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Tinplate corrosion resistance depends heavily on pH. Tin sits in the middle of the electrochemical series. Consequently, it resists neutral foods well, but it dissolves in strong acids and attacks in strong alkalies. Buyers who specify tinplate for the wrong pH range get pinholes and rust within months. Here is how it performs across the pH spectrum.

pH 4–7: The Safe Zone

Tinplate performs best in mildly acidic to neutral conditions:

• Canned vegetables (pH 5–6).
• Fruits (pH 3.5–4.5).
• Meat and fish (pH 6–7).

Consequently, standard 2.8/2.8 g/m² tinplate handles these foods for 2–5 years on the shelf. Furthermore, internal lacquer adds protection for the more acidic items.

pH Below 4: Acidic Attack

Strong acids dissolve tin. Tomato juice (pH 4.2) attacks slowly. However, vinegar, citrus concentrates, and pickling brines (pH 2–3) dissolve tin quickly. Consequently, these foods need:

• Heavier tin (5.6/2.8 or 11.2/11.2 g/m²).
• Full internal lacquer (epoxy phenolic).
• Refrigerated or shorter shelf life.

Without lacquer, even heavy tin fails in acidic products within months.

pH Above 9: Alkaline Attack

Tin resists weak alkalies (soaps, seawater) well. However, strong alkalies (caustic soda, ammonia) etch tin and form soluble tinates. Consequently, tinplate fails quickly in cleaning-in-place (CIP) systems using hot caustic. Furthermore, alkaline detergents leave residues that dull the tin surface.

Temperature Accelerates Everything

At room temperature, corrosion is slow. At retort temperature (121°C), corrosion speeds up dramatically. Consequently, canned acidic foods need heavier tin and lacquer. Furthermore, tinplate is not suitable for continuous high-temperature service above 150°C.

When Tinplate Cannot Handle the Environment

For strong acids, chlorides, or high temperatures, tinplate fails. Instead, solid corrosion-resistant alloys are the answer:

• Hastelloy C-276 Plate handles mixed acids and chlorides.
• Inconel 601 Plate resists high-temperature oxidation.

These alloys cost 10× tinplate, yet they last decades where tinplate fails in months.

Specify pH and Temperature on Your PO

A complete order reads: “T3, 0.20 mm, 5.6/2.8 g/m², epoxy phenolic internal lacquer, for tomato products pH 4.2, retort 121°C.” Leave out the food pH and you receive general-purpose stock.

Get the Right Corrosion Protection

Tell us your food or chemical type and operating temperature. We will recommend tinplate grade or suggest a nickel alloy if tinplate cannot handle it.

• Email: vera.liang@ztwysteel.com
• Location: Xishan District, Wuxi, Jiangsu, China
• Supply range: tinplate substrates, nickel alloys, copper, electrical steel
• Documentation: MTC with coating weight, lacquer type, and migration test
• Compliance: EU 1935/2004, FDA 21 CFR, GB 4806

We reply within one working day.