Properties and testing

What this section covers

A nickel-phosphorus deposit is not one material. Its structure, hardness, magnetic behaviour, melting point and corrosion resistance all move with the amount of phosphorus co-deposited with the nickel, and the ranges published for low, medium and high phosphorus overlap enough that two shops can both be right and still deliver different parts. The five notes here separate what changes with phosphorus, what changes with heat treatment afterwards, and what changes only in the test report.

The section also covers the two tests that decide acceptance in practice: the salt spray cabinet, whose results are far more useful as a process control than as a prediction of service life, and hardness measurement, where the scale used matters as much as the number.

How to read these notes

Post-plate baking appears twice, deliberately. Baking for hardness and baking for hydrogen relief are different operations with different temperatures and different reasons, and treating them as one is a common way to end up with a part that is hard and still cracks. Each has its own note.

The standards note is a map, not a substitute. It gives the designation, the issuing body and the scope of each document that names an electroless nickel or conversion coating, so that a drawing callout can be traced to the right specification. It does not reproduce the content of standards that are sold rather than published.