Minimox^™ Alloy Surface Treatment

Alloy Self-Protection

Alloys designed for high-temperature applications contain certain additions. Research at Material Interface has shown if those addition elements are instead applied as a superficial nanocrystalline coating to the surface of a more basic alloy, the same high-temperature surface oxidation properties can be achieved.

Minimox^™ alloy surface treatment is the result of the research. The product is:

• Single component process
• Water-based
• Can be applied in the field without special equipment (spray, brush, dip)
• Can be applied in and on complicated geometries
• No volatile hydrocarbons
• Pennies/sq foot

The surface treatment nucleates alloy self-protection.

What is self-protection?

In alloys that are "self-protected," the composition of the ultimate protective coating is primarily a function of alloy, not the coating material. After treatment with Minimox^™ nanoparticle solution, resulting thermal oxides have:

1. Better chemistry, and

The enhanced chromium at the surface is due to a change in the surface chemistry of the alloy - there is no chromium in Minimox^™ solution. The alloy protects itself.

2. Better structure

Uncoated 600	Coated 600
Fewer voids and protrusions in the Minimox™-treated and oxidized surface result in fewer nucleation sites for crevice corrosion.

Oxidation Resistance

Minimox™- coated and Oxidized	Uncoated

The reduction of oxide scale growth at elevated temperatures is demonstrated on these samples of coated vs. uncoated 410 stainless steel oxidized at 850^°C.

In cross section, these samples show the uncoated sample had a 450µm oxide while the coated sample had a minimal oxide layer.

Minimox™- coated and Oxidized, 10X	Uncoated, 10X

This reduction of oxide scale growth at elevated temperatures occurs after Minimox^™-treatment on a wide variety of stainless, aluminum, nickel and superalloys. All of the alloys shown below were dipped in Minimox^™ and heated to 850^°C (1560^°F) for 24 hours.

This is a 304 stainless bowl heated to 927^°C (1520^°F), for 3 hours/cycle, 3 cycles. The left side (golden) was coated with Minimox^™ nanocrystalline surface treatment; the right side was uncoated and shows spalling and excessive oxidation.

Heat-treating Pretreatment

One application for the technology lies in a heat-treating pretreatment for martensitic stainless steels. The sample below shows a section of 410 stainless that was heat treated 1037^°C (1900^°F) 1 hour followed by tempering at 760^°C (1400^°F) for 4 hours.

Untreated             Treated with Minimox^™

Additional Applications

• Reduction of metal dusting
• Hot salt exposure
• Stress corrosion cracking
• Room temperature electrochemical testing
• Aluminum corrosion