Outer ring of hot-dipped galvanized steel coils of white rust control measures of defects

After passivation, the hot-galvanized steel with good corrosion resistance, with the enhancement of environmental awareness, trivalent chromium passivation or chromium-free passivated replaced hexavalent chromium passivation, becomes an important process of hot-dip galvanizing production. Trivalent chromium passivation, occasionally appears in the outer ring of white rust corrosion of steel roll, analysts believe the reason for the film thickness of thin, PMT coil when the temperature is too low, as well as packaging and environment temperature is too large. Control measures are as follows:

1, optimization of passivation and drying process
1) on hot galvanizing process parameters of roller coating machine for standardizing regulations, including roller coating machine for coating, the relative speed of the roller and the roller pressure.
2) increase passivation concentrations to increase film thickness.
3) increase passivation of PMT after temperature, set the hot air temperature inside the oven at 220 c or more.
4) to increase the speed of drying the cooling fan, tried to reach room temperature before the plate in coil.
2, strict inspection standard

Increased product testing frequencies, galvanized surfaces Cr3+ coated by Spectrophotometric method for measurement, detects the frequency increased from class 1 to class 2 and salt spray tests also increased from 1 specimen per class 3~4 class to each sample, for later product quality tracking.
3, strengthening equipment maintenance
Strengthening on the roll and dip coatings roller machining precision control, paint roller and dipped the roundness of the roll control within 0.02 mm. Strengthen the maintenance of parts such as roller bearings, clutch, prevent the rollers in turn produced in the process of beating, affects the coating uniformity.
4, temperature control packaging and quality

Strict control of the temperature of the coil packaging, coil packaging must be indoors after a long enough time, make the same temperature as the room temperature to prevent the water temperature in the coil surface condensation. Meanwhile, steel coil surface must be dry before packing, paper, plastic film and packaging must be in strict accordance with requirements for packaging, to enhance its seal, to prevent rain or moisture from entering during storage and transport.
In conclusion, through the optimization of passivation and drying process, measures to reduce the temperature coiling and packaging, elimination of outer ring of white rust of steel roll defects, guarantee the quality of products.

Source: http://www.goldensunsteel.com/