How do you calculate coating yield for rare earth magnets?

Divide conforming coated magnets by total magnets coated and multiply by 100. With 8 conforming out of 250, yield is 8 / 250 x 100 = 3.2%.

What is a good coating yield for NdFeB magnets?

A well-controlled Ni-Cu-Ni or epoxy line typically holds 93-98% conformance. The 3.2% default result sits 91.8 points under a 95% target, which points to a bath or pretreatment failure rather than normal scatter.

Why do rare earth magnets fail coating?

Common causes are poor pretreatment leaving surface oxides, porous sintered substrate that traps gas, bath chemistry drift, and inadequate rinse leading to blistering. Any of these can fail adhesion or leave thin spots that corrode.

Coating yield vs powder yield: what is the difference?

Powder yield is an upstream metric on loose milled powder, while coating yield is at the finishing stage on nearly complete magnets. A failure at coating is far costlier because the part carries all prior processing cost.

How do I improve coating yield?

Stabilize pretreatment and activation, tighten bath temperature and chemistry control, seal porous substrates before plating, and verify thickness and adhesion on a sampling plan so drift is caught early.

Does coating yield include reworkable parts?

Set that by policy: magnets that can be stripped and recoated may count as conforming after rework, but if stripping risks the substrate or costs too much, count them as failures so the metric reflects real loss.

Rare Earth Magnet & Motor Materials calculator

Coating Yield Calculator

Coating yield measures how many NdFeB magnets come off the plating or e-coat line meeting adhesion, thickness and coverage spec, as a percentage of everything coated. Because sintered neodymium magnets corrode rapidly without protection, the nickel-copper-nickel, epoxy or Everlube layer is not optional, and a coating defect means the whole finished, magnetized part is at risk of rust or field failure. Surface-finishing and quality engineers track this metric because a rejected magnet at coating has already absorbed all the powder, pressing, sintering and machining cost, making it one of the most expensive places to lose a part. The gap to target shows whether pretreatment and bath control are holding.

What this calculator does

Estimate coating yield for rare earth magnet and motor materials using production-ready inputs so teams can track KPI performance and decide whether corrective action is needed.
Use it when coating yield in rare earth magnet and motor materials needs a clean rate and gap-to-target you can put on a tier board.
It computes the share of coated magnets meeting adhesion, thickness and coverage spec, and how many points that sits below your target.

Formula used

Coating yield rate = coating yield count ÷ total coating yield population × 100
Coating yield gap to target = coating yield rate - target coating yield rate

Inputs explained

Conforming coated magnets (pass adhesion and thickness):
Total magnets processed through coating line:
Target coating yield rate:

How to use the result

Use it after each coating batch or as a daily roll-up to watch plating-bath health and pretreatment consistency.
A pass/fail count treats a pinhole reject and a full adhesion failure the same, so it does not tell you which defect mode is driving losses.

Current U.S. benchmarks

The producer price index for copper and brass mill shapes stands at 559.593 (BLS, May 2026), up 76.8% from a year earlier. Quotes priced off last quarter's material cost miss this move. Global copper trades at $13,484 per tonne (IMF via FRED, May 2026).
The U.S. has 5,397 electrical equipment and appliances establishments employing about 369,437 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate coating yield for rare earth magnets? Divide conforming coated magnets by total magnets coated and multiply by 100. With 8 conforming out of 250, yield is 8 / 250 x 100 = 3.2%.
What is a good coating yield for NdFeB magnets? A well-controlled Ni-Cu-Ni or epoxy line typically holds 93-98% conformance. The 3.2% default result sits 91.8 points under a 95% target, which points to a bath or pretreatment failure rather than normal scatter.
Why do rare earth magnets fail coating? Common causes are poor pretreatment leaving surface oxides, porous sintered substrate that traps gas, bath chemistry drift, and inadequate rinse leading to blistering. Any of these can fail adhesion or leave thin spots that corrode.
Coating yield vs powder yield: what is the difference? Powder yield is an upstream metric on loose milled powder, while coating yield is at the finishing stage on nearly complete magnets. A failure at coating is far costlier because the part carries all prior processing cost.
How do I improve coating yield? Stabilize pretreatment and activation, tighten bath temperature and chemistry control, seal porous substrates before plating, and verify thickness and adhesion on a sampling plan so drift is caught early.

Last reviewed 2026-05-12.