Difference between Inflexible and Ironclad

INFLEXIBLE vs IRONCLAD: NOUN

A naval vessel having the parts above water covered and protected by iron or steel usually in large plates closely joined and made sufficiently thick and strong to resist heavy shot. Modern naval vessels are made of steel throughout, and this term is only used in historical contexts.
A naval vessel cased or covered wholly or partly with thick iron or steel plates, generally having a heavy backing of wood, so armored to resist projectiles or the attacks of rams or other armored vessels.
A 19th-century warship having sides armored with metal plates.
A metal-plated ship, vessel, or vehicle
An armor-plated warship.
A wooden warship of the 19th century that is plated with iron or steel armor

Resistant to being bent
Not willing to change, e.g. one's opinion or habits; obstinate; stubborn; resolute; determined.
Incapable of change; unalterable; immutable.
Firm in will or purpose; not to be turned, changed, or altered; resolute; determined; unyieding; inexorable; stubborn.
Not capable of being bent; stiff; rigid; firm; unyielding.
Refusing to change one's attitude, purpose, or principles; immovable.
Incapable of being changed; unalterable.
Not easily bent; stiff or rigid. : stiff.
Not making concessions
Incapable of adapting or changing to meet circumstances
Extended meanings; incapable of change
Incapable of change
Literal meanings

Not flexible; incapable of bending or of being bent; rigid: as, an inflexible rod.
Unyielding in temper or purpose; that will not yield to prayers or arguments; firm in purpose; incapable of being turned; not to be prevailed on.
Not to be changed or altered; unalterable; not permitting variation.
Synonyms Rigid, stiff.
Inexorable, inflexible, resolute, steadfast, unbending, unyielding, immovable, unrelenting; obstinate, stubborn, dogged.

Covered or cased with iron plates, as a vessel for naval warfare; armor-plated.
Figuratively, very rigid or strict; constructed, as a form of words, so as to allow no evasion or escape, or permit no flaw to be detected.
Noting an electrical apparatus or machine in which the iron part of the structure completely or partly surrounds and thereby mechanically protects the electric conductors: as, an iron-clad armature, one having the conductors embedded in slots or holes.

Fossilized, Flinty, Stiffened, Adamant, Inexorable, Ironclad, Adamantine, Stiff, Uncompromising, Unadaptable, Unyielding, Ossified, Unbending, Intransigent, Rigid

Peremptory, Hard, Armored, Treaty, Mandatory, Rigorous, Stringent, Rigid, Brassbound, Incontestible, Inflexible, Incontestable, Unassailable, Watertight, Unshakable

Fossilized, Flinty, Stiffened, Adamant, Inexorable, Ironclad, Adamantine, Stiff, Uncompromising, Unadaptable, Unyielding, Ossified, Unbending, Intransigent, Rigid

Peremptory, Hard, Armored, Treaty, Mandatory, Rigorous, Stringent, Rigid, Incontestible, Brassbound, Inflexible, Incontestable, Unassailable, Watertight, Unshakable

For Verizon to be so inflexible is horrible!
In trust planning, irrevocable no longer means inflexible.
We called Regents and the staff was inflexible.
An inflexible, categorical rule neglects these additional considerations.
Offers fall apart when both sides are inflexible.
Long cable is inflexible and gets kinked easily.
Development and validation of the inflexible eating questionnaire.
Identified by Dialogue Partners: The dialogue partners reported that inflexible federal workplace policies create the following issues for womenwho have caregiving responsibilities: Inflexible workpla
For example, a family which is rigidly inflexible toward relationship roles would be expected to be rigidly inflexible in the disciplining of children.
Inflexible parents, inflexible kids: A sixyear longitudinal study of parenting style and the development of psychological flexibity in adolescence.

So no ironclad assurances can be made to the client.
And to make your case, you need ironclad arguments.
Customer need not download or even license Ironclad software.
Please note, however, that such privileges are not ironclad.
You have an ironclad firewall and antimalware system.
This falls somewhat short of an ironclad rule.
Ironclad Securitythemselves safe from a variety of threats.
Russian Technological Transfers: Naval Modernization and Ironclad Development.
Ironclad pitch excited Loughlin about leading the round.
There is no clear end to the ironclad period, but towards the end of the 1890s the term ironclad dropped out of use.