Martensitic stainless seamless steel pipe

A martensitic stainless seamless steel pipe comprising:

• a chemical composition consisting of, in mass %,
• C:
• 0.030% or less,
• Si:
• 1.00% or less,
• Mn:
• 1.00% or less,
• P:
• 0.030% or less,
• S:
• 0.0050% or less,
• Al:
• 0.001 to 0.100%,
• N:
• 0.0500% or less,
• O:
• 0.050% or less,
• Ni:
• 3.00 to 6.50%,
• Cr:
• more than 10.00 to 13.40%,
• Mo:
• 0.50 to 4.00%,
• V:
• 0.01 to 1.00%,
• Ti:
• 0.010 to 0.300%,
• Co:
• 0.010 to 0.300%,
• Ca:
• 0 to 0.0035%,
• W:
• 0 to 1.50%, and
• with the balance being Fe and impurities, and satisfying Formula (1), and
• a microstructure containing, in volume ratio, 80.0% or more of martensite, wherein
• an inner surface of the martensitic stainless seamless steel pipe has a depassivation pH of 3.50 or less in an aqueous solution that contains 5 mass % of NaCl and 0.41 g/L of CH3COONa and further contains CH3COOH:
• Cr+2.0Mo+0.5Ni+0.5Co≥16.0 (1)
• where, a content of a corresponding element (in mass %) is substituted for each symbol of an element in Formula (1).