1.Are carbon steel/stainless steel lined with fiberglass recommended?
Not recommended.
Problem: Cold rolling pickling uses high-temperature hydrochloric acid, which has extremely strong chloride ion penetrating power. If there are pinholes in the fiberglass (FRP) lining of carbon steel, the hydrochloric acid will instantly corrode the carbon steel substrate, causing perforation within days.
Current situation: Only used in the rinsing section or in older sulfuric acid pickling methods.
2.What are the key considerations when selecting granite/acid-resistant ceramic tiles?
Selection Criteria:
Material:
Must be Qingdao Bluestone or Jinan Bluestone (diabase), dense and crack-free.
Sandstone is strictly prohibited; its high porosity poses a risk of leakage.
Grouting:
Grouting joints are a weak point. Potassium silicate grout or furan resin grout is required.
Avoidance: Ordinary cement grout will inevitably leak within 7 days.
Temperature: Excellent temperature resistance (>150℃), no aging.
Lifespan: Over 20 years.
Dangers:
Heavy, requires a high-quality foundation.
Difficult to detect leaks: Acid seeps into the grout joints, not leaking externally, but directly corroding the foundation steel reinforcement.
Repairs require shutdown and stone chiseling, with a construction period measured in weeks.
3.How about Hastelloy C276?
Applications: Pickling of titanium and titanium alloys, laboratory applications, and high-temperature areas with very small volumes.
Cold-rolled hydrochloric acid lines rarely use C276 because:
Price: C276 is a nickel-based alloy, costing over 100 times more than PPH.
Unnecessary: While hydrochloric acid is indeed resistant to C276, the pickling temperature of cold-rolled carbon steel is not high (<100℃), making PPH and granite perfectly adequate.
Exceptions: Occasionally, C276 is used as a lining for localized protection in acid regeneration and concentration areas (high temperature, high chloride ion, abrasive).
4.How to decide on the selection of a cold rolling pickling tank?
First, consider the temperature:
Acid temperature ≤90℃ → PPH (best value for money).
Acid temperature 90-100℃ → Granite or imported high-temperature PPH (manufacturer's temperature resistance report required).
Acid temperature >100℃ → Only granite/acid-resistant bricks are suitable.
Next, consider the volume/length:
Extra-long tanks (>40 meters) → Granite segmented (uniform thermal expansion).
Short tanks/underground vessels → PPH (fast manufacturing, easy maintenance).
Finally, consider the maintenance access:
Production lines that cannot tolerate long-term shutdowns → PPH modularization is recommended; if damaged, remove one piece and replace it with a spare.
Can accept a maintenance period of more than half a month → Granite.
5.Regardless of the material chosen, what must the tank structure adhere to?
Classic failure example: A beautifully laid granite paving surface was exposed, with the underlying concrete directly contacting the granite.
Result: A small leak occurred in the grout joints, allowing acid to seep into the concrete, causing it to expand, powder, and ultimately collapse.
Correct approach: A fiberglass (vinyl ester resin) waterproofing layer must be applied to the bottom of the granite paving, with the granite resting on top of the fiberglass.