Descaling and Activating Stainless Steel

Question:

Our stainless steel parts are severely scaled after welding. We use a 30 percent nitric acid solution containing acid fluoride salts for descaling. Adding hydrochloric acid or raising the temperature caused etching. How can the scale be removed faster without etching?

Answer:

Use a 15 percent sulfuric acid solution and add a small amount of your descaling bath. Heat this bath to 120° F and immerse your parts for a few minutes before transferring them to your nitric acid descaling bath.

Question:

How can stainless steel be activated before chromium plating while avoiding solutions containing chloride ions?

Answer:

After degreasing by alkaline spray cleaning or soak cleaning, stainless steel can be activated by immersion for one minute in a solution prepared with 200 to 500 mL/L of sulfuric acid at 65 to 75° C. (Prepare the solution slowly to avoid splashing.) An alternative procedure uses a cathodic treatment at 5 A/ft2 for 1 to 5 min in a solution at room temperature prepared with 50 to 200 mL/L of sulfuric acid. Water rinsing in two or three successive tanks will be needed after activation.