---
title: "Hard Anodising for Engineering Components — Wear, Fit & MIL-A-8625 | Saravana Consultancy"
description: >-
  Hard anodising for pneumatic and hydraulic components, textile machinery and defence supply in India: coating thickness inside bores, dimensional growth, chiller capacity, PTFE impregnation and MIL-A-8625 qualification.
canonical: "https://www.saravanaconsultancy.in/applications/engineering-components-anodising"
source_url:
  html: "https://www.saravanaconsultancy.in/applications/engineering-components-anodising"
  md: "https://www.saravanaconsultancy.in/applications/engineering-components-anodising.md"
last_modified: 2026-08-20
---

# Hard anodising for engineering components — wear, fit and proof

On an engineering component the finish is a dimension, a hardness and a friction coefficient. Three problems recur: thickness inside a bore, dimensional growth on tolerance, and the chiller that actually caps your throughput.

On engineering components the finish is not cosmetic. It is a dimension, a hardness, and a friction coefficient. Hard anodising to [MIL-A-8625](/blog/mil-a-8625-anodising-india) Type III is specified because the part has to resist wear, hold a seal, or run against another surface without galling — and because the specifier can point to a test.

## What gets hard anodised

In India the demand concentrates in pneumatics and hydraulics — cylinder tubes, valve spools, pistons, actuators — in textile machinery, particularly cone pulleys, in machine tools, and in automotive and aerospace components. Coimbatore, Pune and Rajkot are the dense clusters.

## The three problems that recur

### Thickness inside a bore

Current density falls away inside a cylinder bore, so the coating thins exactly where the seal runs. Auxiliary cathodes and agitation design, not more current, are the fix.

### Dimensional growth

Hard anodising grows the part by roughly half the coating thickness per surface. On a tolerance-critical component that has to be in the drawing, not discovered at assembly.

### Cooling capacity

Type III runs cold and draws heavy current. Chiller capacity is what actually caps your current density, and therefore your cycle time and your throughput.

### Proving it

Customers increasingly ask for evidence, not assurance: [Vickers hardness per ASTM B578](/blog/hard-anodize-hardness-test-astm-b578-vickers), [salt spray per ASTM B117](/blog/astm-b117-salt-spray-test-anodize), and Taber wear per ASTM D4060.

## PTFE impregnation

Where a part needs hardness and lubricity — sliding components, valve spools, anything running dry — the answer is a PTFE-impregnated hard anodise. We have covered the stack in [hard anodizing with PTFE](/blog/hard-anodizing-ptfe) and the [process and wear test methods](/blog/ptfe-impregnation-hard-anodize-process-test-methods).

## Defence and aerospace supply

The Ministry of Defence has notified successive Positive Indigenisation Lists, and the SRIJAN portal has carried more than 33,000 items offered for indigenisation with over 15,700 completed. For a Tier-2 supplier, the surface finish specification is frequently the qualification barrier rather than the machining: MIL-A-8625 conformance has to be demonstrated, documented and repeatable. See the [compliance checklist](/blog/mil-a-8625-compliance-checklist-india) and [chromic acid Type I](/blog/chromic-acid-anodising-mil-a-8625-type-i-aerospace-india).

## What a general rack line costs

Set the archetype to **General rack** in the [plant cost and payback calculator](/calculators/anodizing-plant-cost) and enter your longest component. For most engineering work that is 0.3–2 metres, which makes this the second cheapest of the four plants to build — though Type III adds chiller and rectifier cost that Type II does not carry.

If you know the plant you want and need the numbers before a serious internal conversation, the [plant setup snapshot](/services/plant-setup-snapshot) is a ₹2,500 written feasibility note in three working days, credited against Phase 0.