Specs

Understanding Metal Finishing Specifications: Why They Matter and How to Read Them Correctly

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In the metal finishing world, specifications are far more than paperwork—they are the backbone of quality, consistency, and compliance. Whether you’re applying anodize, electroless nickel, zinc plating, passivation, or any other coating, the ability to understand and interpret specifications directly determines the reliability of the finished product and the level of trust earned from customers.

This article covers two essential topics:

  1. Why understanding specifications is critical

  2. How to read and interpret metal finishing specifications correctly

1. Why Understanding Specifications Is Critical

Specifications define the process – not the technician

Every job begins with a specification. It tells you what must be done, how it must be done, and what the finished part must achieve. Without the spec, you are relying on tribal knowledge or assumptions—both of which introduce risk. Specifications ensure:

  • Correct pretreatment steps

  • Required coating thickness

  • Proper rinsing and process-control parameters

  • Acceptable appearance and performance criteria

  • Testing requirements (adhesion, corrosion resistance, hydrogen embrittlement relief, etc.)

A misunderstanding of even one clause can lead to rework, scrap, customer complaints, or worse—field failures.

Specifications protect customers and suppliers

Specs represent the agreement between the manufacturer and the finishing shop. When followed properly:

  • The customer gets a part that performs as engineered.

  • The finisher gets clear boundaries and acceptance criteria.

Ambiguity disappears. Expectations align. Everyone wins.

Specifications evolve – and staying current matters

Many finishing specs (AMS, ASTM, MIL, ISO) are updated frequently to reflect new science, improved testing methods, or updated compliance standards. Using an outdated version can result in:

  • Incorrect thickness requirements

  • Obsolete process steps

  • Noncompliance with industry or regulatory bodies (Nadcap, FAA, DoD, etc.)

Staying current is not optional—it’s part of delivering quality.

They drive process control and certification

Specifications serve as the reference point for:

  • Calibration and testing procedures

  • Correct baking cycles for hydrogen embrittlement relief

  • Chemical maintenance frequencies

  • Tank parameters and inspection points

  • Internal quality audits and Nadcap checklists

Your internal procedures must match the governing specs, or you risk audit findings, failed inspections, or production delays.

2. How to Read and Understand Specifications

Specifications can feel dense at first glance, but they follow predictable structures. If you approach them methodically, they become clear and manageable. Here’s how to break them down.

Step 1: Start with the Scope

The Scope section tells you:

  • What the spec applies to

  • What types of materials it covers

  • What coating or process it governs

  • Any major exclusions or limitations

If the job doesn’t fall within the scope, you may be using the wrong specification entirely.

Step 2: Look at the Applicable Documents

Many specs reference other documents such as:

  • AMS2750 (pyrometry)

  • AMS2759/9 (hydrogen embrittlement relief)

  • ASTM B117 (salt spray testing)

These are not optional—they’re required to be followed. Understanding how these documents interact is critical to compliance.

Step 3: Understand the Technical Requirements

This is the heart of the specification. It details:

  • Pretreatment

  • Plating/anodizing parameters

  • Coating thickness

  • Appearance

  • Microstructure requirements

  • Types of allowable brighteners, stabilizers, or additives

  • Prohibited conditions or contaminants

Every requirement tells you what “right” looks like.

Step 4: Read the Process Notes and Tables Carefully

Many specs include:

  • Thickness tables

  • Current-density guidance

  • Temperature and pH ranges

  • Stress-relief requirements

  • Post-treatment steps (baking, sealing, passivation, etc.)

Technicians often overlook notes beneath tables—yet those notes often change the entire meaning.

Step 5: Identify Quality Assurance and Testing Requirements

Most finishing specs include mandatory tests such as:

  • Adhesion

  • Salt spray / corrosion resistance

  • Hardness

  • Conductivity

  • Coating weight

  • Hydrogen embrittlement relief verification

Understanding these helps ensure the process is producing finishes that meet engineering expectations.

Step 6: Check the Notes and Appendices

The back of the spec is often where the most important clarifications live:

  • Explanations of exceptions

  • Definitions of key terms

  • Guidance for special conditions

  • Restrictions on high-strength steels

  • Details on process variations

A single footnote can determine whether a process passes or fails an audit.

Step 7: Confirm Revision Level

Always verify:

  • Revision letter or year

  • Customer-required revision (which may differ from the latest published version)

Finishing the job to the wrong revision—even if the process is technically correct—is still considered nonconforming.

Final Thoughts

Understanding specifications is one of the most important skills in the metal finishing industry. It ensures:

  • Consistent quality

  • Compliance with engineering and regulatory requirements

  • Reduced scrap and rework

  • Better communication between customer and supplier

  • Increased shop capability and credibility

Specs are not just rules—they are tools. When read carefully and applied correctly, they empower your team to deliver finishing work that is reliable, repeatable, and fully aligned with customer expectations.