めっき技術

Corrosion resistance

Plating with good corrosion resistance can be classified into galvanization using the action of sacrificial anti-corrosion (zinc-plating to iron base) and plating with good corrosion resistance of itself, which is represented by blik (tin-plated iron base). The latter plating excelling in corrosion resistance includes noble metal plating and electroless nickel plating having excellent chemical resistance.
Type of plating Characteristic value Uses
Sacrificial anti-corrosive plating (primary plating or material is electrochemically protected from corrosion by the upper-layer plating film oxidizing slowly) - Zinc plating and zinc-based plating preventing steel materials from rusting (See zinc and zinc alloy plating.)

- Two-layer nickel plating
Potential difference by the difference of sulfur content in the Ni film based on the principle of sacrificial anti-corrosion is used.
The sulfur content in the lower layer of semigloss nickel is 0.005% and that in the upper layer of bright nickel is 0.05%. The plating thickness is approximately 20 – 30μm in total (semigloss:bright = 6:4).
The corrosion resistance of three-layer nickel plating by sandwiching bright nickel containing 0.1 – 0.2% sulfur between the two layers of plating is further improved.
Various metal products
Plating with good corrosion resistance in plating films themselves - Plating with noble metals small in ionization tendency, such as gold, platinum, rhodium, and palladium.
- Chemical-resistant electroless nickel plating, chromium plating, nickel-tungsten alloy plating, etc.
The high corrosion resistance of nickel-based alloy plating originates in the passivation phenomenon of films.
Chemical industry equipment
採用事例
Corrosion resistance
Environment (type of gas) and gas-resistant anti-corrosive plating
(1) Sulfurous acid gas: Tin plating, zinc plating, solder plating
(2) Nitrous acid gas: Gold plating
(3) Hydrogen sulfide: Gold plating, solder plating, tin plating, rhodium plating, zinc plating
(4) Ammonia gas: Silver plating, nickel plating, tin plating, zinc plating