster, Simpler Pickling of Stainless Steel
SURFACE OPTIMIZED FOR PAINTING
A common problem resulting 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 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 has been performed for stainless steel processed this way on an EPS line. Roughness levels of some samples were even higher than the R110 level range we normally recommend. To review the full results of this testing > click here. <
Stainless Steel does not use hydrochloric acid for pickling. Instead, it uses 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.
That creates opportunities for service centers to purchase hot rolled stainless and pickle it 'in-house' prior to slitting or blanking, for greater value added. In addition, they can 'optimize' the surface roughness, allowing their customers to obtain better paint performance (see box at right ) for even more value added.
Economics of EPS for Stainless
The composition of the scale found on hot rolled stainless steel is different than carbon steel and more difficult to remove. For EPS, that simply means more exposure to the Slurry Blast stream is needed. This is accomplished by slowing the strip travel through the line.
To assess the economics of EPS processing of stainless, it is helpful to use the EPS Operations Cost Calculator. The Calculator is calibrated for processing of both carbon steel and stainless steel – you select which material you wish to analyze by using the 'Material Type' input cell.
Even though EPS stainless variable costs are higher than EPS carbon variable costs, EPS pickling of stainless should be more profitable than EPS pickling of carbon steel. This is because stainless pickling revenue is proportionately higher than its higher variable cost.
A coil of ATI 2102® alloy emerges from the EPS Cell at Stripco.